Frequency selective encoding of substrate vibrations in the somatosensory cortex

Abstract

Sensing vibrations that propagate through solid substrates conveys fundamental information about moving objects 6and other nearby dynamic events. Here we report that neurons responsive to substrate vibrations applied to the 7 mouse forelimb reveal a new way of representing frequency information in the primary somatosensory cortex (S1). In 8 contrast to vibrotactile stimulation of primate glabrous skin, which produces temporally entrained spiking and 9 frequency independent firing rates, we found that mouse S1 neurons rely on a different coding scheme: their spike 10 rates are conspicuously tuned to a preferred frequency of the stimulus. Histology, peripheral nerve block and 11optogenetic tagging experiments furthermore reveal that these responses are associated with the activation of 12 mechanoreceptors located in deep subdermal tissue of the distal forelimb. We conclude that the encoding of 13 frequency information of substrate-borne vibrations in the mouse S1 might be analogous to

Tactile sensory channels over-ruled by frequency decoding system that utilizes spike pattern regardless of receptor type

“…It is known that about 70–80% of rapidly adapting neurons in somatosensory cortex S1 show convergent inputs deriving from both afferent classes, and it may be that these neurons are responsible for this generalised frequency processing. Saal et al (2015) made an interesting observation that input from FAI afferents determines the cortical neuron response rate due to its net excitatory drive, while the more temporally-precise PC-channel has a balanced excitatory-inhibitory drive that can control the precise spike timing, which is useful in various encoding schemes (Birznieks and Vickery, 2017; Andrew Hires et al, 2015; Johansson and Birznieks, 2004; Prsa and Huber, 2018; Saal et al, 2016). This difference did not appear to affect frequency perception in the current study, as Weber fractions were found to be similar regardless of whether we used pulsatile stimuli exclusively activating FAII afferents in a time-controlled manner or used sinusoidal stimuli predominantly activating FAI afferents, presumably with less temporal precision due to the slow rising phase of the sinusoid.…”