Oscillatory activity in the basal ganglia.

The exact mechanisms underlying the dysfunction of the basal ganglia (BG) that leads to movement disorders such as Parkinson's disease (PD) and dystonia still remain unclear. The classic model, based on two distinct pathways and described nearly 20 years ago by Albin and Delong, fails to explain why lesion or stimulation of the globus pallidus interna improves dyskinesias and why lesion or stimulation of the thalamus does not cause prominent bradykinesia. These paradoxes, initially highlighted out by Marsden and Obeso, led to the proposition that the pattern of neuronal discharge determines pathological function. Accordingly, over the past decade, attention has switched from considerations of discharge rate to the characterisation of synchronised activity within BG networks. Here we would like to briefly review current knowledge about synchronised oscillatory activity in the BG and focus on its relationship to abnormal motor function. In particular, we hypothesise that the frequency of synchronisation helps determine the nature of any motor deficit, perhaps as a consequence of the different tuning properties of basal ganglia-cortical sub-circuits.