Frequency selective encoding of substrate vibrations in the somatosensory cortex

Abstract

Sensing vibrations that propagate through solid substrates conveys fundamental information about moving objects and other nearby dynamic events. Here we report that neurons responsive to substrate vibrations applied to the mouse forelimb reveal a new way of representing frequency information in the primary somatosensory cortex (S1). In contrast to vibrotactile stimulation of primate glabrous skin, which produces temporally entrained spiking and frequency independent firing rates, we found that mouse S1 neurons rely on a different coding scheme: their spike rates are conspicuously tuned to a preferred frequency of the stimulus. Histology, peripheral nerve block and optogenetic tagging experiments furthermore reveal that these responses are associated with the activation of mechanoreceptors located in deep subdermal tissue of the distal forelimb. We conclude that the encoding of frequency information of substrate-borne vibrations in the mouse S1 might be analogous to the representation of pitch of airborne sound in auditory cortex.