Beyond Body Maps: Information Content of Specific Body Parts is Distributed Across the Somatosensory Homunculus

Abstract

The homunculus in primary somatosensory cortex (S1) is famous for its body-part selectivity, but this dominant feature may eclipse other representational features, e.g., information content, also relevant for S1 organisation. Using multivariate fMRI analysis, we asked whether body-part information content can be identified in S1 beyond its primary area. Throughout S1, we identified significant representational dissimilarities between body parts, but also subparts, in distant non-primary areas (e.g., between the hand and the lips in the foot area, between different face parts in the foot area). Two movements performed by one body part (e.g., the hand) could also be dissociated well beyond its primary area (e.g., in the foot and face areas), even within Brodmann area 3b. Our results demonstrate that information content is more distributed across S1 than previously considered. This finding reveals yet unexplored underlying information contents in S1 that could be harnessed for rehabilitation and brain-machine interfaces.