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## Section: New Results

### Mapping cognitive ontologies to and from the brain

Participants : Gaël Varoquaux [Correspondant] , Bertrand Thirion, Yannick Schwartz.

Imaging neuroscience links brain activation maps to behavior and cognition via correlational studies. Due to the nature of the individual experiments, based on eliciting neural response from a small number of stimuli, this link is incomplete, and unidirectional from the causal point of view. To come to conclusions on the function implied by the activation of brain regions, it is necessary to combine a wide exploration of the various brain functions and some inversion of the statistical inference. Here we introduce a methodology for accumulating knowledge towards a bidirectional link between observed brain activity and the corresponding function. We rely on a large corpus of imaging studies and a predictive engine. Technically, the challenges are to find commonality between the studies without denaturing the richness of the corpus. The key elements that we contribute are labeling the tasks performed with a cognitive ontology, and modeling the long tail of rare paradigms in the corpus. To our knowledge, our approach is the first demonstration of predicting the cognitive content of completely new brain images. To that end, we propose a method that predicts the experimental paradigms across different studies (see Fig. 5 ).

More details can be found in [63] .

Figure 5. Maps for the forward inference (left) and the reverse inference (right) for each term category. To minimize clutter, we set the outline so as to encompass 5% of the voxels in the brain on each figure, thus highlighting only the salient features of the maps. In reverse inference, to reduce the visual effect of the parcellation, maps were smoothed using a $\sigma$ of 1.5 voxel.