Abstract

In the cat, the cerebellum projects via the ventroanterior-ventrolateral (VA-VL complex of the thalamus to the motor and premotor cortices and also to the panetal association cortex. Cerebellar inputs to each of these regions have been characterized electrophysiologically by depth profiles of cortical potentials following stimulation of the brachium conjunctivum and of the VA-VL complex, and morphologically by the laminar dis tribution of thalamocortical (TC) terminations, in aggregate and at the single-axon level. One population of TC neurons terminated mainly in layer I and was as sociated with late surface negative potentials. A second population, with terminations in layers III and IV, was associated with early deep negative potentials. Termi nations in layer III of the motor cortex formed multiple patches about 1–1.5 mm wide (mediolateral), which aligned to form 2–5 mm stripes extended rostrocaudally. This pattern correlates with the configuration of individual IC axons, which have two to six separate terminal patches distributed over 6 mm (rostrocaudal). The wide morphological divergence of single TC axons in the cor tex may imply functionally multiple innervation of different efferent columns. Alternately, along with other inputs, it may permit a highly dynamic output selection from multiple representations, for example, of a variety of muscle groups in different combinations.

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