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Conference Papers Year : 2013

Identifying predictive regions from fMRI with TV-L1 prior


Decoding, i.e. predicting stimulus related quantities from functional brain images, is a powerful tool to demonstrate differences between brain activity across conditions. However, unlike standard brain mapping, it offers no guaranties on the localization of this information. Here, we consider decoding as a statistical estimation problem and show that injecting a spatial segmentation prior leads to unmatched performance in recovering predictive regions. Specifically, we use L1 penalization to set voxels to zero and Total-Variation (TV) penalization to segment regions. Our contribution is two-fold. On the one hand, we show via extensive experiments that, amongst a large selection of decoding and brain-mapping strategies, TV+L1 leads to best region recovery. On the other hand, we consider implementation issues related to this estimator. To tackle efficiently this joint prediction-segmentation problem we introduce a fast optimization algorithm based on a primal-dual approach. We also tackle automatic setting of hyper-parameters and fast computation of image operation on the irregular masks that arise in brain imaging.
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hal-00839984 , version 1 (01-07-2013)


  • HAL Id : hal-00839984 , version 1


Alexandre Gramfort, Bertrand Thirion, Gaël Varoquaux. Identifying predictive regions from fMRI with TV-L1 prior. Pattern Recognition in Neuroimaging (PRNI), Jun 2013, Philadelphia, United States. ⟨hal-00839984⟩
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