Topical Review : The Cerebellum: It's About Time! But Timing Is Not Everything-New Insights Into the Role of the Cerebellum in Timing Motor and Cognitive Tasks

Converging evidence from different research studies supports a role for the cerebellum in timing neural processes. The cerebellum is part of a distributed system for motor control. The timing hypothesis provides a specific functional role for the unique contribution of the cerebellum. The timing capabilities of the cerebellum appear to extend beyond motor control into tasks focusing on perceptual processing that require the precise representation of temporal information and sensorimotor learning. Behavioral and modeling studies suggest that the cerebellar timing system is best characterized as providing a near-infinite set of interval-type timers rather than as a single clock with pacemaker or oscillatory properties, but this is controversial. In addition to learning precisely timed motor responses, the cerebellum is involved in on-line processing using feed-forward systems for which sensory input is used prior to movement execution to improve movement accuracy. This would be a mechanism for triggering accurate "time." The cerebellum continues to fascinate scientists, and although survival is possible without the cerebellum, the resultant quality of life is significantly compromised with clumsiness, ataxia, hypotonia, dysarthria, slowing of various cognitive perceptual processes, and impaired fine motor and ocular-motor coordination. The last three decades have seen the development of research that has focused on how the cerebellum functions. Further neurophysiologic research in cerebellar cortical neurotransmission is likely to further our understanding of the cerebellar contribution to timing sensorimotor processes.