Topographical organization of the thalamic projections to the cortex of the anterior ectosylvian sulcus in the cat.

The thalamic afferents of the anterior ectosylvian sulcal region were studied in the cat using retrograde axonal transport of horseradish peroxidase. Following peroxidase injections in the cortex of both banks and fundus of the anterior ectosylvian sulcus, retrograde labeling was always very abundant in the ventromedial thalamic nucleus, whichever part of the sulcus was injected. Consistent numbers of labeled neurons were also identified in the lateral medial subdivision of the lateral posterior-pulvinar complex, suprageniculate nucleus, posterior thalamic nuclear group and magnocellular division of the medial geniculate nucleus. A smaller number of labeled neurons was found in the ventral part of the lateral posterior nucleus, and ventralis anterior, ventralis lateralis, medialis dorsalis and intralaminar nuclei. The quantity and topographical distribution of labeled neurons in these thalamic nuclei depended on the location of the injection in the banks and fundus of the sulcus.