S1 represents multisensory contexts and somatotopic locations within and outside the bounds of the cortical homunculus

Recent literature suggests that tactile events are represented in the primary somatosensory cortex (S1) beyond its long-established topography; in addition, the extent to which S1 is modulated by vision remains unclear. To better characterize S1, human electrophysiological data were recorded during touches to the forearm or finger. Conditions included visually observed physical touches, physical touches without vision, and visual touches without physical contact. Two major findings emerge from this dataset. First, vision strongly modulates S1 area 1, but only if there is a physical element to the touch, suggesting that passive touch observation is insufficient to elicit neural responses. Second, despite recording in a putative arm area of S1, neural activity represents both arm and finger stimuli during physical touches. Arm touches are encoded more strongly and specifically, supporting the idea that S1 encodes tactile events primarily through its topographic organization but also more generally, encompassing other areas of the body.

Automated summary

Recent literature suggests that tactile events are represented in the primary somatosensory cortex (S1) beyond its topography and the modulation of S1 by vision is still unclear. To better understand S1, human electrophysiological data were recorded during touches with visual observation, physical touches without vision, and visual touches without physical contact. The findings show that vision strongly modulates S1 area 1, but only when there is a physical element involved, and neural activity in S1 represents both arm and finger stimuli during physical touches.