Motor learning in Parkinson's disease: limitations and potential for rehabilitation.

The striatum is very much involved in learning motor sequences particularly in the consolidation phase, predicting that motor learning is affected in Parkinson's disease (PD). We conducted a literature review on this question and showed that behavioural studies indicate a relatively preserved acquisition as well as retention of motor learning in PD. Persons with PD did demonstrate slower learning-rates than controls. Brain imaging studies highlighted that much more brain activity is needed and different neural networks are recruited in PD, suggesting a reduced efficiency of learning. Using additional sensory information may optimize motor learning in PD. There is abundant evidence that cueing helps to achieve better movement performance and that these effects are retained immediately after withdrawal, possibly indicating the first signs of consolidation. Also, automatization of cued learning was demonstrated, as cues not only enhanced dual-task performance but these increments were retained after cue withdrawal. However, the effect of longer periods of cued training on retention of cued and uncued performance is not well established and some studies suggest that learning effects may be cue-dependent. The results of this review support the notion that adopting motor learning principles could benefit rehabilitation in PD. Even so, the limitations of reduced flexibility, efficiency and increased context-specificity of motor learning in PD need to be taken into account.