Auditory Corticothalamic Neurons are Recruited by Motor Preparatory Inputs

Abstract

SUMMARY During active sensing, neural responses to sensory inputs directly generated by our own movements are suppressed. In the auditory cortex (ACtx), self-initiated movements elicit corollary discharge from secondary motor cortex (M2) that suppresses pyramidal neuron (PyrN) spiking via recruitment of local inhibitory neurons. Here, we observed that ACtx layer (L)6 PyrNs were also activated hundreds of milliseconds prior to movement onset, at approximately the same time as fast spiking inhibitory neurons. Most L6 PyrNs were corticothalamic (CT) cells, which all expressed FoxP2, a protein marker enriched in brain areas that integrate sensory inputs to control vocal motor behaviors. L6 CTs were strongly activated prior to orofacial movements, but not locomotion, and received ten times more direct inputs from the basal ganglia than M2. These findings identify new pathways and local circuits for motor modulation of sound processing and suggest a new role for CT neurons in active sensing.

Pupillometry as a reliable metric of auditory detection and discrimination across diverse stimulus paradigms in animal models

“…Thus, to avoid confounding stimulus-evoked and motion-related pupil dilation, stimuli that were presented within 7 s of a motion event were discarded from further analyses (see Methods). Note that while our piezo sensor-based motion detection picked up postural shifts and limb movements, we did not detect orofacial movements (whisking, licking, or chewing) that are also associated with PD changes [34]. Thus, it is possible that some stimulus-driven pupil responses also contain some of these motion-related PD changes.…”

Sensory Neurobiology: A New Crossroads Deep in the Cortex

“…This result raises several questions. More work is needed to determine if indeed the GPe inputs to L6 CT cells carry the pre-lick ramping activity and contribute to the peri-lick suppression observed by Clayton et al 4 . In addition, it will be exciting to determine the broader functional role of pallidal-cortical projecting neurons, including the movements and contexts that activate or inactive them.…”

“…What about other movements? To answer this question, Clayton et al devised a clever behavioral paradigm in mice, focused on licking 4 . Head-fixed mice were free to lick at a spout in front of their face.…”

“…Indeed, that is exactly what they found. Recording electrically across all 6 layers of auditory cortex, responses to the FM sweeps were reduced compared to unpredictable presentation of the same sweeps 4 .…”

“…Although the primary function of lick bouts is to collect liquid nourishment, they too have an unintended sensory consequence: selfgenerated sound. A new study by Clayton et al reported in a recent issue of Current Biology reveals a neural circuit substrate for the suppression of cortical sound responses during licking 4 . Their circuit sits at the crossroads of an unexpected anatomical pathway to the leastunderstood layer of cortex, and involves a mysterious molecule central to human speech processing.…”