LAUSR

Motor learning is a fundamental skill in everyday life. Acquisition of new motor skills engage cortico-striatal-cerebellar connectivity. Particularly patients with Parkinson”s disease and spinocerebellar ataxia are affected but these patient groups fundamentally differ in their behaviour in implicit motor learning tasks. Yet little is known about motor learning in relation to rule-based motor sequence learning. The aim of the current study was to test whether there are differences or similarities in implicit and explicit motor learning tasks in PD, SCA and healthy controls. Eye movements were recorded in 22 patients with Parkinson”s disease (PD), 20 patients with spinocerebellar ataxia (SCA) and 20 age-matched healthy control subjects. The subjects had to perform an implicit motor learning task (two runs of saccade adaptation) and an explicit motor learning task with an implicit sequence-learning paradigm. Healthy subjects were able to adapt in both runs and stored the adapted gain between the sessions. PD patients were able to adapt to the transient displacement of the target but did not store the information between the two learning sessions. Patients with SCA did not adapt in the first run but in the second run. In the explicit motor learning task, all participants showed a general motor learning. Patients performed better in the implicit learning trials but needed twice the time of healthy participants. We conclude that PD patients are not impaired in learning the implicit motor adaptation task. However, their storage of motor learning is selectively impaired possibly due to reduced functioning of cortico-striatal-cerebellar loops and their connections to motor memory systems. SCA patients, in contrast, lack implicit saccade learning because the cerebellum is crucially involved in saccade adaptation. Interestingly, they show a moderate storage of the adapted saccade gain form the first to the second learning session. This might suggest that SCA patients can still use storage signals of the cortico-striatal-cerebellar network.