Abstract
Background
Motor skill learning (MSL) is the persistent increase in performance of a skill obtained through practice. This process is associated with changes throughout the central nervous system. One of these is a change in corticospinal excitability (CSE) assessable with Transcranial Magnetic Stimulation. Prior work has demonstrated such a change to very different extents with and without causally linking it to the improvements in motor performance.
Objectives
The aim of this PhD project has been to explore the relation between changes in CSE and motor performance over the time course of learning a novel visuomotor skill. I hypothesized that changes in CSE accompanying long-term motor practice relate to the process of learning rather than repetitive practice on an acquired skill and investigated this by incrementally increasing task difficulty and thus postponing saturation of learning. Furthermore, we aimed to
investigate the feasibility of applying paired associative stimulation to the investigation of learning-dependent motor cortical plasticity by comparing the transient increase in CSE accompanying motor skill learning to the associative
plasticity induced by pairing electrical motor point stimulation and magnetic stimulation in the same population.
Results
Six weeks of visuomotor practice with increasing task difficulty led to superior performance on a ‘skilled’ task level and equal performance on start-out task level. Correlated to this prolonged increases in CSE to the trained hand was
observed. Additionally, intermanual transfer of the learning and coinciding increases in ipsilateral CSE was superior following progressive training. A shorter duration of training (4 days) with a similar progressive and non-progressive training protocol resulted in smaller but evident behavioural differences. Accompanying this only progressive practice caused within-session increases in CSE after the first day of practice. No relation was found between the behavioural and electrophysiological changes. Finally, plastic changes following a high success-rate motor point paired associative stimulation protocol did not predict those associated with one session of motor skill learning. The latter showed no significant relation to changes in performance.
Conclusions and perspectives
The findings from study 1 and 2 emphasize the importance of individually adjusting the task difficulty to maximize motor outcome and boost plastic changes associated with long-term motor practice and rehabilitation. Whereas longterm changes in CSE associated with several weeks of training probably reflect changes underlying the improvement in visuomotor control, within-session increases in CSE reflect processes related to acquisition of a novel visuomotor skill and not level of performance or the increases in performances. Changes in CSE can be induced by repeatedly pairing peripheral and central stimulations, but these changes are unrelated to those accompanying motor skill learning. In brief, the results of the present thesis confirm previous findings demonstrating increases in CSE associated with weeks of motor practice and elaborates that these are related to the process of learning as revealed by prolonged increases associated with the progressive practice. In contrast, within-session changes in CSE are unrelated to changes in behaviour and may simply be a marker for upstream processes related to motor skill learning.
Motor skill learning (MSL) is the persistent increase in performance of a skill obtained through practice. This process is associated with changes throughout the central nervous system. One of these is a change in corticospinal excitability (CSE) assessable with Transcranial Magnetic Stimulation. Prior work has demonstrated such a change to very different extents with and without causally linking it to the improvements in motor performance.
Objectives
The aim of this PhD project has been to explore the relation between changes in CSE and motor performance over the time course of learning a novel visuomotor skill. I hypothesized that changes in CSE accompanying long-term motor practice relate to the process of learning rather than repetitive practice on an acquired skill and investigated this by incrementally increasing task difficulty and thus postponing saturation of learning. Furthermore, we aimed to
investigate the feasibility of applying paired associative stimulation to the investigation of learning-dependent motor cortical plasticity by comparing the transient increase in CSE accompanying motor skill learning to the associative
plasticity induced by pairing electrical motor point stimulation and magnetic stimulation in the same population.
Results
Six weeks of visuomotor practice with increasing task difficulty led to superior performance on a ‘skilled’ task level and equal performance on start-out task level. Correlated to this prolonged increases in CSE to the trained hand was
observed. Additionally, intermanual transfer of the learning and coinciding increases in ipsilateral CSE was superior following progressive training. A shorter duration of training (4 days) with a similar progressive and non-progressive training protocol resulted in smaller but evident behavioural differences. Accompanying this only progressive practice caused within-session increases in CSE after the first day of practice. No relation was found between the behavioural and electrophysiological changes. Finally, plastic changes following a high success-rate motor point paired associative stimulation protocol did not predict those associated with one session of motor skill learning. The latter showed no significant relation to changes in performance.
Conclusions and perspectives
The findings from study 1 and 2 emphasize the importance of individually adjusting the task difficulty to maximize motor outcome and boost plastic changes associated with long-term motor practice and rehabilitation. Whereas longterm changes in CSE associated with several weeks of training probably reflect changes underlying the improvement in visuomotor control, within-session increases in CSE reflect processes related to acquisition of a novel visuomotor skill and not level of performance or the increases in performances. Changes in CSE can be induced by repeatedly pairing peripheral and central stimulations, but these changes are unrelated to those accompanying motor skill learning. In brief, the results of the present thesis confirm previous findings demonstrating increases in CSE associated with weeks of motor practice and elaborates that these are related to the process of learning as revealed by prolonged increases associated with the progressive practice. In contrast, within-session changes in CSE are unrelated to changes in behaviour and may simply be a marker for upstream processes related to motor skill learning.
| Originalsprog | Engelsk |
|---|
| Udgivelsessted | Copenhagen |
|---|---|
| Forlag | Department of Nutrition, Exercise and Sports, Faculty of Sciences, University of Copenhagen |
| Antal sider | 164 |
| ISBN (Trykt) | 978-87-7311-946-1 |
| Status | Udgivet - 2015 |