Cerebellum. The Basis of Cerebellar Microcircuits?

The cerebellum is a softball-sized structure located at the base of the skull. Grab the back of your head just above where it meets your neck: your hand is now cupped around your cerebellum. As with most brain systems, much of what we know about the cerebellum stems from symptoms of damage or pathology and from its connectivity with the rest of the brain. From such evidence it has long been clear that the cerebellum is an important component of the motor system. Severe abnormalities of movement are produced by pathologies of the cerebellum. Cerebellar output influences systems that are nambiguously motor, and inputs to the cerebellum convey information known to be essential for movement such as joint angles and loads on muscles. Recently it has become equally clear that the role of the cerebellum is not limited to movement. This is indicated by its interconnections with nonmotor structures; by the more subtle, nonmotor deficits seen with cerebellar lesions; and by functional imaging studies where regions of the cerebellum show activation during nonmotor tasks. A deeper understanding of the cerebellum will require dentification of the common aspects or computational demands that these motor and nonmotor functions share.