Movement Initiation Signals in Mouse Whisker Motor Cortex

Summary

Frontal cortex plays a central role in the control of voluntary movements, which are typically guided by sensory input. Here, we investigate the function of mouse whisker primary motor cortex (wM1), a frontal region defined by dense innervation from whisker primary somatosensory cortex (wS1). Optogenetic stimulation of wM1 evokes rhythmic whisker protraction (whisking), whereas optogenetic inactivation of wM1 suppresses initiation of whisking. Whole-cell membrane potential recordings and silicon probe recordings of action potentials reveal layer-specific neuronal activity in wM1 at movement initiation, and encoding of fast and slow parameters of movements during whisking. Interestingly, optogenetic inactivation of wS1 caused hyperpolarization and reduced firing in wM1, together with reduced whisking. Optogenetic stimulation of wS1 drove activity in wM1 with complex dynamics, as well as evoking long-latency, wM1-dependent whisking. Our results advance understanding of a well-defined frontal region and point to an important role for sensory input in controlling motor cortex.

Highlights

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  Optogenetic excitation (inactivation) of wM1 evokes (inhibits) whisking

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  Layer-specific neuronal activity in wM1 encodes onset, phase, and envelop of whisking

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  Optogenetic inactivation of sensory cortex decreases wM1 activity and whisking

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  Optogenetic excitation of sensory cortex initiates whisking dependent upon wM1

Abstract

Sreenivasan, Esmaeili et al. delineate layer-specific neuronal activity patterns in mouse whisker motor cortex contributing to initiation and control of exploratory whisking. In turn, whisker motor cortex and whisker movements are strongly influenced by neuronal activity in primary somatosensory cortex.