Motor cortical plasticity in response to skill acquisition in adult monkeys

Abstract

13Cortical maps often undergo plastic changes during learning or in response to 14 injury. In sensory areas, these changes are thought to be triggered by alterations 15 in the pattern of converging inputs and a functional reassignment of the deprived 16 cortical region. In the motor cortex, training on a task that engages distal 17 effectors was shown to increase their cortical representation (as measured by 18 response to intracortical microstimulation). However, this expansion could be a 19 specific outcome of using a demanding dexterous task. We addressed this 20 question by measuring the long-term changes in cortical maps of monkeys that 21 were sequentially trained on two different tasks involving either proximal or distal 22 joints. We found that motor cortical remodeling in adult monkeys was symmetric 23 such that both distal and proximal movements can comparably alter motor maps 24 in a fully reversible manner according to task demands. Further, we found that 25 the change in mapping often included a switch between remote joints (e.g., a 26 finger site switched to a shoulder site) and reflected a usage-consistent 27 reorganization of the map rather than the local expansion of one representation 28 into nearby sites. Finally, although cortical maps were considerably affected by 29 the performed task, motor cortical neurons throughout the motor cortex were 30 equally likely to fire in a task-related manner independent of the task and/or the 31 recording site. These results may imply that in the motor system, enhanced 32 motor efficiency is achieved through a dynamical allocation of larger cortical 33 areas and not by specific recruitment of task-relevant cells. 34 Gupta et al. 2020 3 Introduction 35