| Abstract: | A well-developed descending efferent system of the caudate nucleus has been revealed by retrograde axonal transport of horseradish peroxidase. It consists of numerous projections into the thalamus. A topical differentiation of the connections between the caudate nucleus and the paleostriatum and substantia nigra was found. It was established that the main source of efferent connections of the caudate nucleus were small and medium-sized neurons. It was demonstrated that the subthalamic nucleus has a special role in the descending efferent system of the caudate nucleus. In addition to the direct connections into the caudate nucleus itself the subthalamic nucleus has direct connections with the main output structures of the caudate nucleus, the paleostriatum, and the substantia nigra. The concept that the descending and ascending connections are interlinked in the mammalian central nervous system is supported by the results of this investigation into the caudate nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 509–517, July–August, 1985. |
