Roles of the cerebellum and basal ganglia in temporal integration: insights gained from the synchronized tapping task

The aim of this study was to clarify the roles of the cerebellum and basal ganglia for temporal integration. We studied 39 patients with spinocerebellar ataxia (SCA), comprising SCA6, SCA31, Machado–Joseph disease (MJD, also called SCA3), and multiple system atrophy (MSA). Thirteen normal subjects participated as controls. Participants were instructed to tap on a button in synchrony with isochronous tones. We analyzed the inter-tap interval (ITI), synchronizing tapping error (STE), negative asynchrony, and proportion of delayed tapping as indicators of tapping performance. The ITI coefficient of variation was increased only in MSA patients. The standard variation of STE was larger in SCA patients than in normal subjects, especially for MSA. Negative asynchrony, which is a tendency to tap the button before the tones, was prominent in SCA6 and MSA patients, with possible basal ganglia involvement. SCA31 patients exhibited normal to supranormal performance in terms of variability STE, which was surprising. In conclusion, cerebellar patients generally showed greater STE variability, except for SCA31. The pace of tapping was affected in patients with possible basal ganglia pathology. Our results suggest that interaction between the cerebellum and the basal ganglia is essential for temporal processing. The cerebellum and basal ganglia together with their interaction regulates synchronized tapping, resulting in distinct tapping patterns among different SCA subtypes.