Abstract
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-related, motor-related, and choice-related activities in whisker primary somatosensory cortex (S1), whisker region of 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.
Highlights
To accomplish goal-directed behavior, the brain selects task-relevant stimuli and outputs the appropriate motor responses
This was studied in a whisker detection task, in which mice were trained to respond to passive whisker deflections by licking a central lickport
Our recordings within the neocortex focused on three regions which have been identified in a recent calcium imaging study (Aruljothi et al, 2020) as potentially contributing to the transformation
Summary
To accomplish goal-directed behavior, the brain selects task-relevant stimuli and outputs the appropriate motor responses. A crucial component of this process is the transformation of an internal representation of a sensory stimulus into an internal representation of a motor. Received January 6, 2021; accepted January 8, 2021; First published January 25, 2021. The authors declare no competing financial interests. Identifying where this occurs is an essential first step in developing mechanistic understandings of this process. Correlates of sensory-motor transformations in neocortex have been identified in non-human primates (Kim and Shadlen, 1999; Shadlen and Newsome, 2001; de Lafuente and Romo, 2006; Siegel et al, 2015).
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