Reshaping the Cortical Motor Map by Unmasking Latent Intracortical Connections

TLDR

The primary motor cortex is organized into medial‑to‑lateral regions that elicit contralateral limb or facial movements when stimulated. Reorganization may occur when decreased intracortical inhibition unmasks lateral excitatory connections, allowing adjacent cortical regions to expand. After peripheral nerve transection or pharmacological inhibition of cortical inhibition, stimulation of adjacent MI regions evokes movements of neighboring representations, indicating that intracortical connections and inhibitory circuits underlie cortical map reorganization.

Abstract

The primary motor cortex (MI) contains a map organized so that contralateral limb or facial movements are elicited by electrical stimulation within separate medial to lateral MI regions. Within hours of a peripheral nerve transection in adult rats, movements represented in neighboring MI areas are evoked from the cortical territory of the affected body part. One potential mechanism for reorganization is that adjacent cortical regions expand when preexisting lateral excitatory connections are unmasked by decreased intracortical inhibition. During pharmacological blockade of cortical inhibition in one part of the MI representation, movements of neighboring representations were evoked by stimulation in adjacent MI areas. These results suggest that intracortical connections form a substrate for reorganization of cortical maps and that inhibitory circuits are critically placed to maintain or readjust the form of cortical motor representations.