An Experimental-Anatomical Study on the Cortical Projections of the Pulvinar Nuclear Group of the Thalamus in the Cat

Localized stereotaxic lesions were placed in the pulvinar nuclear group of the thalamus, viz., the medial, lateral and inferior pulvinar nuclei and the suprageniculate nucleus, and the ensuing fiber degeneration was traced to the cerebral cortex by the method of Nauta and Gygax (1954). Following lesions of the medial pulvinar nucleus, cortical degeneration is found diffusely in the middle and posterior portions of the lower bank and fundus of the middle suprasylvian sulcus and the adjacent part of the posterior ectosylvian gyrus as well as in the posterior bank of the posterior suprasylvian sulcus. However, the severely degenerated portion in these cortical areas varies with the site of the lesion in the medial pulvinar nucleus. In the heavy cortical projection of this nucleus, there appears to be a reversal in the anteroposterior dimension; the rostral part of the nucleus projecting to the posterior portion of the inferior bank of the middle suprasylvian sulcus and the adjacent part of the posterior ectosylvian gyrus, and the caudal part projecting more rostrally in these cortical areas. In cases with lesions in the ventral part of the medial pulvinar nucleus, light degeneration is found in the anterior sylvian gyrus. The lesions in the lateral pulvinar nucleus produce cortical degeneration in the middle and posterior suprasylvian gyri with its lateral sulcal wall and in the zone of confluence of the posterolateral and posterior suprasylvian gyri. Severe degeneration is, however, confined to the middle suprasylvian gyrus and the zone of confluence of the posterolateral and posterior suprasylvian gyri. Scarcely any degeneration is found in area 19 in the lateral cortex in most of our cases with lesions in the lateral pulvinar nucleus, but scattered degeneration is seen in the medial cortex around the splenial sulcus, including area 19. There appears to be an anteroposterior organization in the heavy cortical projection of the lateral pulvinar nucleus. After lesions in the inferior pulvinar nucleus, degeneration is seen in the medial (area 19) and lateral banks of the lateral sulcus and the upper bank of the middle suprasylvian sulcus. In addition, light degeneration is found in parts of area 18 and the crown of the suprasylvian gyrus. The lesions of the suprageniculate nucleus lead degeneration to the cortex around the anterior half of the middle suprasylvian sulcus and in the anterior sylvian gyrus and the adjacent posterior bank of the anterior ectosylvian sulcus. The suprageniculate nucleus appears to project to these cortical regions in a topical manner in the anteroposterior dimension.