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Some ascending connections of the pulvinar and nucleus lateralis posterior of the thalamus in the cat

1972; Elsevier BV; Volume: 44; Issue: 1 Linguagem: Inglês

10.1016/0006-8993(72)90369-1

1872-6240

Ann M. Graybiel,

Primate Behavior and Ecology

The thalamocortical projections of the pulvinar and nucleus lateralis posterior (LP) have been identified in the cat by the use of modified Nauta and Fink-Heimer techniques. Electrolytic lesions of various size were placed within the thalamus by means of stereotaxic approaches designed to avoid damage to the neocortex, its thalamic peduncles and its callosal afferents. Lesions centered in LP, but usually invading the suprageniculate nucleus as well, elicit dense fiber degeneration in the largely hidden cortex of the lateral, suprasylvian and anterior ectosylvian sulci, and to a lesserf extent within the splenial sulcus. In 3 further zones, viz., the anterior sylvian gyrus, the zone of confluence of the posterior lateral and posterior suprasylvian gyri, and parts of parietal areas 5 and 7, major fields of degeneration lie within exposed gyral surfaces. Lesions confined to the suprageniculate nucleus elicit fiber degeneration largely restricted to the anterior sylvian gyrus. Together these thalamocortical projections show a marked tendency to involve rim-areas alongside, but not within, the major sensory areas of the neocortex. At subcortical levels, degenerating fibers can be traced to discrete subdivisions of the caudoputamen and basolateral amygdala. By contrast, the thalamocortical degenerations traced from lesions centered in the pulvinar and nucleus lateralis intermedius (LI) largely spare these rim-areas, concentrating instead along the crown and medial shoulder of the suprasylvian gyrus and to a lesser extent extent within the splenial sulcus. The pulvinar, as traditionally defined, appears to project primarily to the posterior limb of the suprasylvian gyrus, LI to the adjoining middle length of this gyrus. These findings suggest that the posterior association cortex of the cat's hemisphere may be divided into proximal association cortex, including circumsensory rim-areas, and distal association cortex comprising much of the crown of the suprasylvian gyrus.