Thalamic afferents from the spinal cord and trigeminal nuclei. An experimental anatomical study in the rat.

Abstract

Degeneration studies after making lesions involving the spino‐thalamic pathways indicate that the projection from any level of the cord to the ventrobasal complex differs from that of the medial lemniscus in that it is less dense and ends largely in the rostral one third in a topographical pattern. Additional projections from all levels of the cord end in the nuclei pretectalis anterior, centralis lateralis, medialis dorsalis and in the medial geniculate body pars medialis and dorsal part of the posterolateral complex. Fibers from the rostral few segments of the cord, possibly from the lateral cervical nucleus, end in addition in the caudal part of the ventrobasal complex and sparsely in the parafascicular‐centrum medianum complex and zona incerta. Heavy degeneration was found in all the brains in the brainstem reticular formation. The tritgeminal sensory nuclei project heavily to the dorsomedial cell band of the ventrobasal complex and sparsely to the neighboring part of the posterolateral complex. There is no evidence of a projection from any level of the trigeminal sensory complex to any part of the intralaminar nuclei.