Movement-related cerebellar activation in the absence of sensory input

Movement-related cerebellar activation may be due to sensory or motor proce ssing. Ordinarily, sensory and motor processing are obligatorily linked, bu t in patients who have severe pansensory neuropathies with normal muscle st rength, motor activity occurs in isolation. In the present study, positron emission tomography and functional magnetic resonance imaging in such patie nts showed no cerebellar activation with passive movement, whereas there wa s prominent movement-related cerebellar activation despite absence of propr ioceptive or visual input. The results indicate that motor processing occur s within the cerebellum and do not support the recently advanced view that the cerebellum is primarily a sensory organ.