2025Activity reportProject-TeamMIND
RNSR: 202224253W- Research center Inria Saclay Centre at Université Paris-Saclay
- In partnership with:Centre CEA-Saclay
- Team name: Models and Inference for Neuroimaging Data
- In collaboration with:Département NEUROSPIN
Creation of the Project-Team: 2022 April 01
Each year, Inria research teams publish an Activity Report presenting their work and results over the reporting period. These reports follow a common structure, with some optional sections depending on the specific team. They typically begin by outlining the overall objectives and research programme, including the main research themes, goals, and methodological approaches. They also describe the application domains targeted by the team, highlighting the scientific or societal contexts in which their work is situated.
The reports then present the highlights of the year, covering major scientific achievements, software developments, or teaching contributions. When relevant, they include sections on software, platforms, and open data, detailing the tools developed and how they are shared. A substantial part is dedicated to new results, where scientific contributions are described in detail, often with subsections specifying participants and associated keywords.
Finally, the Activity Report addresses funding, contracts, partnerships, and collaborations at various levels, from industrial agreements to international cooperations. It also covers dissemination and teaching activities, such as participation in scientific events, outreach, and supervision. The document concludes with a presentation of scientific production, including major publications and those produced during the year.
Keywords
Computer Science and Digital Science
- A3.1.1. Modeling, representation
- A6.2.4. Statistical methods
- A6.2.6. Optimization
- A6.2.7. HPC for machine learning
- A9.2. Machine learning
- A9.2.1. Supervised learning
- A9.2.2. Unsupervised learning
- A9.2.4. Optimization and learning
- A9.2.5. Bayesian methods
- A9.2.6. Neural networks
- A9.2.8. Deep learning
- A9.3. Signal processing
- A9.7. AI algorithmics
Other Research Topics and Application Domains
- B1.2. Neuroscience and cognitive science
- B1.2.1. Understanding and simulation of the brain and the nervous system
- B1.2.2. Cognitive science
- B1.2.3. Computational neurosciences
- B2.6.1. Brain imaging
1 Team members, visitors, external collaborators
Research Scientists
- Philippe Ciuciu [Team leader, CEA, Researcher, HDR]
- Carlo Barbano [INRIA, Starting Research Position, from Nov 2025]
- Mansour Benbakoura [INRIA, Starting Research Position]
- Antoine Collas [INRIA, Starting Research Position, until Jul 2025]
- Chaithya Giliyar Radhkrishna [CEA, Researcher]
- Thomas Moreau [INRIA, Researcher, HDR]
- Bertrand Thirion [INRIA, Researcher, HDR]
- Demian Wassermann [INRIA, Senior Researcher, HDR]
Post-Doctoral Fellows
- Pierre-Antoine Comby [CEA, Post-Doctoral Fellow, from Sep 2025]
- Reuben Dorent [INRIA, Post-Doctoral Fellow]
- Merlin Dumeur [CEA, Post-Doctoral Fellow, from Mar 2025]
- Fateme Ghayyem [INRIA, Post-Doctoral Fellow, until Feb 2025]
- Baptiste Goujaud [INRIA, Post-Doctoral Fellow, until Aug 2025]
- Ce Ju [INRIA, Post-Doctoral Fellow]
- Romain Lacoste [INRIA, Post-Doctoral Fellow, from Nov 2025]
- Matthieu Terris [INRIA, Post-Doctoral Fellow, until Mar 2025]
- Sheng Wang [CEA, Post-Doctoral Fellow, until Jun 2025]
- Houssam Zenati [INRIA, Post-Doctoral Fellow, until Jan 2025]
PhD Students
- Pierre-Louis Barbarant [INRIA]
- Maxime Bertrait [CEA]
- Pierre-Antoine Comby [CEA, until Mar 2025]
- Celestin Eve [UNIV PARIS SACLAY]
- Theo Gnassounou [INRIA, from Sep 2025 until Nov 2025]
- Theo Gnassounou [ENS PARIS-SACLAY, until Aug 2025]
- Gabriela Pilar Gomez Jimenez [INRIA]
- Ambroise Heurtebise [UNIV PARIS SACLAY, until Oct 2025]
- Alexandre Le Bris [INRIA]
- Leticia Levin Diniz [INRIA, from Jul 2025]
- Leticia Levin Diniz [INRIA, from Mar 2025 until Jun 2025]
- Jarod Levy [Meta]
- Qiaoxin Li [CEA, from Sep 2025]
- Virginie Loison [INRIA]
- Sonia Mazelet [CEA]
- Florent Michel [UNIV PARIS SACLAY, until Oct 2025]
- Denis Hernando Nunez Fernandez [CEA]
- Oumaima Ouaalouhoum [CEA, from Oct 2025]
- Joseph Paillard [Roche]
- Caini Pan [CEA]
- Ana Ponce Martinez [INRIA]
- Angel Reyero Lobo [UNIV TOULOUSE III]
- Victoria Shevchenko [UNIV PARIS - CITE]
- Asma Tanabene [CEA]
- Jad Yehya [INRIA, from Apr 2025]
Technical Staff
- Himanshu Aggarwal [INRIA, Engineer]
- Laure Caruso [CEA, Engineer, from Mar 2025]
- Remi Gau [INRIA, Engineer]
- Lionel Kusch [INRIA, Engineer, until Oct 2025]
- Soukaina Tichirra [CEA, Engineer, until Sep 2025]
- Hippolyte Verninas [INRIA, Engineer, from Oct 2025]
- Jad Yehya [INRIA, Engineer, until Mar 2025]
Interns and Apprentices
- Maxence Barneche [INRIA, Intern, from Apr 2025 until Jun 2025]
- Arthur De Rouck [INRIA, Intern, from Jun 2025 until Aug 2025]
- Albane Dourder-Lavie [CEA, Intern, from Feb 2025 until Jul 2025]
- Caterina Galata [INRIA, Intern, from Nov 2025]
- Melvine Nargeot [INRIA, Apprentice, until Sep 2025]
- Lena Oudjman [CEA, Apprentice]
Administrative Assistant
- Marie Enee [INRIA]
Visiting Scientist
- Carlo Barbano [UNIV Turin, until Feb 2025]
External Collaborators
- Thomas Bazeille [THOMAS BAZEILLE, from Jul 2025]
- Antoine Collas [KARAVELA, from Jul 2025]
- David Degras [Univ Massachusetts Boston, until Jun 2025]
- Benoit Dufumier [CEA, from Nov 2025]
- Elizabeth Dupre [UNIV MONTREAL, from Jul 2025]
- Denis-Alexander Engemann [Roche]
- Remi Flamary [LIX, HDR]
- Alexandre Gramfort [Ministère Economie, until May 2025, HDR]
- Jade Perdereau [AP/HP]
2 Overall objectives
The Mind team, which finds its origin in the Parietal team, is uniquely equipped to impact the fields of statistical machine learning and artificial intelligence (AI) in service to the understanding of brain structure and function, in both healthy and pathological conditions.
AI with recent progress in statistical machine learning (ML) is currently aiming to revolutionize how experimental science is conducted by using data as the driver of new theoretical insights and scientific hypotheses. Supervised learning and predictive models are then used to assess predictability. We thus face challenging questions like Can cognitive operations be predicted from neural signals? or Can the use of anesthesia be a causal predictor of later cognitive decline or impairment?
To study brain structure and function, cognitive and clinical neuroscientists have access to various neuroimaging techniques. The Mind team specifically relies on non-invasive modalities, notably on one hand, magnetic resonance imaging (MRI) at ultra-high magnetic field to reach high spatial resolution and, on the other hand, electroencephalography (EEG) and magnetoencephalography (MEG), which allow the recording of electric and magnetic activity of neural populations, to follow brain activity in real time. Extracting new neuroscientific knowledge from such neuroimaging data however raises a number of methodological challenges, in particular in inverse problems, statistics and computer science. The Mindproject aims to develop the theory and software technology to study the brain from both cognitive to clinical endpoints using cutting-edge MRI (functional MRI, diffusion weighted MRI) and MEG/EEG data. To uncover the most valuable information from such data, we need to solve a large panoply of inverse problems using a hybrid approach in which machine or deep learning is used in combination with physics-informed constraints.
Once functional imaging data is collected the challenge of statistical analysis becomes apparent. Beyond the standard questions (Where, when and how can statistically significant neural activity be identified?), Mind is particularly interested in addressing driving effect or the cause of such activity in a given cortical region. Answering these basic questions with computer programs requires the development of methodologies built on the latest research on causality, knowledge bases and high-dimensional statistics.
The field of neuroscience is now embracing more open science standards and community efforts to address the referenced to as “replication crisis” as well as the growing complexity of the data analysis pipelines in neuroimaging. The Mindteam is ideally positioned to address these issues from both angles by providing reliable statistical inference schemes as well as open source software that are compliant with international standards.
The impact of Mindwill be driven by the data analysis challenges in neuroscience but also by the fundamental discoveries in neuroscience that presently inspire the development of novel AI algorithms. The Parietal team has proved in the past that this scientific positioning leads to impactful research. Hence, the newly created Mind team formed by computer scientists and statisticians with a deep understanding of the field of neuroscience, from data acquisition to clinical needs, offers a unique opportunity to expand and explore more fully uncharted territories.
3 Research program
The scientific project of Mind is organized around four core developments (machine learning for inverse problems, heterogeneous data & knowledge bases, statistics and causal inference in high dimension, and machine Learning on spatio-temporal signals).
3.1 Machine learning for inverse problems
Participants:
P. Ciuciu, A. Gramfort, T. Moreau, D. Wassermann
Inverse problems are ubiquitous in observational science. This necessitates the reconstruction of a signal/image of interest, or more generally a vector of parameters, from remote observations that are possibly noisy and scarce. The link between the parameters of interest and the observations is physics, and is commonly well understood. Yet, the recovery of parameters is challenging as the problem is often ill-posed due to the ill-conditioning of the forward model. Machine learning is now more frequently used to address such problems, using likelihood-free inference (LFI) to inverse nonlinear systems, or prior learning using bi-level optimization and reinforcement learning to guide the way to collect observations.
3.1.1 From linear inverse problems to simulation based inference
| Expected breakthrough: Boosts in MR image quality and reconstruction speed and in spatio-temporal resolution of M/EEG source imaging |
| Findings: Development of data-driven regularizing functions for inverse problems, as well as deep invertible and cost-effective network architectures amenable to solve nonlinear inverse problems on neuroscience data. |
Solving an inverse problem consists in estimating the unobserved parameters at the origin of some measurements. Typical examples are image denoising or image deconvolution, where, given noisy or low resolution data, the objective is to obtain an underlying high-quality image. Inverse problems are pervasive in experimental sciences such as physics, biology or neuroscience. The common problem across these fields is that the measurements are noisy and generally incomplete.
Mathematically speaking, these inverse problem can be formulated as estimating from . Here, is an additive noise and is a (generally non-injective) mapping to a lower-dimensional space. For example, in magneto- and electroenchephalography (M/EEG), is a real linear mapping and is considered white and Gaussian, while in magnetic resonance imaging (MRI), is a complex linear mapping and is circular complex white Gaussian. Despite the linearity of and , estimating is a challenging task when the measurements are incomplete, i.e., and the problem is ill-posed. This is often the case due to physical limitations on the measurement device (M/EEG) or the acquisition time (MRI). Moreover, the linear Fourier operator only reflects an ideal acquisition process and part of the acquisition artifacts (e.g. B0 inhomogeneity) can be compensated by considering nonlinear models at the cost of estimating additional parameters along with the MR image.
To tackle these inverse problems, using adequate regularization will promote the right structure for the data to be recovered. Over the last decade the members of Mind have proposed state-of-the-art models and efficient algorithms based on sparsity assumptions 97, 148, 120, 102, 149, 132, 131, 118, 122, 119. MNE is the reference software developed by the team that implements these methods for MEG/EEG data while pysap-mri proposes solvers for MR image reconstruction.
The field is now progressing with novel approaches based on deep learning by either learning the regularization from data in the context of MRI reconstruction 171, 169, or by considering nonlinear models grounded in the physics underlying the data. The team has started to explore this direction using so-called Likelihood-Free Inference (LFI) techniques built on deep invertible networks 172, 130. A particular application has been on diffusion MRI (dMRI), where we have linked the dMRI signal with physiological tissue models of grey matter tissue 130. Still in MRI but in susceptibility weighted imaging, another approach 112 has consisted in directly estimating the B0 field map from non-Cartesian k-space data to correct for off-resonance effects in non-Fourier operators . The Mind project will continue along this direction studying nonlinear simulators of imaging data as building blocks. A key aspect of the work proposed is to exploit knowledge on the physics of the data generation mechanisms.
3.1.2 Bi-level optimization
| Expected breakthrough: Efficient algorithms to select hyper-parameters and priors for source localisation in MEG and image reconstruction in MRI/fMRI. |
| Findings: Bi-level optimization solvers exploiting gradients to scale with the large number of samples and hyper-parameters. |
In recent years, bi-level optimization – minimizing over a parameter which is itself the solution of another optimization problem – has raised great interest in the machine learning community. Indeed, many methods in ML reduce to this bi-level framework, typically the problem of hyper-parameter optimization.
In most practical cases, hyper-parameter selection is done using cross-validation (CV), which basically consists in splitting the whole dataset in training and validation sets. The parameters of the method are computed by minimizing a loss function on the training set, and the hyper-parameters are then set by minimizing the loss function on the validation set. This approach is a bi-level optimization problem.
Other instances of such problems can be found in dictionary learning, robust training of neural networks or the use of implicit layers in deep learning. In all these applications, the model or the latent variables are learned by minimizing some loss while the parameters or the dictionary are updated by minimizing a second optimization problem depending on the outcome of the first problem. While theoretical results were produced in the early 70's 111, there are still many challenges related to bi-level optimization that need to be addressed to produce methods that are both theoretically well grounded and computationally efficient. Recently, the members of Mind have published several works related to the subject 79, 80, 92, 104. We intend to pursue this effort in the following directions.
Stochastic bi-level solvers.
Bi-level solvers require the use of the whole training set before doing an update on an outer-level problem: In this sense, they are full-batch methods 92. We propose to study stochastic methods for this task, where some improvement on the optimization can be achieved using only a few samples from the training data. Stochastic algorithms are notoriously faster than full-batch methods for large datasets, but are also generally harder to analyse from a theoretical standpoint. In addition to being fast, the proposed algorithm should come with some statistical guarantees. These solvers can have many applications, from stochastic prior learning for inverse problem to hyper-parameters tuning in general machine learning.
Neural Dictionary Learning.
Bi-level optimization framework offers a canvas to advance the state of the art in dictionary and prior learning. Indeed, dictionary learning has long been seen as a bi-level optimization problem 147. Practical algorithms are mainly based on alternate minimization and rarely account for the sub-optimality of each sub-problem. With advances in bi-level optimization and algorithm unrolling 79, we aim at providing efficient and theoretically justified dictionary learning algorithms, that will be able to leverage the technologies of differentiable programming 77, 165.
Deep Equilibrium Models.
The use of Deep learning, and in particular unrolled algorithms 126, has introduced a quantum leap in the resolution of inverse problems compared to variational approaches, specifically in terms of computing efficiency and image/signal recovery performance. However, these networks are very demanding in memory for the training, which currently limits their potential. Different methods exist to alleviate this problem both on the modeling (gradient check-pointing, reversible networks) and the implementation side (model parallelism, mixed precision), but come at the expense of larger computational cost. However, a promising research avenue, illustrated by 123, is the use of Deep Equilibrium Models. These models are defined implicitly and amount to unrolling an infinite number of iterations, thereby using much less memory. These implicit layers constitute another instance of bi-level optimization problem and we plan to work on these directions in the near future as a means to address DL image reconstruction in realistic 3D and 4D multi-coil MRI setting, both for structural and functional imaging.
3.1.3 Reinforcement learning for active k-space sampling
| Expected breakthrough: New hardware compliant under-sampling patterns in MRI k-space that accelerate anatomical and functional scans while optimizing MR image quality. |
| Findings: Develop novel principles of active sampling in the reinforcement learning framework which optimizes a sampling policy tightly linked to the reconstructed image quality. |
Current under-sampling schemes in MRI allow for shorter scan acquisition times, however at the cost of artifacts in various regions of the reconstructed MR image. These artifacts arise due to uncertainties in some heavily under-sampled regions of the acquired Fourier space (i.e. also called k-space). Modern reconstruction algorithms, with the use of strong priors, either hand-crafted or learned, tend to reduce these uncertainties and behave as if the acquisition is fixed.
To go beyond the state of the art, we argue that there is a need to jointly learn an algorithm that designs the optimal under-sampling pattern in k-space as well as the reconstruction network.
As it can be summarized to learning a sequential decision algorithm, we will rely on reinforcement learning (RL) to build up optimal k-space sampling patterns while enforcing physical constraints on the MRI sequence, as originally proposed in 100, 95, 140.
The k-space acquisition can be modeled by a sampling policy and the rewards for the joint network are based on reconstructed image quality. Under this paradigm, after every fixed scan time, an instantaneous reconstruction can be obtained and the Fourier space uncertainty maps analysed in depth. Based on this, the scan can continue by actively sampling the k-space and enforcing denser samples in regions where uncertainty is larger. In this way, the learned k-space trajectories may become more patient and organ specific. Further, the trajectory can run and lead to instantaneous best results of reconstruction under a given variable scan time budget. These aspects define one of the core directions we will investigate to produce the next generation of state-of-the-art MR data sampling and image reconstruction algorithms. Recent contributions 185, 166 only approach the problem in the Cartesian framework and hence perform 1D variable density sampling along the phase encoding dimension. Given our expertise on non-Cartesian sampling in developing SPARKLING for both for 2D and 3D MR imaging 140, 141, 98, we plan to extend this framework to non-Cartesian acquisition setups while still remaining compatible with hardware constraints on the gradient system. The access to various MRI scanners at CEA/NeuroSpin is necessary and an added advantage to the success of the Mind team.
3.2 Heterogeneous Data & Knowledge Bases
Participants:
B. Thirion, D. Wassermann
Inferring the relationship between the physiological bases of the human brain and its cognitive functions requires articulating different datasets in terms of their semantics and representation. Examples of these are spatio-temporal brain images, tabular datasets, structured knowledge represented as ontologies, and probabilistic datasets. Developing a formalism that can integrate all these modalities requires constructing a framework able to represent and efficiently perform computations on high-dimensional datasets as well as to combine hybrid data representations in deterministic and probabilistic settings. We will take on two main angles to achieve this task: on one hand, the automated inference of cross-dataset features, or coordinated representations and on the other hand, the use of probabilistic logic for knowledge representation and inference. The probabilistic knowledge representation part is now well advanced with the Neurolang project. It is yet a long-term endeavor. The learning of coordinated representations is less advanced.
3.2.1 Learning coordinated representations
| Expected breakthrough: Process semantic information together with image data to bridge large-scale resources and knowledge bases |
| Findings: Set up a learning model that leverages heterogeneous data: Images, annotations, texts, and coordinate tables. |
Inference is the pathway that leads from data to knowledge. One crucial aspect is that in the context of neuroscience, data comes in different forms: Full texts, images and tables. Annotations may be full texts or simply tags associated with observed images. One challenge is thus to develop automated techniques that learn coordinated representations across such heterogeneous data sources.
This learning endeavor rests on several key machine learning techniques: Compression, embeddings, and multi-layer networks. Compression (sketching) consists in building a reduced representation of some input that leads from large sparse and complex representation to low-dimension ones, while minimizing some distortion criterion. Embedding techniques also create representations, but possibly bias them to enhance some aspects of the data. It thus incorporates prior information on data distribution or the relevance of features. Finally, multi-layer networks create intermediate representation of data that are suitable to achieve a prediction goal. Such representations are rich enough in particular in multi-task settings, where the outputs of the network are multi-dimensional. Following 86, we call such latent data models coordinated representations.
Deep learning is well suited to the goal of learning intermediate representations. As an example, we plan to develop a framework that coalesces in one deep learning formulation, the task of estimating brain structures, cognitive concepts, and their relationships.
Brain structures and cognitive concepts will appear as intermediate representations responsible for linking brain activity to observed behavior. However deep learning cannot be considered as a standard means to understand coordinated representations, due to the limited data available, their poor signal-to-noise ratio (SNR) and their heterogeneity. Deep learning needs instead to be adapted by injecting our expertise on statistical structure of the data (see e.g. 128, 151). Since the challenge is to train such models on limited and noisy data, we will extend our recent work 84 that has developed regularization schemes for deep-learning models: it relies on structured stochastic regularizations (a.k.a. structured dropout). Such approaches are efficient, powerful and can be used in wide settings. We will enhance them with more generic, cross-layer, grouping schemes. Additionally, we will develop two strategies: i) aggregation of predictors for variance reduction and stability of the model 128 and ii) data augmentation – i.e. learning to augment, based on unlabeled data – to improve the fit with limited data. For this we will consider plausible generative mechanisms.
3.2.2 Probabilistic Knowledge Representation
| Expected breakthrough: A domain-specific language (DSL) capable of articulating heterogeneous probabilistic data sources in neuroimaging is a way to relate physiology to cognition. |
| Findings: Self-optimizing probabilistic solvers for discrete and continuous hierarchical models able to scale for neuroimaging problems. |
Neuroscientific data used to infer the relationships between physiology of the human brain and its cognitive function goes well beyond text, image, and tables. Knowledge graphs representing human knowledge, and the ability to encode reasoning strategies in neuroscience are also key to effectively bridge current data-centric approaches and decades-old domain knowledge. A main challenge in performing inferences combining demographic data-centric approaches, imaging measurements, and domain knowledge, is to be able to infer new knowledge soundly and efficiently taking into account the noisy nature of demographic and imaging measurements, and the common open-world assumption of ontologies and knowledge graphs. Such probabilistic hybrid logic approaches are known to be, in general, intractable in the deterministic 82 as well as in the probabilistic case 182. Nonetheless, there is an opportunity to be seized in identifying tractable segments of probabilistic hybrid logic representations able to solve open neuroscientific questions.
A noticeable opportunity to incorporate all statistical evidence gathered from noisy data into a usable knowledge base is to formalize the inferred relationships into probabilistic symbolic representations 129. These representations are much better suited to simultaneously handle data across topologies and logic systems, implementing inferential algorithms avoiding the brittleness of deterministic logic as well as causal probabilistic reasoning.
A typical application of such heterogeneous data processing is meta-analytic applications which combine neuroimaging data with results found in the scientific literature. Current tools to perform this task are NeuroSynth or Neuroquery (developed by the team). However, knowledge inferred by such tools is tremendously limited by the expressive power of the language used to query the data. Current meta-analytic tools are able to express queries relating test makers, article annotations, and their relationship with reported brain activations, support propositional logic only. Propositional logic requires the user to explicitly express every desired term with their characteristics and their relationships. Our goal is to extend the inference capabilities of such applications by leveraging current advances in probabilistic logic languages and embedding them in the Neurolang language. Neurolang enables the encoding of complex knowledge in terms of more expressive queries. Neurolang queries first-order logic segment, FO, with a tractable probabilistic extension allowing for high-dimensional and large dataset computations. Such segment of first order logic enables formalising questions such as “what brain areas are most likely reported active in a study specifically when terms related to consciousness are mentioned in such study”, hence being able to infer, amongst other tasks, specificity and causality 183 of diverse neuroscience phenomena. To disseminate our results allowing complex expressive searches of massively aggregated diverse data, we will leverage Neurolang. The latter produces a domain-specific language (DSL) for human neuroscience research, while being able to combine imaging data, anatomical descriptions and ontologies. Three main characteristics of the DSL are key to fulfilling this goal: First, it represents neuroimaging-derived information and spatial relationships in a syntax close to natural language used by neuroscientists 184. Second, through a back-end belonging to the Datalog family, it allows querying ontologies with the same expressive power as current standards SPARQL and OWL 88. Finally, we will extend Neurolang to a probabilistic language able to express graphical models allowing the implementation of a wide variety of causal inference and machine learning algorithms 85 in high-dimensional settings which are specific to neuroimaging research. In sum, by leveraging recent advances in deductive database systems 88 and this novel DSL 184 we will provide a more flexible tool to express and infer knowledge on brain structure-function relationships.
3.3 Statistics and causal inference in high dimension
Participants:
A. Gramfort, T. Moreau, B. Thirion, D. Wassermann
Statistics is the natural pathway from data to knowledge. Using statistics on brain imaging data involves dealing with high-dimensional data that can induce intensive computation and low statistical power. Besides, statistical models on large-scale data also need to take potential confounding effects and heterogeneity into account. To address these questions the Mind team will employ causal modeling and post-selection inference. Conditional and post-hoc inference are rather short-term perspectives, while the potential of causal inference stands as a longer-term endeavor.
3.3.1 Conditional inference in high dimension
| Expected breakthrough: Obtain statistical guarantees on the parameters of very-high dimensional generalized linear or non-parametric models. |
| Findings: Develop computationally efficient procedures that allow inference for such models, by leveraging structural priors on the solutions. |
Conditional inference consists of assessing the importance of a certain feature in a predictive model, while taking into account the information carried by alternative features. One motivation for using this inference scheme is that brain regions that sustain behavior and cognition are strongly interacting. Taking these interactions into account is critical to avoid confusing correlation with causation in brain/behavior analysis.
Technical difficulties come when the set of explanatory features becomes extremely large as frequently met in neuroimaging: Conditioning on many variables (or equivalently, high dimensional variables) is computationally costly and statistically inefficient. The main solutions to date are based either on linear model debiasing 134, as well as simulation-based approaches (knockoff inference 96 or conditional randomization tests 144). Importantly the latter involves simulating data with statistical characteristics described explicitly (in a parametric family) or implicitly (by samples). There remain two gaps to bridge for these methods: i) The computational gap, as the algorithmic complexity of these approaches is typically cubic in the number of samples, unless more efficient generative mechanisms are available; ii) the power gap, related to the limited number of available samples. The best solution thus far consists of associating these inference procedures with dimension reduction procedures 157. The next step is adaptation to more general settings: Conditional inference has been formulated in the linear framework, where it boils down to controlling that the corresponding coefficient is non-zero, hence it has to be generalized to nonlinear models: Non-parametric models like random forests, then possibly deep networks.
3.3.2 Post-selection inference on image data
| Expected breakthrough: Statistical control of false discovery proportion (FDP) for data under arbitrary correlation structure. |
| Findings: A computationally efficient non-parametric statistical test procedure, and a benchmark against alternative techniques. |
Large-scale statistical testing is pervasive in many scientific fields, where high-dimensional datasets are collected and compared with an outcome of interest. In such high-dimensional contexts, false discovery rate (FDR) control 90 is attractive because it yields reasonable power, while providing an explicit and interpretable control on false positives. Yet the FDR rate is the expectation of the FDP. Controlling the FDR does not mean that the FDP is controlled, a distinction that is most often ignored by practitioners. For the sake of scientific reproducibility, there is a need for methods controlling the FDP.
Such an approach has been developed in the context of neuroimaging, namely the all-resolution inference framework 173 based on classical multiple correction error control bounds. Yet, the empirical behavior of this method remains to be assessed. Moreover, it has been clearly established that the procedure is over-conservative in some settings 93. Indeed, it relies on the Simes statistical bound, that is not adaptive to the specific type of dependence for a particular data set. To bypass these limitations, 93 have proposed a randomization-based procedure known as -calibration, which yields tighter mathematical bounds that are adapted to the dependency observed in the dataset at hand. It rests on a non-parametric (permutation-based) estimation of the null distribution, leading to tight and valid inference under general assumptions.
In this research axis, we propose to fix some of the open issues with the approach described in 93, namely the choice of a template family to calibrate the error distribution in the permutation procedure. We hope to propose a practical choice for this family to avoid putting the burden of choice on practitioners.
We will characterize by simulations and theoretical arguments the behavior of these error control procedures and develop efficient computational methods for the use of these tools in brain imaging analysis.
3.3.3 Causal inference for population analysis
| Expected breakthrough: Provide a reference methodology for causal and mediation analysis in high-dimensional settings. |
| Findings: Benchmark state-of-the-art techniques and further adapt them to the high-dimensional setting. |
Modern health datasets present population characteristics with many variables and in multiple modalities. They can ground prediction and understanding of individual outcomes, using machine learning techniques. Still, heterogeneous variables have complex relationships, making it hard to tease apart each factor in an outcome of interest. Potential outcome theory 175 provides a valuable framework to evaluate the impact of treatment (interventions). Treatment effects can be heterogeneous. In particular, interactions between background and treatment variables have to be considered.
The statistical behavior (consistency and efficiency) under non-parametric models is actively investigated 83, 159. However, their behavior in high-dimensional settings, when both the number of features and the number of samples are large, is still poorly understood. Our objective is thus to extend the theory and algorithms of causal inference to noisy high-dimensional settings, where the noise level implies that effects sizes are proportionally small, and classic methods often become inefficient and potentially inaccurate due to overfitting. More specifically, we plan to explore the following directions.
Mediation analysis and conditional independence
Mediation analysis considers the question of whether a variable mediates all the effect of another variable onto a target variable , a.k.a. outcome. It turns out that full-mediation analysis amounts to testing whether ( is independent from given ), which is handled by a conditional independence test. When the dimensions of these variables ( in particular, but also and to some extent ) grow, the underlying statistical inference procedures typically lose power, or even possibly error control. We propose to leverage our experience on such high-dimensional inference problems 105, 158 to set up computationally efficient and accurate solutions to this problem.
Latent variable models and confounders
The most important aspect of inferring causal effects from observational data is the handling of confounders, i.e., factors that affect both an intervention and its outcome. For instance, age has a clear impact on brain characteristics as well as on behavior, potentially biasing brain/behavior statistical associations. A carefully designed observational study attempts to measure all important confounders. When one does not have direct access to all confounders, there may exist noisy and uncertain measurements of proxies for confounders. A possible solution to this problem relies on generative modeling, such as Variational Autencoders (VAE) and Generative Adversarial Networks (GANs), to sample the unknown latent space summarizing the confounders on datasets with incomplete information; the seminal work of 146 is promising, but still requires improvements to become usable in realistic settings.
The quest of model selection and validation
In the classical potential outcome theory 175, causal effects are determined by both factual and counterfactual outcomes, ground-truth effects can never be measured in an observational study. In the absence of such measures, how can we evaluate the performance of causal inference methods? Addressing this question is an important step for practical problems, in which one has to determine if an effect can safely be considered non-zero, or heterogeneous through a population. We propose to revisit the promising work of 81 analysing in detail the shortcomings of the procedure (regarding both bias and variance), especially when the model becomes high-dimensional.
3.4 Machine Learning on spatio-temporal signals
Participants:
P. Ciuciu, A. Gramfort, T. Moreau, D. Wassermann, B.Thirion
The brain is a dynamic system. A core task in neuroscience is to extract the temporal structures in the recorded signals as a means to linking them to cognitive processes or to specific neurological conditions. This calls for machine learning methods that are designed to handle multivariate signals, possibly mapped to some spatial coordinate system (e.g. like in fMRI).
3.4.1 Injecting structural priors with Physics-informed data augmentation
| Expected breakthrough: Obtain models with more predictive power when trained on small datasets. |
| Findings: Efficient data-augmentation strategy tailored to brain signals. |
Data augmentation consists of virtually increasing dataset size during learning by applying random, yet plausible, transformations to the input data. In computer vision, this means altering data by applying symmetries, rotations, geometric deformations etc. While such strategies are reasonable for natural or medical images 164, it is still unclear how neural or BOLD signals can be augmented in order to improve prediction performance and robustness.
Some purely data driven strategies have been proposed to augment EEG data using spectral transforms 145 or advanced strategies such as channel, time or frequency masking or phase randomizations 139, 142. Although dozens of transformations have been considered in the literature to augment EEG signals, it is now apparent that different augmentation strategies should be applied to the data as a function of the prediction task to be handled. For example when considering sleep stage classification or BCI applications, the spatial sampling of electrodes and the duration of signals varies considerably, with the consequence being that different augmentation parameters and even transformations need to be employed.
In this line of work we will develop algorithms that can quickly identify the relevant augmentation techniques, building for example on 108, 144. The aim is to provide a system that can automatically learn invariance within a class and across subjects in order to maximize the prediction performance on unseen data. The methodology developed will be relevant beyond neuroscience as long as a family of physics-informed transformations is available for prediction tasks at hand.
3.4.2 Learning structural priors with self-supervised learning
| Expected breakthrough: Unveiling the latent structure of brain signals from large datasets without human supervision as well as improving the prediction performance when learning from limited data. |
| Findings: Self-supervised algorithms for multivariate brain signals. |
Self-supervised learning (SSL) is a recently developed area of research that provides a compelling approach for exploiting large unlabeled datasets. With SSL, the structure of the data is used to turn an unsupervised learning problem into a supervised one, called a “pretext task”, such as solving Jigsaw puzzles from images 161 or learning how to color gray-scaled images. The representation learned on the pretext task can then be reused for unsupervised data exploration or on a supervised downstream task, with the potential to greatly reduce the number of labeled examples required to train a good predictive model.
In fields like computer vision 161, 153 and time series processing 162, SSL has shown great promise in terms of prediction performance but also in ease of use. Indeed, SSL simplifies model selection and evaluation as it relies on prediction scores and cross-validation, contrarily to unsupervised learning methods like ICA 78.
Recently the team has applied SSL to two large cohorts of clinical EEG data 87 revealing insights on the data without any human supervision. However many challenges remain. For example in Mind, we aim to explore novel SSL strategies applicable to electrophysiology as well as to haemodynamic signals measured with fMRI. As such, our goal is to expand the recent multivariate method we have introduced in the field for the blind deconvolution of BOLD signals in both task-related and resting-state experiments 103.
While rather small networks have been employed so far on EEG data 99, 174 due to limited sets of annotations, the use of SSL tasks opens the possibility to work with much larger labeled datasets, and therefore many more overparametrized models. We aim to explore these directions, hoping to reach a state where pre-trained models could be available for EEG or MEG signals as is presently the case for images or for natural language processing (NLP) tasks.
3.4.3 Revealing spatio-temporal structures with convolutional sparse coding and driven point processes
| Expected breakthrough: A novel way to study and quantify temporal dependencies between neural processes, going beyond connectomes based on spectral analysis. |
| Findings: Temporal pattern finding algorithms that scale to massive MEG/EEG datasets with parallel processing and point-process inference algorithms. |
The convolutional sparse linear model is one established unsupervised learning framework designed for signals. Using algorithms known as convolutional sparse coding (CSC), this framework allows for the learning of shift-invariant patterns to sparsely reconstruct a time series. These patterns, also called atoms, correspond to recurrent structures present in the data. While some of our recent advances have improved the computational tractability of these methods 155, 154 and adapted them to neurophysiological data 133, 117, 103, there are still many shortcomings that make them unpractical for applications beyond denoising.
Model validation
The main challenge for the evaluation of unsupervised convolutional models comes from current theoretical limitations: What can we guarantee statistically concerning the recovered atoms? Due to their non-convexity, existing algorithms can only guarantee convergence to local minima, which might be sub-optimal. In this setting, it is challenging to quantify if the model parameters are well estimated and if they are actually representative of the signals. In Mind, we aim to develop statistical quantification of the uncertainty associated with such models and in this regard, provide objective selection criteria for the model and its parameters. This topic of research will benefit from our other developments on bi-level optimization (cf. ssub:bilevel) and on FDR control (cf. ssub:postselection) as well as the expertise of the team members on dictionary learning 155, 152, 154.
Capturing temporal dependencies with point processes
Another shortcoming of these models is that they do not capture temporal dependencies between the occurrences of the different atoms. However, neural activity at level of the whole brain is highly distributed. Different brain regions form networks that are characterized by the presence of statistical dependencies in their activity 163. An interesting question to formulate is how one can model and learn these time dependencies between brain areas from the MEG or EEG recordings using an unsupervised event-based approach such as CSC. One of the approaches considered is based on point processes (PP; 94, 127). PP are classical tools to study event trains (e.g. sequence of spikes) and to model their dependency structure. We aim here to develop PP-based inference algorithms as a means to capture network effects in different brain areas, but also to quantify how experimental stimuli are affecting the temporal statistics of temporal patterns 163. To model this latter scenario, we will develop the so-called driven PP. In a second stage, we aim to design fully unsupervised methods to capture the connections between different brain areas leveraging the full temporal resolution of non-invasive electrophysiological signals.
4 Application domains
The four research axes we presented earlier have been thought of in tight interaction with four main applications (large-scale predictive modeling, mapping cognition & brain networks, modeling clinical endpoints, from brain images and bio-signals to quantitative biology and physics).
4.1 Population modeling, large-scale predictive modeling
4.1.1 Unveiling Cognition Through Population Modeling
Linking the human brain's structure and function with cognitive abilities has been a research epicenter for the past 40 years. The sophistication of brain mapping machinery such as MRI, EEG and MEG, has produced a treasure trove of data. Nonetheless, the effect size of the phenomena leading to understanding cognition is often drowned out by noise and inter-individual variability. A main goal of Mind is to simultaneously harness the power of large-scale general purpose datasets, such as the Human Connectome Project (HCP) and the Adolescent Brain Cognitive Development Study (ABCD), as well as small scale high precision ones, such as the Individual Brain Charting (IBC) dataset 168, to understand the link between the human brain's architecture and function, and cognition. Parietal's expertise has already been demonstrated in this field. Examples of this include using diffusion MRI (dMRI) to link the brain's macrostructure with language comprehension 101, tissue microstructure with cognitive control 150, functional gradients on the cortical surface 115 to functional territory segregation 167.
Mind project will continue this task by seizing our core methodological developments, described in the previous section, and our global collaborative network of cognitive scientists.
4.1.2 Imaging for health in the general population
Individual differences in brain function and cognition have historically been investigated by studies carried out by individual laboratories having access mainly to small sample sizes. The growing availability of public large-scale data of epidemiological dimensions curated by dedicated consortia (e.g. UK Biobank) has enabled studying the relationship between cognition and the brain with unparalleled granularity and statistical power. These resources now allow researchers to relate brain signals/images to rich descriptions of the participants including behavioral and clinical assessments in addition to social and lifestyle factors. Machine learning has proven essential when modeling biomedical outcomes from the large-scale and high-dimensional data brought by consortia and biobanks. It is used to to build predictive models of heterogenous biomedial outcomes (cognitive, social, clinical) based on different neuroscientific modalities. Taken together, this facilitates the study of lifestyle and health-related behavior in the general population, potentially revealing risk factors leading to biomarker discovery.
Mind will greatly contribute to this effort by focusing on population modeling as a tool for enhancing the analysis of clinical data and mental health.
4.1.3 Proxy measures of brain health
Clinical datasets tend to be small as sharing of data is not incentivized or institutional and economic resources are missing. As a consequence, the capacity of machine learning to learn functions that relate complex-to-grasp biomedical outcomes to heterogeneous data cannot be fully exploited. This has stimulated growing interest in proxy measures of neurological conditions derived from the general population, such as individual biological aging. One counter-intuitive aspect of the methodology is that measures of biological aging (e.g. via brain imaging) can be obtained by focusing on the age of a person, which is known in advance and is, in itself not interesting as a target. However, by predicting the age, machine-learning can capture the relevant information about aging. Based on a population of brain images, it extracts the best guess for the age of a person, indirectly positioning that person within the population. Individual-specific prediction errors therefore reflect deviations from what is statistically expected 181. The brain of a person can look similar to brains commonly seen in older (or younger) people. The resulting brain-predicted age reflects physical and cognitive impairment in adults 180, 106, 116 and reveals neurodegenerative processes 143, 124, which could be overlooked without using machine learning.
Mind will extend this line of research in two directions: 1) Assessment of brain age using EEG and non-brain data such as health-records and 2) proxy measures of mental health beyond aging.
4.1.4 Studying brain age using electrophysiology
MRI is not yet available in all clinical situations and certain aspects of brain function are better understood using electrophysiological modalities (M/EEG). Until recently, it was unclear if brain age can be meaningfully estimated from M/EEG. In a recent study 121, we demonstrated, using the Cam-CAN cohort (), that combining MRI and MEG enhanced detection of cognitive dysfunction. The proposed approach not only achieved integration of brain signals from distinct modalities but explicitly handled the absence of MEG or MRI recordings, adapting ideas from 136. This is key for clinical translation where one cannot afford excluding cases because one modality is missing. In the clinical setting, EEG is predominantly used (and not MEG). Clinical recordings are far noisier than lab EEG and gold-standard source modeling with MRI is rarely done outside the lab. Supported by theoretical analysis and simulations, we found through empirical benchmarks 176 that Riemannian embeddings 1) capture individual head geometry 2) bring robustness to extreme noise and, 3) enable good age prediction from clinical 20-channel EEG (n=1300) with performance close to 306-channel lab MEG.
Mind will extend this line of research by translating EEG-based brain age measures into the hospital setting and probe these in different patient populations in which ageing-related differences in brain structure and function are part of the clinical picture, e.g., neurodevelopmental disorders, postoperative cognitive decline and dementia (cf. MIND:subsec:MCE).
4.1.5 Proxy measures of mental health beyond brain aging
Quantitative measures of mental health remain challenging despite substantial research efforts 137. Mental health, can only be probed indirectly through psychological constructs, e.g. intelligence or anxiety gauged by valid and statistically relevant questionnaires or structured examinations by a specialist. In practice, full neuropsychological evaluation is not an automated process but relies on expert judgment to confront multiple responses and interpret them in the context of a larger environmental context including the cultural background of the participant. Inspired by brain age, we set out to build empirical measures of mental health 109 by predicting traditional and broadly used psychological constructs such as fluid intelligence or neuroticism in the UK Biobank. Our results have shown that all proxies captured the target constructs and were more useful than the original measures for characterizing real-world health behavior (sleep, exercise, tobacco, alcohol consumption). In the long run, we anticipate that using proxies could complement psychometric assessments by corroborating data and potentially providing more accurate data faster and more efficiently for clinical populations.
Mind will expand this line of research by systematically searching for proxy measures of physical and mental health derived from large clinical population using electronic health records or transcripts from clinical interviews. We will propose a systematic causal analysis (treatment effect size and mediation) to provide a clearer understanding of the relationships between the many variables that characterize mental health. We will study more in detail the impact of general health markers on brain status, as this may well fit much of the unexplained variance on brain health.
4.2 Mapping cognition & brain networks
4.2.1 Problem statement
Cognitive science and psychiatry aim at describing mental operations: cognition, emotion, perception and their dysfunction. As an investigation device, they use functional brain imaging, that provides a unique window to bridge these mental concepts to the brain, neural firing and wiring. Yet aggregating results from experiments probing brain activity into a consistent description faces the roadblock that cognitive concepts and brain pathologies are ill-defined. Separation between them is often blurry. In addition, these concepts (a.k.a. psychological constructs) may not correspond to actual brain structures or systems. To tackle this challenge, we propose to leverage rapidly increasing data sources: text and brain locations described in neuroscientific publications, brain images and their annotations taken from public data repositories, and several reference datasets.
4.2.2 What machine learning can do for neuroscience
Recent works in computer vision 113 or natural language processing 107, 114 have tackled predictions on a large number of classes, getting closer to open-ended knowledge. These approaches, that rely on uncovering some form of relational structure across these classes, in effect capture the semantics of the domain 107, including the similarity structure of the relevant classes and the ambiguities across classes or the multiple aspects of a class. Broadly speaking, these contributions converge to the concept of representation learning 89, i.e. estimating latent factors that reformulate a learning problem into a new set of input features or output classes that are more natural for the data and help further analysis. These new tools enable extraction of knowledge, for instance ontology induction, with statistical learning 160. They are at the root of heterogeneous data integration, such as multi-modal machine learning 86. The machine learning challenges that we aim to tackle are three-fold:
- Existing multi-modal machine learning techniques have been developed for relatively abundant data, with overall high SNR: text, natural images, videos, sound. These data are most often non-ambiguous, while brain data typically are, due to the low SNR per image and, more crucially, poor annotation quality. We propose to tackle this by adapting machine learning solutions to this low-SNR regime: introduction of priors, aggressive dimension reduction, aggregation approaches and data augmentation to reduce overfitting.
- Leveraging implicit supervisory signals: While data sources contain lots of implicit information that could be used as targets in supervised learning, there is most often no obvious way to extract it. We propose to tackle this by using additional, ill- or not-annotated data, relying on self-supervision methods.
- Model interpretability: Our goal is to provide clear assertions on the relationships between brain structures and cognition: the inference should always lead to an updated knowledge base, i.e. updated relationships between concepts pertaining to neuroscience on one hand, psychology on the other hand. Specifically, one should be able to reason about the information extracted within Mind. For this, we will develop dedicated statistical, causal and formal (ontology-based) data analysis schemes.
Associating knowledge engineering with statistical learning to boost cognitive neuroimaging, requires tackling the challenge of multimodal machine learning under noisy conditions with limited data. Doing so, it will capture links between behavior and brain activity, and enable aggregating the information carried by neuroimaging data to redefine and link concepts in psychology and psychiatry.
4.2.3 Perspective taken: combine distributional semantics with brain images
In natural language processing (NLP), distributional semantics capture meanings of words using similarities in the way they appear in their environment. We want to adapt these ideas to learn data-driven organizations of psychological concepts. Importantly, applying these techniques solely to the psychology literature merely captures the current status quo of the field. Including brain images is necessary to bring new information.
To link observed cognition to brain activity, two typical statistical learning problems arise: encoding, that seeks to describe brain activity from behavior; and decoding, that seeks the converse, predicting behavior from brain activity 138. In addition, statistical modeling of each aspect of the data on its own generates knowledge, typically spatial decompositions from resting-state data, and topic modeling on descriptions of behavior. The research strategy followed in this proposal is to combine the different statistical learning problems in a unified framework to extract core structures from the aggregation of neuroimaging data: on one side brain structures, and on the other side semantic relationships and concepts in psychological sciences.
Mind will in particular publish automated functional meta-analyses to give a systematic assessment of the publicly available data and question the limitations of the current conceptual framework of systems neuroscience as well as of these resources.
4.3 Modeling clinical endpoints
When sufficient data is available, machine learning can be employed to directly model various clinical endpoints (such as diagnosis, drug response, and neuropsychological scores) from brain signals without the need for proxy measures. This approach has the potential to significantly and meaningfully simplify statistical modeling in clinical research. Machine learning facilitates combining heterogeneous input data (different modalities) and does not need high confidence in underlying generative models linking the data to the clinical endpoint. As a consequence, the same class of models can be applied regardless of the endpoint. Its focus is on bounding the approximation error of the endpoint instead of correct parameter estimates. As such, it provides generalizing models that are more robust. Our team has pushed this type of research program through several important collaborations with our European clinical partners using EEG and MRI.
4.3.1 MRI-based modeling of clinical endpoints
Image based biomarkers can be objectively measured and are a sign of normal or abnormal processes, of a condition or disease. Incorporating new potential imaging biomarkers requires several steps, often in parallel and complementary to each other, to be undertaken for translation into clinical practice. These can be divided into the following phases after identification: Development and evaluation, validation, implementation, qualification, and utilization. Our team aims to cross two main translational gaps, that is, the translation from patients first and then to practice. Our aim through our current and active projects is to ensure that potential biomarkers, like the clear delineation of subterritories of the subthalamic nucleus (STN) in pharmaco-resistant Parkinson's disease (PD) patients (i.e.candidates for implantation of a deep brain stimulator) are `fit for purpose' and associated with the clinical endpoint of interest with the overarching goal being to demonstrated efficacy and health impact. This process is key to the translation into clinical practice and widespread utilization.
Through the ANR VLFMRI grant we aim to derive new MR imaging-based biomarkers related to prematurity and abnormal neurodevelopment of hospitalized neonates at low magnetic field (20 mTesla). In this setup, the objective is to perform an almost continuous monitoring to detect early signs of adverse events including ischemic stroke or encephalopathy (collaboration with Prof. V. Biran, APHP Robert Debré Hospital). An additional collaboration is already underway with the AP-HP Henri Mondor Hospital (neuroradiologist Dr B. Bapst, doing part of her PhD at NeuroSpin), to achieve high-resolution susceptibility weighted imaging (600 µisotropic) in a scan time of 2m30s for an accurate delineation of the STN in PD patients prior to surgical planning. A database of 123 patients has already been collected using both the standard SWI imaging protocol and ours based on the SPARKLING technology. This annotated database will be key to compare the diagnosis power of our solution with that of the current care, analyse to what extent a higher image resolution is instrumental in providing a more accurate clinical diagnostic, and finally make our protocol more widely accepted in the clinical practice.
Our key contribution in these projects is to translate to the clinical realm both the SPARKLING technology on the acquisition side 141, 98 as well as our PySAP software 122 for MR image reconstruction. In this regard, the recently accepted CEA postdoc funding should help us move the technology to clinical 7T MR Systems (Magnetom Terra Siemens-Healthineers) in the University hospital of Poitiers through a nascent collaboration with Prof. Rémy Guillevin. Their interest is to use the high-resolution SPARKLING SWI protocol at 7T to better delineate the anomalies along the central vein for the diagnostic of multiple sclerosis as the number of anomalies predicts the grade/severity of this inflammatory pathology. On a longer perspective, we aim to generalize the use of our recently DL networks for MR image reconstruction 171, 169 to multiple acquisition setups and other downstream tasks (e.g. motion correction and correction of off-resonance artifacts related to inhomogeneities).
4.4 From brain images and bio-signals to quantitative biology and physics
Thanks to the developments in MIND:subsec:MLIP and MIND:subsec:MLSTP we aim to approximate more accurately the biophysical models underlying MRI and electrophysiological signals. By estimating quantities grounded in the physics of the data (time, spatial localization, tissue properties) we ambition to offer more actionable outputs for cognitive, clinical and pharmacological applications.
Technologies like 4D SPARKLING should in the future allow us to carry out both fast high resolution multi-parametric quantitative imaging (e.g. T1, T2 and proton density mapping) and laminar (i.e. layer-based) functional imaging in BOLD-fMRI. First, in the mqMRI and fMRI setting, the fourth dimension is respectively the weighting contrast and time axis. mqMRI imaging enables a precise quantification of biomarkers such as iron stores in the pathological brain. Measuring these parameters intra-cortically in Parkinsonian patients defines one of the key challenges in the coming years, especially at 7 Tesla, to earlier stratify the PD patients and the evolution of their disease. Second, a particular attention will be paid to the impact of the developments performed in MIND:subsec:MLIP on the statistical sensitivity of brain activity detection, which eventually defines the final validation metric of the data acquisition/image reconstruction pipeline. For this purpose, robust experimental activation protocols such as retinotopic mapping will be used for validation on the 7T scanner and eventually on the 11.7T Iseult MR system. The finest target resolution is 500 isotropic in 3D.
Novel development on bi-level optimization for hyper-parameter selection from ssub:bilevel will bring state-of-the-art inverse methods to end users currently facing the difficulty of performing model selection on empirical data efficiently. This will lead to more accurate quantitative assessments, in sub-millimeters and milliseconds, of where neural activity occurs.
The line of work on inverse problems should also impact how non-invasive neuroimaging and electrophysiology, based on MRI, EEG and MEG, is considered by more traditional neurophysiologists working with animal data. By considering biophysical models of the data and aiming to estimate their parameters from empirical recordings our hope is to present estimates of physical quantities (tissue properties, neural interactions strengths, etc.). The line of work based on stochastic simulation based inference (SBI) can revolutionize the way MEG, EEG and MRI data are apprehended. For this line of work we will explore the inversion of the models as offered by major software such as The Virtal Brain (TVB) 177 or the Human Neocortical Neurosolver (HNN) 156. A student from the group of Prof. S. Jones at the origin of the HNN software visited the team in 2022.
5 Social and environmental responsibility
The MIND team has not yet implemented specific guidelines for measuring carbon emission related to its research activities. Team members maximize the use of train for travelling across Europe and try to minimize the number of oversea flights per individual. The team also has a preference for lightweight computation when possible.
6 Latest software developments, platforms, open data
6.1 Latest software developments
6.1.1 MNE
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Name:
MNE-Python
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Keywords:
Neurosciences, EEG, MEG, Signal processing, Machine learning
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Functional Description:
Open-source Python software for exploring, visualizing, and analyzing human neurophysiological data: MEG, EEG, sEEG, ECoG, and more.
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Release Contributions:
https://mne.tools/stable/whats_new.html
- URL:
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Contact:
Alexandre Gramfort
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Partners:
HARVARD Medical School, New York University, University of Washington, CEA, Aalto university, Telecom Paris, Boston University, UC Berkeley, Macquarie University, University of Oregon, Aarhus University
6.1.2 NeuroLang
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Name:
NeuroLang
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Keywords:
Neurosciences, Probabilistic Programming, Logic programming
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Functional Description:
NeuroLang is a probabilistic logic programming system specialised in the analysis of neuroimaging data, but not exclusively determined by it.
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Release Contributions:
https://neurolang.github.io/
- URL:
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Contact:
Demian Wassermann
6.1.3 Nilearn
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Name:
NeuroImaging with scikit learn
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Keywords:
Health, Neuroimaging, Medical imaging
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Functional Description:
NiLearn is the neuroimaging library that adapts the concepts and tools of scikit-learn to neuroimaging problems. As a pure Python library, it depends on scikit-learn and nibabel, the main Python library for neuroimaging I/O. It is an open-source project, available under BSD license. The two key components of NiLearn are i) the analysis of functional connectivity (spatial decompositions and covariance learning) and ii) the most common tools for multivariate pattern analysis. A great deal of efforts has been put on the efficiency of the procedures both in terms of memory cost and computation time.
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Release Contributions:
HIGHLIGHTS - Updated docs with a new theme using furo. - permuted_ols and non_parametric_inference now support TFCE statistic. - permuted_ols and non_parametric_inference now support cluster-level Family-wise error correction. - save_glm_to_bids has been added, which writes model outputs to disk according to BIDS convention.
NEW - save_glm_to_bids has been added, which writes model outputs to disk according to BIDS convention. - permuted_ols and non_parametric_inference now support TFCE statistic. - permuted_ols and non_parametric_inference now support cluster-level Family-wise error correction. - Updated docs with a new theme using furo.
See all details in https://nilearn.github.io/stable/changes/whats_new.html
- URL:
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Contact:
Bertrand Thirion
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Participants:
Pierre-Louis Barbarant, Remi Gau, Himanshu Aggarwal, Bertrand Thirion, Gael Varoquaux
6.1.4 Benchopt
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Keywords:
Benchmarking, Machine learning, Optimization
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Functional Description:
BenchOpt is a package to simplify, make more transparent and more reproducible the comparisons of optimization algorithms. It is written in Python but it is available with many programming languages. So far it has been tested with Python, R, Julia and compiled binaries written in C/C++ available via a terminal command. If it can be installed via conda, it should just work!
BenchOpt is used through a simple command line and ultimately running and replicating an optimization benchmark should be as easy a cloning a repo and launching the computation with a single command line. For now, BenchOpt features benchmarks for around 10 convex optimization problems and we are working on expanding this to feature more complex optimization problems. We are also developing a website to display the benchmark results easily.
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Release Contributions:
https://github.com/benchopt/benchopt/releases/tag/1.8.0
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News of the Year:
Building on the momentum of the 2024 sprint, Benchopt’s development in 2025 focused on maturing its infrastructure for large-scale machine learning and industrial-grade workflows. A key highlight was the "supercharging" of the parallel backend, particularly through the SLURM executor, which now supports solver-specific overrides (allowing, for instance, GPU allocation only for specific methods) and better management of parallel job limits. Machine learning support was significantly bolstered by the introduction of the collect command for gathering distributed results, improved serialization for complex parameter spaces, and the integration of high-profile benchmarks like NanoGPT and SLOPE. Furthermore, the framework moved toward a more robust ecosystem with the release of version 1.7.0, featuring enhanced HTML result pages with interactive tables, improved Windows compatibility, and the ability for objectives to produce multiple entries simultaneously—solidifying Benchopt as a comprehensive tool for both classical optimization and modern deep learning research.
- Publication:
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Contact:
Thomas Moreau
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Participants:
Thomas Moreau, Mathurin Massias, Hippolyte Verninas, Melvine Nargeot, Jad Yehya
6.1.5 Scikit-learn
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Keywords:
Clustering, Classification, Regression, Machine learning
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Scientific Description:
Scikit-learn is a Python module integrating classic machine learning algorithms in the tightly-knit scientific Python world. It aims to provide simple and efficient solutions to learning problems, accessible to everybody and reusable in various contexts: machine-learning as a versatile tool for science and engineering.
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Functional Description:
Scikit-learn can be used as a middleware for prediction tasks. For example, many web startups adapt Scikitlearn to predict buying behavior of users, provide product recommendations, detect trends or abusive behavior (fraud, spam). Scikit-learn is used to extract the structure of complex data (text, images) and classify such data with techniques relevant to the state of the art.
Easy to use, efficient and accessible to non datascience experts, Scikit-learn is an increasingly popular machine learning library in Python. In a data exploration step, the user can enter a few lines on an interactive (but non-graphical) interface and immediately sees the results of his request. Scikitlearn is a prediction engine . Scikit-learn is developed in open source, and available under the BSD license.
- URL:
- Publications:
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Contact:
Gael Varoquaux
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Participants:
Thomas Moreau, Jerome Dockes, Alexandre Gramfort, Bertrand Thirion, Gael Varoquaux, Loic Esteve, Olivier Grisel, Guillaume Lemaitre, Jeremie Du Boisberranger, Julien Jerphanion
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Partners:
Axa, BNP Parisbas Cardif, Dataiku, Nvidia, Chanel, Probabl
6.1.6 joblib
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Keywords:
Parallel computing, Cache
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Functional Description:
Facilitate parallel computing and caching in Python.
- URL:
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Contact:
Thomas Moreau
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Participants:
Thomas Moreau, Loic Esteve, Olivier Grisel, Gael Varoquaux, Yoann Coudert–Osmont
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Partner:
Probabl
6.1.7 MRI-NUFFT
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Keywords:
Brain MRI, NUFFT, Trajectory Generation
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Functional Description:
MRI-NUFFT is a python package that extends various NUFFT (Non-Uniform Fast Fourier Transform) python bindings used for MRI reconstruction. It provides a unified interface with a large number of backends with implementations ranging from CPU to GPU.
In particular, it provides a unified interface for all the methods, with extra features such as coil sensitivity, density compensated adjoint and off-resonance corrections (for static B0 inhomogeneities). Additionally, useful IO tools like reading a k-space sampling trajectory and writing a binary file for run on MR scanner is also offered. Finally, it helps algorithmically speed up MR image reconstruction algorithms through fast ways to estimate preconditioning weights, also known as density compensators for a given sampling pattern.
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Release Contributions:
MRI-NUFFT now provides a physical model of the MRI acquisition processes, including multi-coil acquisition and static-field inhomogeneities. This model is compatible with the NUFFT libraries, and can be used to simulate the acquisition of MRI data, or to reconstruct data from a given set of measurements. MRI-NUFFT comes with a wide variety of non-Cartesian trajectory generation routines that have been gathered from the literature. It also provides ways to extend existing trajectories and export them to specific formats, for use in other toolkits and on MRI hardware. Finally, MRI-NUFFT provides automatic differentiation for all NUFFT backends, with respect to both gradients and data (image or k-space). This enables efficient backpropagation through NUFFT operators and supports research on learned sampling model and image reconstruction network.
- URL:
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Contact:
Chaithya Giliyar Radhkrishna
6.1.8 SPARKLING
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Name:
Spreading Projection Algorithm for Rapid K-space sampLING
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Keywords:
Brain MRI, MRI, Optimization
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Scientific Description:
This python package allows us to generate "SPARKLING" curves as a new type of non-Cartesian trajectories to perform a more efficient sampling in 2D and 3D for anatomical imaging while using the same number of samples for a limited time budget. These segmented curves are obtained using a projection method on measure sets which offers three main advantages: i) generating segmented Non-Cartesian trajectories along a chosen density, ii) meeting the hardware constraints on the magnetic field gradients (magnitude, slew rate), iii) performing a fast coverage of k-space.
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Functional Description:
This python package implements "SPARKLING": an optimization driven method to obtain hardware compliant sampling curves that globally satisfy a user specified target sampling density. The resulting non-cartesian sampling curves can be used to efficiently undersample and speed up acquisitions on an MR scanner. This method is generic enough that it can be applied to any of the imaging modalities in MR.
- Publications:
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Contact:
Chaithya Giliyar Radhkrishna
6.1.9 PySAP
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Name:
Python Sparse data Analysis Package
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Keywords:
Image reconstruction, Image compression
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Functional Description:
The PySAP (Python Sparse data Analysis Package, https://github.com/CEA-COSMIC/pysap) open-source image processing software package has been developed for the 3 years between the Compressed Sensing group at Iniria-CEA Parietal team led by Philippe Ciuciu and the CosmoStat team (CEA/IRFU) led by Jean-Luc Statck. It has been developed for the COmpressed Sensing for Magnetic resonance Imaging and Cosmology (COSMIC) project. This package provides a set of flexible tools that can be applied to a variety of compressed sensing and image reconstruction problems in various research domains. In particular, PySAP offers fast wavelet transforms and a range of integrated optimisation algorithms. It also offers a variety of plugins for specific application domains: on top of Pysap-MRI and PySAP-astro plugins, several complementary modules are now in development for electron tomography and electron microscopy for CEA colleagues. In October 2019, PySAP has been released on PyPi (https://pypi.org/project/python-pySAP/, currently version 0.0.3) and in conda (https://anaconda.org/agrigis/python-pysap).
The Pysap-MRI has been advertised through a specific abstract accepted to the next workshop of ISMRM on Data Sampling & Image Reconstruction in late January 2020. It will be presented during a power pitch session together wih an hands-on demo session using JuPyter notebooks.
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Contact:
Philippe Ciuciu
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Partner:
CEA
6.1.10 SNAKE
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Name:
Simulator from neuro-activation to K-space Exploration
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Keywords:
FMRI, NUFFT
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Functional Description:
We propose a new, modular, open-source, Python-based 3D+time fMRI data simulation software, SNAKE-fMRI, which stands for Simulator from Neurovascular coupling to Acquisition of K-space data for Exploration of fMRI acquisition techniques. Unlike existing tools, the goal here is to simulate the complete chain of fMRI data acquisition, from the spatio-temporal design of evoked brain responses to various multi-coil k-space data 3D sampling strategies, with the possibility of extending the forward acquisition model to various noise and artifact sources while remaining memory-efficient. By using this in silico setup, we are thus able to provide realistic and reproducible ground truth for fMRI reconstruction methods in 3D accelerated acquisition settings and explore the influence of critical parameters, such as the acceleration factor and signal-to-noise ratio (SNR), on downstream tasks of image reconstruction and statistical analysis of evoked brain activity. We present three scenarios of increasing complexity to showcase the flexibility, versatility, and fidelity of SNAKE-fMRI: From a temporally-fixed full 3D Cartesian to various 3D non-Cartesian sampling patterns, we can compare — with reproducibility guarantees — how experimental paradigms, acquisition strategies and reconstruction methods contribute and interact together, affecting the downstream statistical analysis.
- URL:
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Contact:
Philippe Ciuciu
6.2 Open data
Participants: Main External Collaborators: Bertrand Thirion, Ana Fernanda Ponce, Himanshu Aggarwal, Ana-Luisa Pinho [Western University, Canada], Lucie Hertz-Pannier [CEA/NeuroSpin].
The MIND is an an open data provider as it produced the Individual Brain Charting (IBC) data set over the last year in the context of the Human Brain Project. The IBC data set consists of anatomical and functional brain MR images collected on twelve healthy volunteers. It is quite unique as approxilmately 50 to 60 different behaviarol protocols have been run on these individuals. The IBC data set can be uploaded here.
7 New results
7.1 SPARKLING for fMRI
Participants: Zaineb Amor, Philippe Ciuciu.
Main External Collaborators: Alexandre Vignaud [CEA/NeuroSpin].
Additionally, we have shown that 3D-SPARKLING is a viable imaging technique and good alternative to Echo Planar Imaging for resting-state and task-based fMRI 2. This is illustrated in Fig. 1 during a retinotopic mapping experiment which consists in mapping the retina to the primary visual cortex. These results have been obtained at a 1mm isotropic resolution both for EPI and SPARKLING acquisitions.
The image shows brain activity data for two volunteers (V3 and V4) using two imaging techniques (3D-EPI and 3D-SPARKLING). The data is presented both unsmoothed and smoothed. The left and right brain hemispheres are labeled L and R, respectively. Red and blue spots indicate areas of brain activity, with the left side of the color sphere representing blue and the right side representing red. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.2 Deep Learning for 3D Non-Cartesian MR Image reconstruction
Participants: Asma Tanabene, Chaithya Giliyar Radhakrishna, Philippe Ciuciu.
External Collaborators: Aurélien Massire [Siemens-Healthineers, France].
Deep learning and notably unrolled neural netowrk architectures have shown great promise for MRI reconstruction from undersampled data. However, there is a lack of research on validating their performance in the 3D parallel imaging acquisitions with non-Cartesian undersampling. In addition, the artifacts and the resulting image quality depend on the under-sampling pattern. To address this uncharted territory, in 2024 we extended the Non-Cartesian Primal-Dual Network (NC-PDNet) 170, to a 3D multi-coil acquisition setting. We evaluated the impact of channel-specific versus channel-agnostic training configurations and examined the effect of coil compression. Finally, using the publicly available Calgary-Campinas dataset, we benchmarked four distinct non-Cartesian undersampling patterns, with an acceleration factor of six. Our results in Fig. 2 showed that NC-PDNet trained on compressed data with varying input channel numbers achieves an average PSNR of 42.98dB for 1 mm isotropic 3- channel whole-brain 3D reconstruction. With an inference time of 4.95sec and a GPU memory usage of 5.49 GB, our approach demonstrates significant potential for clinical research application.
The image consists of six brain MRI scans displayed in two rows. The top row shows full sagittal brain images with a red square highlighting a specific area. The bottom row shows magnified views of the highlighted area from the top row. From left to right, the columns represent different imaging techniques: Ground truth, 3D Radial, 3D Cones, TPI, GoLF-SPARKLING, and GoLF-SPARKLING (NO Coil Compression). Metrics (PSNR and SSIM) are shown above each respective image, indicating image quality. Red arrows in the 3D Radial and TPI magnified views point to noticeable artifacts or differences compared to the ground truth. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.3 Fast reconstructions of ultra-high resolution MR data from the 11.7T Iseult scanner
Participants: Chaithya Giliyar Radhakrishna, Philippe Ciuciu.
External Collaborators: Alexandre Vignaud [CEA/NeuroSpin], Franck Mauconduit [CEA/NeuroSpin].
Open-source MR reconstruction tools often fail to efficiently utilize GPU resources and lack support for generalized GRAPPA implementations. Many tools are limited to 2D or 3D reconstruction, and few incorporate advanced techniques such as 2D-CAIPIRINHA, which enhances imaging capabilities. Our new open source gGRAPPA GPU accelerated Python package aims to provide a fast, flexible, open-source tool for generalized GRAPPA/CAIPI reconstruction 47. Using PyTorch, gGRAPPA runs multiple convolutional windows in batch mode to optimize GPU memory usage and accelerate reconstruction times. gGRAPPA achieves up to a 65x speedup over CPU implementations and a 6x speedup compared to non-batched GPU methods, enabling efficient and fast reconstruction of MRI scans. This tool has allowed us to outperform the Siemens image reconstructor, in terms of speed, on the world premiere 11.7T MR system (Iseult scanner available at NeuroSpin) to reconstruct the first in vivo weighted MR images at a 200-µm in plane resolution.
The image shows two brain MRI scans side by side. Both scans display axial cross-sections of the brain with visible structures like ventricles and gyri. The left scan is labeled "gGRAPPA reconstruction" and the right one "Scanner reconstruction." The scans appear similar but might show slight differences in image quality and clarity. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.4 SNAKE-fMRI: A realistic fMRI data simulator for high resolution functional imaging
Participants: Pierre-Antoine Comby, Philippe Ciuciu.
External Collaborators: Alexandre Vignaud [CEA/NeuroSpin].
Functional Magnetic Resonance Imaging (fMRI) has emerged as a powerful non-invasive tool in neuroscience, enabling neuroscientists to understand human brain functions. However, fMRI acquisition and image reconstruction techniques are complex to optimize and benchmark due to the lack of ground truth that produces absolute and quantitative metrics. Repeating in-vivo experiments may face the issue of limited reproducibility, which is time-consuming and expensive. fMRI simulators have been developed to generate synthetic fMRI images, where brain responses are artificially added to existing or artificial data. However, they don’t simulate the complete MR acquisition process, lack flexibility, integration with post-processing, and computational efficiency. Exploring new acceleration schemes in the acquisition setting and innovative reconstruction methods with these tools is not feasible. To address these unmet needs, in 20204 we have developed SNAKE-fMRI 15, an open-source fMRI simulator that operates in both image and k-space domains to yield realistic synthetic fMRI data. Its flexibility allows us to investigate various acquisition setups regarding SNR and acceleration factors to reach higher spatial and temporal resolution and validate reconstruction methods against those scenarios. Its key principles are summarized in Fig. 4 and some comparative results are shown in Fig. 5.
The image illustrates the process of MRI brain activity imaging over time. At the top, a graph shows simulated brain activity and its measurement intervals (TR Vol.). The middle section depicts sequential brain images (labeled 1 to 7) taken during these intervals. Below this, a diagram explains how different tissue types contribute to single-shot acquisitions in k-space, shown as color-coded horizontal lines. The bottom part displays the acquired k-space data over one TR volume, correlating with the sequential images above. The overall concept demonstrates how MRI captures brain activity by assembling data from various tissue types over time. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
The image displays brain scans in a 3x3 grid, comparing different conditions and methods. The top row is labeled "dynamic" with conditions: COLD, REFINED, and WARM. The bottom row is labeled "static" with the same conditions. Each scan shows brain activity with color-coded z-scores, indicating varying levels of activation. Additional brain outlines with contour lines are overlaid on the scans highlighting specific regions of interest. The side views of the brain are also provided for better spatial context. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
The interest of this simulator will be to provide ground truth data to train deep learning models for fMRI reconstruction in 2025.
7.5 NeuroConText: Contrastive text-to-brain mapping for neuroscientific literature
Participants: Bertrand Thirion, Demian Wassermann, Fatemeh Ghayem, Raphael Meudec.
Hundreds of neuroscientific articles are published annually, highlighting the continuous growth and expansion of knowledge in this field. These contributions from scientists and researchers provide new insights and findings that enhance our understanding of brain functions. Meta-analysis is a statistical tool that combines results from multiple studies to improve the reliability and generalizability of neuroscientific findings. It serves three key purposes: First, it synthesizes information from the literature to build the state of the art by offering a consolidated view of what is currently known. This allows researchers to see where the field stands collectively and highlights consensus or inconsistencies. Second, meta-analysis provides context to interpret new results by comparing novel experimental data with existing patterns in the meta-analysis of the literature, which clarifies how new data align with or deviate from established findings. Third, meta-analysis generates hypotheses on candidate brain regions or relevant cognitive domains by revealing patterns that might be central to a phenomenon.
In 67, we introduced NeuroConText, a novel coordinate-based meta-analysis (CBMA) tool to bridge the three heterogeneous modalities commonly found in neuroscientific studies: text, reported brain activation coordinates, and brain images. NeuroConText uses neuroscientific articles to extract their text and activation coordinates. We benefited from the embeddings of advanced large language models (LLM) for text feature representation. Additionally, we used Kernel Density Estimation (KDE) to reconstruct brain maps from the coordinates 179, 178. To address the high dimensionality of the brain images reconstructed by KDE, we employed the dictionary of functional modes (DiFuMo), a probabilistic atlas that effectively reduces data dimensionality 110.
Then, NeuroConText defines a shared latent space between text and coordinates, using contrastive learning to retrieve the brain activation coordinates corresponding to the input text. NeuroConText can analyze long texts, leveraging the complete information in articles' text to enhance the accuracy of text-to-brain associations. By incorporating advanced language models like Mistral-7B, it processes complex neuroscientific text and extracts the semantic in the text 135. NeuroConText considerably outperforms existing regression-based state-of-the-art methods NeuroQuery and Text2Brain in associating text with brain activations, achieving a threefold improvement in the retrieval task. To improve our understanding of the internal mechanisms of the NeuroConText model, we also evaluated its ability to reconstruct brain activation contrasts from text latent representations using descriptions of the NeuroVault dataset 125. The quality of these reconstructed activation maps is found to be comparable with state-of-the-art baselines.
(a) Training of NeuroConText contrastive model on neuroscientific publications.
(b) Brain encoding of a query through the NeuroConText text latent representation.
The image displays six brain scans arranged in a 2x3 grid. Each scan shows colored areas overlaid with brain structure outlines. The top row represents dynamic conditions labeled as "COLD," "REFINED," and "WARM," while the bottom row shows static conditions with the same labels. Color scales on the right indicate z-scores ranging from -11 to 11, highlighting brain activity differences. The scans reveal varying levels of brain activation under different conditions. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
The image displays six brain scans arranged in a 2x3 grid. Each scan shows colored areas overlaid with brain structure outlines. The top row represents dynamic conditions labeled as "COLD," "REFINED," and "WARM," while the bottom row shows static conditions with the same labels. Color scales on the right indicate z-scores ranging from -11 to 11, highlighting brain activity differences. The scans reveal varying levels of brain activation under different conditions. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.6 Whole-brain modeling of dynamic causal circuits in human cognition using amortized variational inference
Participants: Demian Wassermann, Louis Rouillard, Letizia Levin-Diniz.
Main External Collaborators: Vinod Menon [Stanford University, USA], Weidong Cai [Stanford University, USA], Srikanth Ryali [Stanford University, USA], Luca Ambrogioni [Donders Institute, Netherlands].
Understanding dynamic mechanisms underlying cognition remains a major challenge in human neuroscience. Here, we develop, validate, and apply Multivariate Dynamical Systems Identification with Amortized Variational Inference (MDSI-AVI), a novel computational framework designed to address critical challenges in capturing asymmetric, context-dependent, whole-brain directed interactions while accounting for regional hemodynamic response variability in fMRI data. MDSI-AVI, which is a methodological advancement related to sections 3.2 and 3.3 of our research program, leverages simulation-based inference through forward and reverse variational inference to address the limitations of conventional variational methods in high-dimensional settings and its based on our previous developements. By averaging over uncertainty in hemodynamic response parameters using forward simulation, MDSI-AVI provides well-calibrated posteriors of directed connectivity that scale efficiently to networks with hundreds of nodes. Applied to Human Connectome Project data (N=728), MDSI-AVI reveals new insights into working memory mechanisms, identifying the dorsal anterior insula as a critical hub influencing activity at the whole-brain level. We demonstrate task-dependent modulation of causal influences, where the salience network drives frontoparietal network activity, which differentially influences the default mode and sensorimotor networks depending on working memory load. These whole-brain causal interactions distinguish task conditions with high accuracy and predict working memory performance. Our framework, illustrated in Fig. 7, demonstrates reproducible results across whole-brain parcellations, establishing MDSI-AVI as a robust tool for advancing our understanding of circuit dynamics in cognition and disease. This work is currently in press.
The image details a framework for estimating brain-wide task context-dependent dynamic causal interactions from fMRI using the MDSI-AVI model. Panel A explains the estimation process, showing task design, observed and latent signals, and interaction strength analysis across brain regions. Panel B presents the graphical representation of the MDSI-AVI model, including the generative model and the hybrid inference method for parameter estimation. Panel C outlines the analytic approach for validating and applying the MDSI-AVI model across three steps: simulated fMRI, rodent fMRI, and human task-fMRI, with goals, evaluations, and experimental analyses specified for each step. (Description generated at February 25th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.7 Brain-wide decoding of numbers and letters: Converging evidence from multivariate fMRI analysis and probabilistic meta-analysis
Participants: Demian Wassermann, Gaston Zanitti.
Main External Collaborators: Vinod Menon [Stanford University, USA], Hyesang Chang [Stanford University, USA].
Previous studies exploring category-sensitive representations of numbers and letters have predominantly focused on individual brain regions. This study expands upon this research through computationally rigorous whole-brain neural decoding using Elastic Net (ND-EN), facilitating the analysis of neural patterns across the entire brain with greater precision. To establish the robustness and generalizability of our results, we also conducted innovative probabilistic meta-analyses of the extant functional neuroimaging literature. The investigation comprised both an active task, requiring participants to distinguish between numbers and letters, and a passive task where they simply viewed these symbols. ND-EN revealed that, during the active task, a distributed network—including the ventral temporal-occipital cortex, intraparietal sulcus, middle frontal gyrus, and insula—actively differentiated between numbers and letters. This distinction was not evident in the passive task, indicating that the task engagement level plays a crucial role in such neural differentiation. Further, regional neural representational similarity analyses within the ventral temporal-occipital cortex revealed similar activation patterns for numbers and letters, indicating a lack of differentiation in regions previously linked to these visual symbols. Thus, our findings indicate that category-sensitive representations of numbers and letters are not confined to isolated regions but involve a broader network of brain areas, and are modulated by task demands. Supporting these empirical findings, probabilistic meta-analyses conducted with NeuroLang, related to section 3.2 of the research program, and the Neurosynth database reinforced our observations. Together, the convergence of evidence from multivariate neural pattern analysis and meta-analysis advances our understanding of how numbers and letters are represented in the human brain. We illustrate this contribution 21 in Fig. 8.
This image outlines a study comparing brain responses to letters and numbers. Panel A shows a sequence of digits with quizzes. Panel B presents a checkerboard task. Panel C depicts trials with letters and digits. Panel D shows accuracy and response time results, highlighting better performance with numbers. Panel E explains brain analysis methods, including whole-brain decoding and region-of-interest (ROI) analysis. Panel F describes forward meta-analysis. Panel G lists cognitive tasks (CogAt) and reverse meta-analysis methods. The study uses fMRI data and statistical methods to decode brain activity related to processing letters and numbers. (Description generated at February 25th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.8 Improving physiological signal processings for enhanced monitoring in general anaesthesia
Participants: External Collaborators: Jade Perdereau, Virginie Loison, Thomas Moreau, Fabrice Vallée [APHP, Inserm], Jerome Cartailler [Inserm, APHP], Jona Joachim [APHP, Inserm].
Monitoring vital signs during general anaesthesia is crucial for patient safety, yet current approaches face significant limitations. Non-invasive blood pressure measurements suffer from poor temporal resolution, while invasive arterial lines, despite their accuracy, carry substantial complication risks. To address this clinical need, we developed AnesthNet 25, a deep learning architecture designed for real-time mean arterial pressure (MAP) estimation using exclusively non-invasive sensors routinely available in operating rooms. By leveraging photoplethysmography (PPG), electrocardiogram (ECG), and other standard monitoring signals, AnesthNet provides continuous MAP estimation with high temporal resolution while avoiding the risks associated with invasive monitoring. The model was trained and validated on large-scale, open-source perioperative databases, demonstrating robust performance and reproducibility across diverse patient populations. This approach represents a significant step toward safer and more accessible hemodynamic monitoring in clinical practice.
The development of AnesthNet was made possible by our collaboration with APHP Lariboisière, and our involvement in the development of a comprehensive perioperative data platform, designed to support both real-time clinical applications and long-term machine learning research 70. To date, it allowed to collect over 42 TB of data encompassing 122,815 cases across multiple specialties including ICU and emergency settings. Beyond MAP estimation, this infrastructure supports other development in the team for physiological event detection, for instance our work on the UNHaP (Unmix Noise from Hawkes Processes) method 37, which jointly learns temporal structures in physiological events while removing spurious detections.
The image depicts a system for predicting mean arterial pressure (MAP) using photoplethysmogram (PPG) and electrocardiogram (ECG) signals. The process involves several steps: 1. **Input Signals**: PPG and ECG signals are collected at 125 Hz using a cuff device. 2. **Signal Processing**: Signals are processed to derive variables such as NRA, PI, and HR at 1 Hz. 3. **Causal Convolutions**: The signals undergo multiple layers of causal convolutions with increasing dilation rates and dropout layers to extract features. 4. **LSTM Blocks**: Processed signals are passed through concatenation and LSTM blocks for further feature extraction and temporal sequence learning. 5. **Prediction**: The final output is the predicted MAP. The illustration includes diagrams of convolutional layers, LSTM units, and an initialization step for the hidden state in LSTM, providing a comprehensive view of the predictive model. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.9 Clinical biomarkers for epilepsy
Participants: Sheng H Wang, Philippe Ciuciu.
External Collaborators: Matias Palva [Aalto University, Finland], Satu Palva [Neuroscience Center, Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Finland].
Postsurgical seizure freedom in drug-resistant epilepsy (DRE) patients varies from 30% to 80%, implying that in many cases the current approaches fail to fully map the epileptogenic zone (EZ). We aimed to advance a novel approach to better characterize epileptogenicity and investigate whether the EZ encompasses a broader epileptogenic network (EpiNet) beyond the seizure zone (SZ) that exhibits seizure activity. We first used computational modeling to test putative complex systems-driven and systems neuroscience-driven mechanistic biomarkers for epileptogenicity. We then used these biomarkers to extract features from resting-state stereo-electroencephalograms recorded from DRE patients and trained supervised classifiers to localize the SZ against gold standard clinical localization. To further explore the prevalence of pathological features in an extended brain network outside of the clinically identified SZ, we also used unsupervised classification. Supervised SZ classification trained on individual features achieved accuracies of 0.6–.07 area under the receiver operating characteristic curve (AUC).* Combining all criticality and synchrony features further improved the AUC to 0.85. Unsupervised classification discovered an EpiNet-like cluster of brain regions, in which 51% of brain regions were outside of the SZ. Brain regions in the EpiNet-like cluster engaged in interareal hypersynchrony and locally exhibited high-amplitude bistability and excessive inhibition, which was strikingly similar to the high seizure risk regime revealed by our computational modeling. The finding that combining biomarkers improves SZ localization accuracy indicates that the novel mechanistic biomarkers for epileptogenicity employed here yield synergistic information. On the other hand, the discovery of SZ-like brain dynamics outside of the clinically defined SZ provides empirical evidence of an extended pathophysiological EpiNet.
The image shows brain activity analysis comparing seizure-zone (SZ) and non-seizure-zone (nSZ) regions using SEEG (Stereo-EEG) traces. The top panels display the broad band, 4.0 Hz, and 80.0 Hz frequency traces from the anterior cingulate (SZ) and mid-front gyrus (nSZ). The middle panels illustrate Cohen's d values for various frequency bands, highlighting differences in bistability, E/I balance, local efficiency, and eigenvector centrality. The bottom panel presents a classification outcome for seizure zones using different feature sets, including criticality and synchronization metrics. The results indicate significant differences in brain dynamics between SZ and nSZ regions. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
7.10 Encoding of Numerosity With Robustness to Object and Scene Identity in Biologically Inspired Object Recognition Networks
Participants: Thomas Chapalain, Bertrand Thirion.
External Collaborators: Evelyn Eger [UNICOG-U992 - Neuroimagerie cognitive - Psychologie cognitive expérimentale ].
Number sense, the ability to rapidly estimate object quantities in a visual scene without precise counting, is a crucial cognitive capacity found in humans and many other animals. Recent studies have identified artificial neurons tuned to numbers of items in biologically inspired vision models, even before training, and proposed these artificial neural networks as candidate models for the emergence of number sense in the brain. But real-world numerosity perception requires abstraction from the properties of individual objects and their contexts, unlike the simplified dot patterns used in previous studies. Using novel synthetically generated photorealistic stimuli, we show that deep convolutional neural networks optimized for object recognition encode information on approximate numerosity across diverse objects and scene types, which could be linearly read out from distributed activity patterns of later convolutional layers of different network architectures tested. In contrast, untrained networks with random weights failed to represent numerosity with abstractness to other visual properties and instead captured mainly low-level visual features. Our findings emphasize the importance of using complex, naturalistic stimuli to investigate mechanisms of number sense in both biological and artificial systems, and they suggest that the capacity of untrained networks to account for early-life numerical abilities should be reassessed. They further point to a possible, so far underappreciated, contribution of the brain's ventral visual pathway to representing numerosity with abstractness to other high-level visual properties.
The image depicts a study on neural network models analyzing visual stimuli. Panel A shows the process of encoding input stimuli via a Convolutional Neural Network (CNN) and decoding it through ridge regression. Panel B categorizes stimuli into natural and artificial animals and tools, with coarse-grained generalization. Panels C and E present graphs comparing the performance of trained and untrained models in estimating features like numerosity and area. Panel D contrasts congruent and incongruent stimuli examples, illustrating how various features are represented. The overall concept explores how well these models can interpret and generalize visual information. (Description generated at February 6th, 2026 by Albert AI with the model Mistral-Small-3.2-24B)
8 Bilateral contracts and grants with industry
Participants: Philippe Ciuciu, Asma Tanabene, Thomas Moreau.
8.1 Bilateral contracts with industry
8.1.1 Siemens Healthineers & AI lab (Princeton, USA)
Since Fall 2019, Philippe Ciuciu has actively collaborated with the Siemens-Healthineers AI lab, led by Mariappan Nadar. In this context, a new CIFRE PhD student, Mrs Asma Tanabene, has joint the MIND team as a CIFRE PhD student under their joint supervision to work on 3D sclalable deep learning architecture for high-resolution multicoil MR image reconstruction at 3 Tesla and beyond. On top of the PhD funding, this contract has generated 50k€ for Mind, a grant that is hosted at CEA/NeuroSpin.
8.1.2 Saint Gobain Research (SGR)
There is currently a consulting contract between SGR and Mind (Thomas Moreau) to provide an expertise in machine learning to process temporal data, numerical optimization and scientific computing. The expertise is provided one half-day per month, in SGR offices, and it consists in scientific discussion sessions on the ML projects leaded by SGR data scientists.
8.1.3 Apple
A research collaboration between Apple (Pierre Ablin) and Mind (Thomas Moreau) has been established. The goal is to develop research ideas on bilevel optimization, in particular for the problem of data curation for the training of large models with massive and heterogeneous datasets. This collaboration is being funded by Apple (150k€) and allowed to hire a post-doc (Baptiste Goujaud).
8.2 Bilateral Grants with Industry
8.2.1 Google
Mind (Thomas Moreau) received a 30k€ donation from Google to support its open source activity around benchopt. In particular, the grant aims to support the organization of coding and benchmarking sprints around benchopt, the development of visualization tools, and the benchmarking of bilevel solvers, in particular the ones using jaxopt.
9 Partnerships and cooperations
9.1 International initiatives
9.1.1 Inria associate team not involved in an IIL or an international program
DANDI
Participants: Bertrand Thirion, Pierre-Louis Barbarant, Rémi Gau, Elizabeth Dupré.
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Title:
DANDI: Domain Adaptation for Neural Data Integration
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Partner Institution(s):
Université de Montréal, Canada
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Date/Duration:
2025-2027
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abstract
We propose to evaluate our ability to recover from a known distribution shift when transferring from a healthy to a clinical population, assessing the impact of data availability and methods for domain adaptation procedures. Specifically, we will evaluate whether training models on individual participants can effectively transfer information (1) within a source population, and (2) from a source population to a target population. For such approaches to scale on high-dimensional datasets, the best approach is the joint specification of transformation models mapping a learned template to individual datasets. To assess the feasibility of the procedure, we will rely on exceptionally rich brain imaging data available to the participants: the Courtois-Neuromod dataset and the target dataset, the Psychosis Research using Integrated Serial Measurements (PRISME), was collected from 12 participants who currently have or who previously had a diagnosis of active psychosis, with clinical and neuroimaging data collected monthly for a year, suing the same sequences as Courtois Neuromod.
The associate team is also strongly involved insoftware development, in particular with the development of Nilearn.
9.2 European initiatives
9.2.1 Horizon Europe
EBRAINS 2.0
EBRAINS 2.0 project on cordis.europa.eu
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Title:
EBRAINS 2.0: A Research Infrastructure to Advance Neuroscience and Brain Health
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Duration:
From January 1, 2024 to December 31, 2026
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Partners:
- INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET AUTOMATIQUE (INRIA), France
- MEDIZINISCHE UNIVERSITAET WIEN, Austria
- CONVELOP - COOPERATIVE KNOWLEDGE DESIGN GMBH, Austria
- REGION HOVEDSTADEN (REGIONH), Denmark
- HEINRICH-HEINE-UNIVERSITAET DUESSELDORF (UDUS), Germany
- THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE, United Kingdom
- INSTITUT NATIONAL DE LA SANTE ET DE LA RECHERCHE MEDICALE (INSERM), France
- INSTITUT NATIONAL DE LA SANTE ET DE LA RECHERCHE MEDICALE (INSERM), France
- UNIVERSITE LYON 1 CLAUDE BERNARD, France
- KUNGLIGA TEKNISKA HOEGSKOLAN (KTH), Sweden
- THE UNIVERSITY OF MANCHESTER (UNIVERSITY OF MANCHESTER), United Kingdom
- EUROPEAN ACADEMY OF NEUROLOGY, Austria
- FORSCHUNGSZENTRUM JULICH GMBH (FZJ), Germany
- KONINKLIJKE NEDERLANDSE AKADEMIE VAN WETENSCHAPPEN - KNAW (KNAW), Netherlands
- UNIVERSITEIT GENT (UGent), Belgium
- TECHNISCHE UNIVERSITAET MUENCHEN (TUM), Germany
- COMMISSARIAT A L ENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES (CEA), France
- EBRAINS (EBRAINS), Belgium
- ASSISTANCE PUBLIQUE HOPITAUX DE PARIS, France
- RUPRECHT-KARLS-UNIVERSITAET HEIDELBERG (UHEI), Germany
- ATHINA-EREVNITIKO KENTRO KAINOTOMIAS STIS TECHNOLOGIES TIS PLIROFORIAS, TON EPIKOINONION KAI TIS GNOSIS (ATHENA - RESEARCH AND INNOVATION CENTER), Greece
- UNIVERSITAET BERN, Switzerland
- RISE RESEARCH INSTITUTES OF SWEDEN AB (RISE), Sweden
- UNIVERSITA DEGLI STUDI DI TORINO (UNITO), Italy
- UNIVERSITEIT MAASTRICHT, Netherlands
- HITS GGMBH (HITS), Germany
- ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (EPFL), Switzerland
- UNIVERSITA DEGLI STUDI DI PADOVA (UNIPD), Italy
- CENTRE HOSPITALIER UNIVERSITAIRE VAUDOIS (CHUV), Switzerland
- NORGES MILJO-OG BIOVITENSKAPELIGE UNIVERSITET (NMBU), Norway
- LIETUVOS SVEIKATOS MOKSLU UNIVERSITETAS (LSMU), Lithuania
- UNIVERSITAT TRIER, Germany
- MEDIZINISCHE UNIVERSITAT INNSBRUCK (MUI), Austria
- TAMPEREEN KORKEAKOULUSAATIO SR (TAMPERE UNIVERSITY), Finland
- UNIVERSITE GRENOBLE ALPES (UGA), France
- CONSIGLIO NAZIONALE DELLE RICERCHE (CNR), Italy
- UNIVERSITE DE BORDEAUX (UBx), France
- UNIVERSITA DEGLI STUDI DI PAVIA (UNIPV), Italy
- FONDAZIONE PER LA RICERCA BIOMEDICA AVANZATA ONLUS (VIMM), Italy
- EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH (ETH Zürich), Switzerland
- CHARITE - UNIVERSITAETSMEDIZIN BERLIN, Germany
- UNIVERSITAETSKLINIKUM HAMBURG-EPPENDORF (UKE), Germany
- UNIVERSITETET I OSLO (UNIVERSITY OF OSLO), Norway
- POLITECNICO DI MILANO (POLIMI), Italy
- UNIVERSITA DEGLI STUDI DI MILANO (UMIL), Italy
- KAROLINSKA INSTITUTET (KAROLINSKA INSTITUTE), Sweden
- FONDEN DEMOCRACY X (DEMOCRACY X), Denmark
- KLINIKUM DER TECHNISCHEN UNIVERSITÄT MÜNCHEN (TUM KLINIKUM) (TUM-MED), Germany
- PROTISVALOR MEDITERRANEE SAS (PVM), France
- UNIVERSIDAD REY JUAN CARLOS (URJC), Spain
- UNIVERSITE D'AIX MARSEILLE (AMU), France
- UNIVERSITY COLLEGE LONDON, United Kingdom
- CINECA CONSORZIO INTERUNIVERSITARIO (CINECA), Italy
- UNIVERSITAETSKLINIKUM FREIBURG (UKLFR), Germany
- CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS (CNRS), France
- KATHOLIEKE UNIVERSITEIT LEUVEN (KU Leuven), Belgium
- CODEMART SRL (CODEMART), Romania
- UNIVERSIDAD POLITECNICA DE MADRID (UPM), Spain
- LABORATORIO EUROPEO DI SPETTROSCOPIE NON LINEARI (LENS), Italy
- AZIENDA SANITARIA UNIVERSITARIA FRIULI CENTRALE (AZIENDA SANITARIA UNIVERSITARIA FRIULI CENTRALE), Italy
- TECHNISCHE UNIVERSITAET DRESDEN (TUD), Germany
-
Inria contact:
Bertrand Thirion
- Coordinator:
-
Summary:
EBRAINS is a collaborative European Research Infrastructure designed to advance and accelerate progress in neuroscience and brain health. This innovative infrastructure, a legacy of the Human Brain Project (HBP), is an ecosystem where researchers, clinicians and experts from various disciplines converge to explore and analyze brain complexity – from molecular and cellular levels to the functioning of the entire organ. Therefore, the project aims to create a new standard for brain atlases from the micro- to the macro-scale, link foundational multi-level data and connectomes in the healthy and pathological brain with atlases and models, create digital twins through modelling and simulation as well as unique, excellent, and preferred services for FAIR neuroscience data. The overarching goal of EBRAINS 2.0 is to foster a deeper understanding of brain structure and function with dedicated and mature software tools, to facilitate the development of more effective treatments, new drugs, diagnostics and preventive measures for neuro-psychiatric disorders. We expect that EBRAINS 2.0 catalyzes progress in the field of large-scale models running on HPC towards Exascale and leads to innovative solutions for neuro-inspired computing, and cognitive technologies such as neurorobotics and AI. Sophisticated digital modeling and data analytics capabilities will benefit communities beyond neuroscience, such as biomedicine. We will advance EBRAINS technology, platform services and the base infrastructure roadmap, educate and train a new community of users and developers from academia, industry and SMEs, and ensure knowledge transfer. EBRAINS 2.0 will become the neuroscience hub in the European infrastructure landscape, through building strong links with the European data spaces, EOSC and EuroHPC JU, centers of excellences and other initiatives. Globally, EBRAINS 2.0 will make a strong contribution to the new era of digital neuroscience and foster European leadership in this field.
SafeREG
SafeREG project on cordis.europa.eu
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Title:
Probabilistic Non-Rigid Registration for Safe Brain Tumor Resection
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Duration:
From August 1, 2024 to July 31, 2026
-
Partners:
- INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET AUTOMATIQUE (INRIA), France
-
Inria contact:
Demian Wassermann
- Coordinator:
-
Summary:
Brain tumors strike people in the prime of life. Surgical resection is the initial treatment for nearly all brain tumors and aims at maximizing the extent of tumor resection while preserving the patient's cognitive function. To optimize this tradeoff, neuronavigation systems have been developed to provide intraoperative guidance to surgeons. These systems allow for the visualization of the position of surgeons' surgical tools relative to the tumor and critical brain areas visible in preoperative Magnetic Resonance Imaging. However, these systems become inaccurate as the surgery progresses since they do not account for brain deformation and tissue resection occurring during surgery.
In an interdisciplinary effort, project SafeREG combines the researcher's background to the expertise of computational scientists from INRIA and clinicians from Parisian hospitals. Its objective is to invent a novel image registration methodology with intraoperative ultrasound that is rich enough to capture complex deformations occurring at the tumor and resection cavity boundaries, fast enough to be employable clinically, and interpretable enough for informed decision-making by neurosurgeons. This will be accomplished by pushing the envelope of scientific knowledge in (1) cross-modality domain adaptation for weakly- and unsupervised image segmentation; (2) modality-invariance representation learning using contrastive learning; (3) non-rigid registration with discrete probabilistic methods; (4) simulated-based variational inference for registration uncertainty quantification that leverages biomechanical knowledge. This research has the potential to deliver accurate and informed image-guided surgery, conferring a lower risk of new neurologic deficits and improved patient prognosis. Beyond neurosurgery, it has broad applications to additional areas of image-guided therapy, including spine, liver, and prostate surgery.
9.3 National initiatives
CEA Audace at-risk research program
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Title:
BrainSync
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Duration:
11/2024 -> 04/2029
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Coordinator:
Philippe Ciuciu (CEA/DRF/JOLIOT/NEUROSPIN/MIND), Saclay
-
Partners:
- CEA/DRF/JOLIOT/NEUROSPIN (BAOBAB, UNICOG), Saclay
- CEA/DRT/LETI/CLINATEC, Grenoble
- CEA/DRT/LIST/DSCIN, Grenoble
- Inria-CEA MIND, Palaiseau
- APHP, FHU NeuroVasc, Paris-Nord
- GHU Paris Neuroscience & Psychiatry
- CHU Grenoble-Alpes
- LPNC, University Grenoble-Alphes & CNRS
- CHU St Etienne
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Inria contact:
Philippe Ciuciu
-
Summary:
The project aims to understand the learning mechanisms that enable the human brain to adapt to cognitive demand via the flexible recruitment of different regions and connections, thus enabling exploration of an uncertain and changing environment. Understanding these mechanisms in healthy subjects, coupled with the creation of a high-resolution anatomical-functional digital brain atlas of a cohort of post-acute stroke patients (MOTIF-STROKE clinical trial), will enable us to propose AI models predictive of upper limb motor recovery in these patients, and therapeutic innovations (use of neuroprostheses) for a small number of them in a second clinical trial. Clinical evaluation of relearning processes will be based on the use of incremental and adaptive artificial intelligence (AI) algorithms linked to neuroplasticity processes.
This project has received a funding of 5M€ for a period of 4.5 years starting in November 2024 with a go/no-go positioned after a period of 30 months (04/30/2027).
CEA BlueSky project
-
Title:
Brain & Computers
-
Duration:
2023 -> 2026
-
Coordinator:
Philippe Ciuciu (CEA/DRF/JOLIOT/NEUROSPIN/MIND), Saclay
-
Partners:
- CEA/DRF/JOLIOT/NEUROSPIN (BAOBAB, UNICOG), Saclay
- CEA/DRT/LETI/CLINATEC, Grenoble
- CEA/DRT/LIST/DSCIN, Grenoble
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Inria contact:
Philippe Ciuciu
-
Summary:
Artificial Intelligence (AI) is now capable of approaching human performance in tasks such as visual recognition, classification (i.e., decision-making), and even textual or visual production (e.g., GPT-4). Understanding the human brain mechanisms of learning and decision-making in an uncertain environment remains a major scientific challenge in neuroscience. This understanding will enable the development of AI architectures that replicate brain circuits. Additionally, in clinical applications, it can lead to a generational leap in the design of neuroprostheses. These neuroprostheses hold great promise for improving the quality of life for individuals affected by spinal cord injuries (approximately 30% of cases).
The two main objectives of this BlueSky project complement each other. On one hand, in healthy subjects, the goal is to design computational models based on AI that encode these cerebral functions to gain a more precise understanding of the associated brain activity. On the other hand, the objective is to enable a greater number of patients to control neuroprostheses autonomously through AI, making these medical devices more widely accepted as a therapeutic solution for motor rehabilitation. Tackling such a challenge is not without risks and requires expanding knowledge in neuroscience, surpassing current technological and clinical limits. It also calls for strong synergies among the various CEA institutes involved (Joliot, LETI, and LIST) and their academic (Inserm, Inria, Universities Paris-Saclay, and Grenoble Alpes) and clinical partners (CHU Grenoble-Alpes).
This project has received a funding of 1.5M€ for the 2023-2025 period.
ANR DARLING
-
Title:
DARLING: Distributed adaptation and learning over graph signals
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Duration:
2020 -> 2025 (extended)
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Coordinator:
Cédric Richard (cedric.richard@unice.fr),Professor 3IA Senior Chair in UCA
-
Partners:
- Université Côte d'Azur Nice, France
- CNRS, École Normale Supérieure, Lyon, France
- Gipsa-lab, UMR 5216, CNRS, UGA, Grenoble, France
- CentraleSupélec, University of Paris-Saclay, Gif-sur-yvette, France
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Inria contact:
Philippe Ciuciu
-
Summary:
The DARLING project will aim to propose new adaptive learning methods, distributed and collaborative on large dynamic graphs in order to extract structured information of the data flows generated and/or transiting at the nodes of these graphs. In order to obtain performance guarantees, these methods will be systematically accompanied by an in-depth study of random matrix theory. This powerful tool, never exploited so far in this context although perfectly suited for inference on random graphs, will thereby provide even avenues for improvement. Finally, in addition to their evaluation on public data sets, the methods will be compared with each other using two advanced imaging techniques in which two of the partners are involved: radio astronomy with the giant SKA instrument (Obs. Côte d'Azur) and MEG brain imaging (Inria MIND at NeuroSpin, CEA Saclay). Sheng Wang as a postdoc in MIND and Merlin Dumeur as a MIND PhD student in co-tutelle with Matias Palva from Aalto University, Finland are actually involved in the processing of MEG and S/EEG time series on graphs, notably to analyze scale-free (i.e. critical and bistability) phenomena across these graphs and extract potentially new biomarkers for characterizing the pathophysiology of epileptogenic zone (EZ) in drug resistant epilepsy.
ANR VLFMRI
-
Title:
VLFMRI: Very low field MRI for babies
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Duration:
2021 -> 2025
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Coordinator:
Claude Fermon (CEA Saclay, DRF/IRAMIS/SPECT)
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Partners:
- CEA/SHFJ/BIOMAPS, Orsay, France
- CEA/NeuroSpin, Gif-sur-Yvette, France
- APHP Robert Debré hospital, Paris, France
- APHP Bicêtre hospital, Kremlin-Bicêtre, France
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Inria contact:
Philippe Ciuciu
-
Summary:
VLFMRI aims at developing a very low-field Magnetic Resonance Imaging (MRI) system as an alternative to conventional high-field MRI for continuous imaging of premature newborns to detect hemorrhages or ischemia. This system is based on a combination of a new generation of magnetic sensors based on spin electronics, optimized MR acquisition sequences (based on the SPARKLING patent, Inria-CEA MIND team at NeuroSpin) and a open and compatible system with an incubator that will allow to achieve an image resolution of 1mm on a whole baby body in a short scan time. This project is a partnership of three academic partners and two hospital departments. The different stages of the project are the finalization of the hardware development and software system, preclinical validation on small animals and clinical validation. Kumari Pooja has been hired in January 2022 as research engineer in MIND to interact with the coordinator of this ANR project, Claude Fermon and design new accelerated acquisition methods for verly low field MRI. Preliminary encouraging results allow us to retrospectively accelerate MRI acquisition by a factor of 10 without degrading image quality at 2mm isotropic resolution.
ANR MICBrainPres
-
Title:
MicBrainPres: Distributed adaptation and learning over graph signals
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Duration:
2023 -> 2026
-
Coordinator:
Demian Wassermann
-
Partners:
- Brain and Spine Institute, Paris, France
- CNRS, Université de Paris, Paris, France
-
Inria contact:
Demian Wassermann
-
Summary:
The main goal of this project is to harness the latest advances on machine learning-based neuroimage processing technologies to improve function-preserving brain tumour resection. Identifying eloquent brain regions is fundamental to performing tumour resection while preserving a maximum level of cognitive function. Despite the sustained advance in predicting subject-level cognitive abilities from neuroimaging data, current approaches lack sensitivity and specificity in identifying eloquent brain regions. This hinders neuroimaging's usefulness for pre-surgical planning as a tool to predict the preservation of cognitive function after tumour resection. In this project, we propose that using subject-specific parcellations, derived from functional and diffusion MRI through deep-learning technologies, will achieve the needed sensitivity and specificity to locate eloquent areas pre-surgically and to predict cortical reshaping after tumour resection.
ANR EBUL
-
Title:
EBUL: Event-based Unsupervised Learning for Physiological Signals
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Duration:
2023 -> 2027
-
Coordinator:
Thomas Moreau
-
Partners:
- INRIA MIND, Gif-sur-Yvette, France
-
Inria contact:
Thomas Moreau
-
Summary:
Sensor-based body monitoring is now routine clinical care. The resulting records are called physiological signals. While enormous quantities of signals are collected every day, the cost and time necessary to clean and annotate them is prohibitive to constitute large labeled databases. When working with physiological signals, extra sources of information are the events surrounding the recordings. Events are external phenomena that impact the signal and can correlate with the prediction task considered. EBUL propose to develop novel unsupervised learning techniques to process such records based on the notion of events, and to apply them to process general anesthesia records collected in Paris hospital Lariboisière. The methodology of the project relies on the development of novel point process models adapted to capture the distribution of physiological events, and their coupling with event detection algorithms. This will provide novel signal representations based on the distribution of events inside them, which are simpler to analyze and fine tune to derive predictive bio-markers.
The EBUL project is organized around 3 objectives:
- Develop novel point process models for physiological signals
- Learn joint models for signals and events
- Develop high-quality models for general anesthesia that can reach clinical research
ANR BenchArk
-
Title:
BenchArk: An efficient and robust benchmarking suite for AI
-
Duration:
2024 -> 2028
-
Coordinator:
Thomas Moreau, Mathurin Massias, Joseph Salmon
-
Partners:
- INRIA MIND, Gif-sur-Yvette, France
- INRIA OCKHAM, Lyon, France
- Université de Montpellier, Montpellier, France
-
Inria contact:
Thomas Moreau
-
Summary:
Numerical evaluation of novel methods, a.k.a. benchmarking, is a pillar of the scientific method in machine learning. However, due to practical and statistical obstacles, the reproducibility of published results is currently insufficient: many details can invalidate numerical comparisons, from insufficient uncertainty quantification to improper methodology. In 2022, the benchopt initiative provided an open source Python package together with a framework to seamlessly run, reuse, share and publish benchmarks in numerical optimization. In this project, we aim at bringing benchopt to the whole machine learning community, making it a new standard in benchmarking by empowering researchers and practitioners with efficient and valid benchmarking methods. Our goal is to ensure reproducibility and consistency in model evaluation. We will federate the machine learning community to develop informative and statistically valid benchmarks, while providing methods to reduce identified hurdles in implementing such practices. The results of the project will be integrated in the open source benchopt library.
Brain Health Trajectories
-
Title:
Brain Health Trajectories
-
Duration:
2023 -> 2028
-
Coordinator:
Viktor Jirsa, INS Marseille
-
Partners:
- INSERM Délégation Provence-Alpes-Côte d'Azur et Corse
- CNRS IDF Sud (Gif)
- Université d'Aix-Marseille
- CHU de Grenoble
- CEA, DRF, Joliot, Neurospin
- INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET AUTOMATIQUE
-
Inria contact:
Bertrand Thirion
-
Summary:
This project is part of PEPR Santé Numérique. The Brain Health Trajectories project is part of the PEPR Santé numérique program, a major research initiative of the French government as part of the France 2030 investment plan.
The project prioritizes the early identification of individuals at risk of developing a disease, so they can receive appropriate treatment before the disease develops or at least adapt their lifestyle to delay the onset of the pathology and slow down the progression of impairment. It aims to develop tools to characterize individuals' brain health and lay the foundation for a platform for screening, decision-making within the population, and prognostic monitoring of treatment efficacy.
ANR VITE
-
Title:
VITE: Explainable AI through Variable Importance Tests
-
Duration:
2024 -> 2027
-
Coordinator:
Bertrand Thirion
-
Partners:
- INRIA MIND, Gif-sur-Yvette, France
- Université de Toulouse, Toulouse, France
- Université de Montpellier, Montpellier, France
-
Inria contact:
Bertrand Thirion
-
Summary:
The VITE project aims to develop new statistical methods to interpret complex machine learning models, particularly in high-dimensional settings such as neuroimaging and genomics. The focus will be on creating variable importance tests that can provide insights into the contributions of individual features to model predictions. By leveraging recent advances in statistical theory and computational techniques, the project seeks to enhance the interpretability of AI models, making them more transparent and trustworthy for applications in healthcare and other critical domains.
ANR SPEAKOUT
-
Title:
SPEAKOUT: Statistical and machine learning methods for decoding speech from brain signals
-
Duration:
2025 -> 2028
-
Coordinator:
Anne-Lise Giraud
-
Partners:
- INRIA MIND, Gif-sur-Yvette, France
- Institut de l'audition, Paris, France
- institut du cerveau, Paris, France
-
Inria contact:
Bertrand Thirion
-
Summary:
The SPEAKOUT project aims to develop advanced statistical and machine learning methods to decode speech from brain signals. By analyzing neural activity associated with speech production and perception, the project seeks to create models that can accurately interpret and reconstruct spoken language from brain data. This research has the potential to revolutionize communication for individuals with speech impairments, enabling them to express themselves through brain-computer interfaces. The project will leverage cutting-edge techniques in signal processing, deep learning, and neuroscience to achieve its goals.
10 Dissemination
Participants: Demian Wassermann, Bertrand Thirion, Philippe Ciuciu, Thomas Moreau, Chaithya Giliyar Radhakrishna.
10.1 Promoting scientific activities
10.1.1 Scientific events: organisation
-
Thomas Moreau:
Co-organized the NeurIPS 2025 (San Diego) workshop on Foundation Models for Time Series, and the Open Source Conference In academIa on open source development and maintenance in 2025. He was also a member of the organizing committee of two international workshops at CIRM, Learning and Optimization in Luminy 2022 and 2024, and the co-founder and co-organizer of the Séminaire Palaisien, a monthly seminar gathering around 35 researchers from the Saclay area working on statistics and machine learning since 2019.
-
Bertrand Thirion:
Co-organized the CogBases Workshop in 2025, the NeuroDecoder workshop, the Explanability for high-dimensional statistics.
10.1.2 Journal
Member of the editorial boards
-
P. Ciuciu
Associate Editor (AE) for IEEE Transactions on Medical Imaging (TMI), Senior Area Editor for IEEE Open Journal on Signal Processing, AE for Frontiers in Neuroscience, section Brain Imaging Methods.
-
B. Thirion
Associate Editor (AE) for Medical Image Analysis (MIA) and Transactions on Machine Learning Research.
Reviewer - reviewing activities
-
P. Ciuciu
IEEE Transactions on Medical Imaging, IEEE Transactions on Cloud Computing, Magnetic Resonance in Medicine, NeuroImage.
-
B. Thirion
NeuroImage, MEdIA, IEEE Transactions on Medical Imaging, Brain Structure and Function, Human Brain Mapping, Nature Communications.
-
C. Giliyar Radhakrishna
Magnetic Resonance in Medicine, IEEE Transactions on Medical Imaging.
-
T. Moreau
IEEE Transactions on Signal Processing.
-
Demian Wassermann:
Reviewer for Funding Institutions: H2020, ANR (France), Netherlands Organisation for Scientific Research, National Agency for Scientific and Technological Promotion (Argentina). Reviewer for NeuroImage, Nature Communications, Nature Communications Biology, IEEE Transactions in Medical Imaging, Medical Image Analysis.
10.1.3 Invited talks
-
B.Thirion
- April 2025: Invited talk at Bilkent University, Ankara, Turkey.
- March 2025: Invited talk at the deep phenotyping workshop, Paris, France.
- January 2025: Invited talk at the Académie des Sciences, Paris, France.
- June 2025: Invited talk at Sanofi, Gentilly, France.
- April 2025: Invited talk at Université Grenoble Alpes, Grenoble, France.
- December 2025: Invited talk at the Morocco Academy of Sciences, Rabat, Morocco.
- March 2025: presentation of Nilearn development at OSCII workshop, Aussois, France.
- June 2025: presentation at ASIC workshop, Saint Gervais, France.
- Philippe Ciuciu:
-
Thomas Moreau:
- November 2025 – Joint invited talk for the Open Science Days and journée de la recherche frugale, Grenoble
- September 2025 – Inverse Problem and Imaging, CIRM, Luminy
- June 2025 – Plenary talk for Journée de la donnée, AMDAC Ministère de la santé, Paris
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Demian Wassermann:
- 2025: Neurofunctional Imaging Group – Université de Bordeaux 2025: Neuroscience Through the Lens of Machine Learning
- 2025: UCL Department of Computer Science (UK): Linking Neuroimaging and Cognition: from Automated Meta Analyses to Subject-Specific Prediction Through Probabilistic Modelling
10.1.4 Scientific expertise
-
B.Thirion
- Expert for the European Research Council (ERC) in the panel PE6
- Member of the Inria-Académie des Sciences joint committee for yearly prizes
10.1.5 Research administration
-
P. Ciuciu
- Member of the Board of Directors at NeuroSpin (CEA).
- Member of the team leaders committee at Inria Saclay Ile-de-France
- Member of the steering committee of the CEA cross-disciplinary research program on numerical simulation and AI.
-
B. Thirion
- Délégué Scientifique of Inria Saclay Center until September 2025.
- Member of ENS Paris-Saclay Scientific Council
- Member of Telecom Sud Paris Scientific Council
- Member of Inria Commission évaluation
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D. Wassermann
- Deputy Director of the DataIA Institute (Université Paris Saclay)
10.2 Teaching - Supervision - Juries - Educational and pedagogical outreach
-
P. Ciuciu
- Tutorial presenter at the 2024 EUSIPCO conference: Computational MRI in the Deep Learning Era: The Two Facets of Acquisition and Image Reconstruction.
- Lecturer at the Institut d'Optique Graduate School (3rd year, Signal & Images major).
- Lecturer at the M2 ATSI (CentraleSupelec, ENS Paris-Saclay): Medical imaging course.
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D. Wassermann
- Master MVA (École Polytechnique, École Normale Superiore, Centrale Supelec): Graphical Models
- Master in Biomedical Engineering (Université Paris Descartes): Quantification in NeuroImaging.
-
T. Moreau
- Master Data Science (IPP/UP Saclay): Datacamp.
-
B.Thirion
- MVA Master (École Polytechnique, École Normale Superiore, Centrale Supelec): Brain Function ; 12h
- NeuroEngineering Master (UPSaclay): fMRI data analysis; 2h
10.2.1 Supervision
-
P. Ciuciu
- Merlin Dumeur (with M. Palva, Aalto Univ), PhD in cotutelle (4y), 2020-2025 (defense in Feb 2025)
- Pierre-Antoine Comby (with A. Vignaud, CEA), PhD 2021-2025 (defense in March 2025)
- Serge Brosset, (with Z. Saghi, CEA) PhD 2022-2025
- Asma Tanabene (with C. Giliyar-Radhakrishna), PhD 2024-2027
- Caini Pan (w. A. Vignaud & C. Giliyar-Radhakrishna), PhD 2024-2027
- Caini Pan, M2, Telecom ParisTech, (Apr - Oct 2024, with C. Giliyar-Radhakrishna)
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B. Thirion
- Thomas Chapalain, PhD 2021-2025 (with E.Eger, CEA)
- Nicolas Salvy, PhD 2023-2026 (with H.Talbot, CentraleSupelec)
- Joseph Paillard, 2024-2027 (with D.Engemann, Roche)
- Angel Reyero Lobo, 2024-2027 (with P.Neuvial, CNRS)
- Sonia Mazelet, 2024-2027 (with R.Flamary, IPParis)
- Pierre-Louis Barbarant, 2024-2027 (with F.Meyniel, CEA)
- Fernanda Ponce, 2024-2027 (with D.Wassermann, Inria)
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D. Wassermann
- Alexandre Le Bris, PhD 2022-2025
- Gabriela Gomez Jimenez, PhD 2023-2026 (with J. Valette CEA)
-
T. Moreau
- J. Perdereau (with F. Vallée, APHP), PhD 2022-2025
- V. Loison (with J. Cartailler, APHP), PhD 2023-2026
- C. Eve (with G. Varoquaux, Inria), PhD 2024-2027
10.2.2 Juries
-
B. Thirion
- reviewer for Mathieu Gilson's habilitation defense on September 25th, Marseille, France
- Examiner for Julie Carlier's PhD defense on Nov 26th, Paris, France
- Examiner for Ulysse Klatzmann's PhD defense on Nov 26th, Paris, France
- Reviewer for 's PhD defense on December 15th, Sophia Antipolis, France
- Examiner for Shizhe Wu's public defense on Jan 24th, Geneva, Switzerland
10.3 Popularization
10.3.1 Participation in Live events
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February 2025
Inria interviewed Demian Wassermann in French to discuss how we will soon be able to predict thoughts.
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March 2025
Demian Wassermann gave talks at different Parisian high-schools within the Chiche! program.
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March 10, 2025
During Brain Week, Anne Legall, a science journalist at France Info, interviewed Philippe Ciuciu about the BrainSync research project; see Le billet Sciences.
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June 2025
An article was published on the Inria website about the BrainSync project led by Philipe Ciuciu, titled: Et si l’IA aidait le cerveau à réapprendre après un AVC ?
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September 2025
An interview with Philippe Ciuciu was published in the monthly specialist newspaper "Pharmaceutiques" in French, discussing how AI can help improve the care of stroke patients.
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October 2025
As deputy director of the DataIA institute, Demian Wassermann was interviewed in Big Data & AI Exhibition Paris to discuss how AI contributes to decoding the brain and opening the path to precision medicine.
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October 2025
Bertrand Thirion was invited by Café-éco des clubs Rotary from the Aube region in the eastern part of France.
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November 2025
Demian Wassermann was invited to discuss AI and sovereignty at VivaTech 2025.
11 Scientific production
11.1 Major publications
- 1 articleFunctional gradients in the human lateral prefrontal cortex revealed by a comprehensive coordinate-based meta-analysis.eLife2022HALDOI
- 2 articleImpact of B0 field imperfections correction on BOLD sensitivity in 3D‐SPARKLING fMRI data.Magnetic Resonance in MedicineDecember 2023HALDOIback to text
- 3 articleDeep language algorithms predict semantic comprehension from brain activity.Scientific ReportsSeptember 2022HALDOI
- 4 articleMRI-NUFFT: Doing non-Cartesian MRI has never been easier.Journal of Open Source Software10108April 2025, 7743HALDOI
- 5 inproceedingsA framework for bilevel optimization that enables stochastic and global variance reduction algorithms.Advances in Neural Information Processing Systems (NeurIPS)New Orleans, United StatesNovember 2022HAL
- 6 articleImproving spreading projection algorithm for rapid k‐space sampling trajectories through minimized off‐resonance effects and gridding of low frequencies.Magnetic Resonance in Medicine903May 2023, 1069-1085HALDOI
- 7 articleOptimizing full 3D SPARKLING trajectories for high-resolution T2*-weighted Magnetic Resonance Imaging.IEEE Transactions on Medical ImagingAugust 2022HAL
- 8 inproceedingsBenchopt: Reproducible, efficient and collaborative optimization benchmarks.NeurIPS 2022 - 36th Conference on Neural Information Processing SystemsNew Orleans, United StatesNovember 2022HAL
- 9 articleNC-PDNet: a Density-Compensated Unrolled Network for 2D and 3D non-Cartesian MRI Reconstruction.IEEE Transactions on Medical ImagingJanuary 2022HALDOI
- 10 articleData augmentation for learning predictive models on EEG: a systematic comparison.Journal of Neural EngineeringNovember 2022HALDOI
- 11 inproceedingsFaDIn: Fast Discretized Inference for Hawkes Processes with General Parametric Kernels.PMLRInternational Conference on Machine Learning202Honololu, Hawaii, United StatesJuly 2023, 32575-32597HAL
11.2 Publications of the year
International journals
International peer-reviewed conferences
Conferences without proceedings
Scientific book chapters
Doctoral dissertations and habilitation theses
Reports & preprints
Other scientific publications
11.3 Cited publications
- 77 inproceedings back to text
- 78 articleFaster independent component analysis by preconditioning with Hessian approximations.IEEE Trans. Signal Process.66152018, 4040-4049back to text
- 79 inproceedingsLearning Step Sizes for Unfolded Sparse Coding.Advances in Neural Information Processing Systems (NeurIPS)Vancouver, BC, Canada2019, 13100--13110back to textback to text
- 80 inproceedingsSuper-Efficiency of Automatic Differentiation for Functions Defined as a Minimum.International Conference on Machine Learning (ICML)July 2020back to text
- 81 inproceedingsValidating Causal Inference Models via Influence Functions.Proceedings of the 36th International Conference on Machine Learning97Proceedings of Machine Learning ResearchLong Beach, California, USAPMLR09--15 Jun 2019, 191--201URL: http://proceedings.mlr.press/v97/alaa19a.htmlback to text
- 82 articleExpressive Languages for Querying the Semantic Web.ACM Transactions on Database Systems433November 2018, 1--45DOIback to text
- 83 articleThe State of Applied Econometrics - Causality and Policy Evaluation.ArXiv e-printsJuly 2016, arXiv:1607.00699back to text
- 84 inproceedingsFeature Grouping as a Stochastic Regularizer for High-Dimensional Structured Data.ICML2019, 385--394back to text
- 85 articleDeclarative Probabilistic Programming with Datalog.ACM Transactions on Database Systems424October 2017, 1-35DOIback to text
- 86 articleMultimodal Machine Learning: A Survey and Taxonomy.IEEE Transactions on Pattern Analysis and Machine Intelligence412Feb 2019, 423-443DOIback to textback to text
- 87 articleUncovering the structure of clinical EEG signals with self-supervised learning.Journal of Neural Engineering2020back to text
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- 89 articleRepresentation learning: A review and new perspectives.Pattern Analysis and Machine Intelligence352013, 1798back to text
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