Bilateral integration in somatosensory cortex is controlled by behavioral relevance.

Sensory perception requires the processing of stimuli from both sides of the body. Yet, how neurons bind stimulus information across the hemispheres to create a unified percept remains unknown. Here we perform large-scale recordings from neurons in the left and right primary somatosensory cortex (S1) in mice performing a task requiring active whisker touch to coordinate stimulus features across hemispheres. When mice touched reward-associated stimuli, their whiskers moved with greater bilateral symmetry, and synchronous spiking and enhanced spike-field coupling emerged between the hemispheres. This coordinated activity was absent in stimulus-matched naive animals, indicating that interhemispheric coupling involves a goal-directed, internal process. In S1 neurons, the addition of ipsilateral touch primarily facilitated the contralateral principal whisker response. This facilitation primarily emerged for reward-associated stimuli and was lost on trials where mice failed to respond. Silencing of callosal S1 signaling reduced bilateral facilitation and interhemispheric synchrony. These results reveal a state-dependent logic that augments the flow of tactile information through the corpus callosum.