[Cerebello-cerebral loop for motor control--output systems from the cerebellum to the cerebral cortex]

Input-output organization of the ventrolateral nucleus (VL) of the thalamus was analyzed electrophysiologically and morphologically at the single cell level. Virtually all pyramidal tract neurons in the motor cortex and area 6 received convergent inputs from the dentate (DN) and the interpositus (IN) nuclei and about 60% of thalamocortical (TC) neurons received convergent inputs from both the DN and the IN. Anterograde labelling following focal injection of Phaseolus vulgaris leukoagglutinin and intracellular staining of TC axons showed that the terminals in layer III tended to aggregate into patches about 1-1.5 mm wide in a frontal plane, which were arranged in longitudinal strips about 2-5 mm long in a rostrocaudal direction.