Motor learning in stroke : imaging training induced plasticity

Stroke is a leading cause of death and disability in Western countries and it is estimated that up to 70% of stroke survivors have a long-lasting disability of the upper limb. The purpose of this study was to examine plasticity at the neuronal level to distinguish between recovery and compensation and how this relates to recovery of arm movement at the behavioural and functional levels in five chronic stroke patients. Brain activation patterns associated with a pointing movement involving the whole arm were identified over two baselines and one post-training intervention evaluation. At each evaluation, a clinical physical and cognitive evaluation, and a recording of the movement kinematics was performed. Analysis was performed on three regions of interest (ROI) bilaterally; primary motor cortices (M1), premotor cortices (PMC) and the primary sensorimotor cortices (S1). A measure of signal intensity, the location of peak activation, and a measure of the contribution of each hemisphere in the ROIs was examined on a case-by-case basis. We found a trend for increased contralesional involvement, changes in signal strength in each ROI and shifts in the peak activation in many directions, which paralleled increases in motor functioning. Our results seem to suggest that contralesional involvement in our ROIs may be sustaining recovery in these patients, and we can confirm that the more the activation in the stroke brain returns to the activation seen in healthy individuals, the better the recovery. Although it is possible that an absolute distinction between recovery and compensation at the neuronal level cannot be made, our results show that recovery at the behavioural and functional levels are accompanied by changes in brain activity. A relationship must be determined if we are to venture into using fMRI as a tool to influence clinical decisions during recovery from stroke