DOES THE CEREBELLUM PROVIDE A COMMON COMPUTATION FOR DIVERSE TASKS - A TIMING HYPOTHESIS

The cerebellum provides a temporal computation for a number of tasks. We have found that the accuracy in timing motor responses is correlated across different motor effectors. Moreover, perceptual acuity in judging durations of auditory intervals is correlated with motoric measures of timing. These results suggest a common process underlying timing of different sorts, and that this process may depend on a specific neural system. Our data indicate that damage to the cerebellum impairs motor and perceptual timing. Patients with cerebellar lesions are also impaired at judging the velocity of a moving visual stimulus, a process that would appear to require precise timing. Furthermore, the lateral cerebellum has been implicated in classical "eyeblink" conditioning of the rabbit's nictitating membrane response. Because classical conditioning of discrete, adaptive responses is precisely timed, we argue that the cerebellum is the conditioning site for this response because of the need for temporal computation. Classical conditioning of responses such as of heart rate, which is not so precisely timed, does not depend on the cerebellum. The cerebellar influence on locomotion may also be one of providing temporal information. Clumsy children appear as a group to have poor timing, not only on motor production but on perception as well, as would be expected if a general computation is impaired. Because of the importance of the discovery of a cerebellar role in classical conditioning, we begin our argument with respect to classical conditioning.