Interaction of sensorimotor signals in the rat vibrissa system

Sensory perception in natural environments involves the dual challenge to encode external stimuli and manage the influence of changes in body position that alter the sensory field. To examine mechanisms used to integrate sensory signals elicited by both external stimuli and motor activity, we trained rats to perform an active search task with a single vibrissa. We recorded neuronal activity in primary somatosensory cortex, along with vibrissa position and touch signals, as rats rhythmically swept their vibrissa in search of a target. A majority of neurons respond to touch and, critically, ̃20 % are transiently excited only when contact occurs at a cell- specific phase in the whisk cycle. This response arises from a nonlinear interaction, consistent with gating by shunting synaptic inhibition, between vibrissa touch and a motion-derived signal that dynamically labels each neuron with a preferred phase. The observed response is likely to underlie estimation of object position in a head-centered reference frame as rodents search for vibrisso-tactile targets. More generally, our results delineate a computation that is likely to occur in all active sensorimotor system