Exploring early corticomotor reorganisation

Abstract

The overarching aim of this thesis was to enhance our understanding of early corticomotor reorganisation in response to novel stimuli (motor skill training and acute pain). To achieve this aim, four primary studies (Chapters 2-5) were conducted and published. Study 1 (Chapter 2) explored the within- and between-session reliability of corticomotor outcomes assessed using rapid TMS mapping (map area, volume, centre of gravity, discrete peaks in corticomotor excitability, and mean motor evoked potential). This study also assessed the validity of rapid mapping by testing its equivalence with traditional mapping methods. Study 2 (Chapter 3) used rapid mapping to investigate corticomotor reorganisation during short-term motor skill learning in thirty individuals. This study demonstrated, for the first time, that reorganisation of lower back muscle representations occurs rapidly (within minutes) in certain individuals. Study 3 (Chapter 4) explored the temporal profile and variability of corticomotor reorganisation in response to acute experimental pain. Findings of this study suggest that early corticomotor responses could be used as an index to predict symptom severity. This could have utility in stratifying individuals according to their likelihood of increased or persistent pain and the development of targeted management strategies. Study 4 (Chapter 5) investigated this possibility using repeated intramuscular injection of nerve growth factor, a novel and clinically-relevant model of musculoskeletal pain. The findings of this study suggest that early rTMS over M1 may expedite recovery following acute musculoskeletal pain or injury. Taken together, this thesis makes a substantial and original contribution to our understanding of neuroplasticity. By evaluating rapid TMS mapping, early corticomotor reorganisation can now be assessed validly and reliably, allowing exploration of early drivers of nervous system plasticity. Decreasing map acquisition times may also increase the utility of TMS beyond research settings, potentially allowing corticomotor reorganisation to be assessed in clinical environments. The experimental studies throughout this thesis provide valuable insight into the temporal profile and modifiability of early corticomotor reorganisation. This work highlights the prognostic and therapeutic utility of exploring early corticomotor reorganisation and the need for further research in this area.

Date of Award	2022
Original language	English