Contributions of the motor cortex and cerebellum during skilled and adapted forelimb reaching

Abstract

Motor adaptation is a form of sensorimotor learning, whereby motor actions are continually updated to adapt to sensory perturbations, enabling us to maintain accurate movements. Both the motor cortex and the cerebellum play crucial roles in the control of skilled movements. Human imaging studies have shown connections between the cerebellum and motor cortex are modulated during motor learning, and perturbation related activity changes have been observed in both regions.

The aim of this work was to explore the roles of the motor cortex and the anterior interpositus of the cerebellum and their interaction during motor adaptation. To do this, a behavioural task was developed specifically for unrestrained rats in combination with chronic neural recordings. Animals displayed behaviour consistent with characteristics of motor adaptation during their first experience of the perturbation, including an aftereffect once the perturbation was removed.

During sessions without the perturbation, task related neural activity was observed both in the cerebellum and motor cortex during each phase of the reaching movement. Neurons in the anterior interpositus also displayed high firing rates associated with small changes in velocity during the acceleration phase of the pull. Differences in activity between successful and unsuccessful pulls were also observed in both brain regions.

Perturbation related activity in the cerebellum was found, which persisted once the perturbation was removed (‘memory’ related activity). Changes in activity during the perturbation were also seen in the motor cortex; this change likely reflects altered movement dynamics due to the perturbation, with memory related activity emerging in subsequent perturbation sessions.
Models of motor adaptation have largely focused on the cerebellum, however these data suggest they may benefit from the inclusion of the motor cortex, potentially for long term savings, as well as providing movement dynamics information.

Date of Award	21 Jan 2021
Original language	English
Awarding Institution	University of Bristol
Supervisor	Richard Apps (Supervisor), Nadia L Cerminara (Supervisor) & Martin J Pearson (Supervisor)