Does the representation of time depend on the cerebellum? Effect of cerebellar stroke.

Behaviours that appear to depend on processing temporal information are frequently disrupted after cerebellar damage. The present study examined the role of the cerebellum in explicit timing and its relationship to other psychological processes. We hypothesized that if the cerebellum regulates timekeeping operations then cerebellar damage should disrupt the perception and the reproduction of intervals, since both are thought to be supported by a common timekeeper mechanism. Twenty-one patients with cerebellar damage from stroke and 30 normal controls performed time perception and time reproduction tasks. In the time reproduction task, timing variability was decomposed into a central timing component (clock variability) and a motor component (motor implementation variability). We found impairments only in time reproduction (increased clock variability) in patients with medial and lateral damage involving the middle- to superior-cerebellar lobules. To explore potential reasons for the temporal processing deficits, time reproduction and perception performance were correlated with independent measures of attention, working memory, sensory discrimination and processing speed. Poorer working memory correlated with increased variability in the 'clock' component of time reproduction. In contrast, processing speed correlated best with time perception. The results did not support a role for the cerebellum in timekeeping operations. Rather, deficits in timing movements may be related to a disruption in acquiring sensory and cognitive information relevant to the task, coupled with an additional impairment in the motor-output system.