Cortical Localization of the Sensory-Motor Transformation in a Whisker Detection Task in Mice

Responding to a stimulus requires transforming an internal sensory representation into an internal motor representation. Where and how this sensory-motor transformation occurs is a matter of vigorous debate. Here, we trained male and female mice in a whisker detection go/no-go task in which they learned to respond (lick) following a transient whisker deflection. Using single unit recordings, we quantified sensory-, motor- and choice-related activities in whisker primary somatosensory cortex (S1), whisker primary motor cortex (wMC) and anterior lateral motor cortex (ALM), three regions that have been proposed to be critical for the sensory-motor transformation in whisker detection. We observed strong sensory encoding in S1 and wMC, with enhanced encoding in wMC, and a lack of sensory encoding in ALM. We observed strong motor encoding in all three regions, yet largest in wMC and ALM. We observed the earliest choice probability in wMC, despite earliest sensory responses in S1. Based on the criteria of having both strong sensory and motor representations and early choice probability, we identify whisker motor cortex as the cortical region most directly related to the sensory-motor transformation. Our data support a model of sensory encoding originating in S1, sensory amplification and sensory-motor transformation occurring within wMC, and motor signals emerging in ALM after the sensory-motor transformation. Significance Statement This study addresses the fundamental question of where within the neocortex a sensory stimulus representation transforms into a motor response representation during stimulus detection. We recorded and analyzed single unit activity of three cortical regions during a passive whisker detection Go/NoGo task in mice. Using quantitative assessments of sensory- motor- and choice-52 encoding across these regions, we showed that a cortical region traditionally defined as whisker motor cortex is most directly related to the transformation process. In addition, our study shows how sensory and motor signals are amplified and propagated throughout cortex. These findings open up new directions to studying the cellular and circuit mechanisms of sensory-motor transformations.

Automated summary

This study investigated where within the neocortex a sensory stimulus representation transforms into a motor response representation during stimulus detection in mice. By analyzing single unit activity in three cortical regions, it was shown that the whisker motor cortex is most directly related to this transformation process. Additionally, the study demonstrated how sensory and motor signals are amplified and propagated throughout the cortex, leading to new directions in studying sensory-motor transformations at the cellular and circuit levels.