Topographical arrangement of thalamocortical neurons in the centrolateral nucleus (CL) of the cat, with special reference to a spino-thalamo-motor cortical path through the CL.

In the centrolateral nucleus of the thalamus (CL) in the cat, a topographical arrangement of the thalamocortical projection neurons was demonstrated by utilizing retrograde axonal transport of horseradish peroxidase (HRP). Following injections of HRP into the medial or lateral areas of the anterior sigmoid gyrus (ASG), HRP-labeled neurons were located medially or laterally in the caudal levels of the CL, respectively; neurons in the central areas of the CL were labeled after injections of HRP into the rostral areas of the middle suprasylvian or the lateral gyrus. It was also shown by means of the combined HRP and Fink-Heimer method (Blomqvist and Westman, 1975) that the spinothalamic fibers terminated around CL neurons which were labeled with HRP injected into the lateral areas of the ASG. Hence, the caudolateral aspects of the CL were considered to represent a relay of the spino-thalamo-motor cortical paths.