CORTICAL, THALAMIC, AND AMYGDALOID PROJECTIONS OF RAT TEMPORAL CORTEX

The cortical, thalamic, and amygdaloid connections of the rodent tempo ral cortices were investigated by using the anterograde transport of i ontophoretically injected biocytin. Injections into area Tel labeled a xons and terminals in the ventral regions of the dorsal and ventral su bnuclei of the medial geniculate complex, area Te3, the rostrodorsal p art of area Te2, and the ventrocaudal caudate putamen. No amygdaloid l abeling was observed. Thalamic projections from Te2 targeted the later al posterior nucleus, the dorsal part of the dorsal subnucleus of the medial geniculate complex, and the peripeduncular nucleus. Corticocort ical projections mainly terminated in the dorsal perirhinal cortex, bu t moderately dense projections were observed in medial and lateral per istriate cortex, and only light projections were observed to Tel and T e3. Projections to these isocortical regions terminated in layers I an d VI. Amygdaloid projections targeted the ventromedial subdivision of the lateral nucleus and the adjacent part of the anterior basolateral nucleus. Area Te3 was observed to project to the ventrolateral parts o f the dorsal and ventral subnuclei of the medial geniculate complex, t he dorsal perirhinal cortex, rostral Te2, and Te1. In the amygdala, la beled fibers and terminals were concentrated in the dorsolateral subdi vision of the lateral nucleus. These data confirm that areas Tel and T e3 are hierarchically organized cortical areas connected with auditory relay nuclei in the thalamus. Area Te2, in contrast, appears to be we akly connected with Tel and Te3 but is heavily connected with the peri striate cortex and tectorecipient thalamic nuclei. Te2 appears to be a visually related cortical area. The data also indicate that projectio ns from Te2 and Te3 target different subregions of the lateral nucleus and that Te2, but not Te3, projects to the basolateral nucleus. (C) 1 997 Wiley-Liss, Inc.