Plasticity of cortical motor representations duringupper limb immobilisation : implications forstroke rehabilitation and motor learning.

Abstract

Advances in the understanding of the neural plasticity occurring with motor learning and hemiparetic stroke have contributed to the development of motor rehabilitation strategies for treating poststroke upper limb hemiparesis. However, a relative drawback has been that, in general, these strategies are most compatible with the recovery profiles of relatively high-functioning stroke survivors and therefore do not easily translate into benefit to those individuals sustaining low-functioning upper limb hemiparesis, who otherwise have poorer residual motor function. For these individuals, alternative motor rehabilitation strategies are currently needed (Chapter 1). Chapter 2 reviews several upper limb immobilisation (ULI) studies that have been conducted with humans and animals. Then, it discusses how their findings could inspire the creation of a neural plasticity model that is likely to be of great relevance to the contexts of motor rehabilitation after stroke and motor learning. For instance, such model could contribute to the development of alternative motor rehabilitation strategies for treating poststroke upper limb hemiparesis and to enhancing motor learning in humans. Chapter 3 outlines the research questions addressed in this Thesis. Chapter 4 describes the methods and results of two studies (Studies 1 and 2) which, respectively, assessed the test-retest reliability and characterised the learning of a computer-based motor task designed to be used in futures studies in combination with an immobilisation protocol. Chapter 5 describes the method of transcranial magnetic stimulation (TMS), which was used in another study (Study 3) that makes up this Thesis. Chapter 6 briefly outlines the outcomes of a pilot study performed to optimise the methods for Study 3. In the latter, TMS was used to assess changes in motor cortex/corticospinal excitability during a protocol of 9 hours of ULI (Chapter 7). Chapter 8 discusses the results from Studies 1, 2 and 3, and Chapter 9 provides a conclusion with the implications of the present findings. Chapter 10 summarises the novelties from this Thesis.