Topographical organization of frontal association cortex afferents originating in ventral thalamic nuclei in dog brain

Abstract

The frontal associatron cortex involves the prefrontal (PFC) and premotor (PMC) areas which are reached by projections originating in the ventral medial (VM), ventral anterior (VA) and ventral lateral (VL) thalamic nuclei. Afferents arising in particular thalamic nuclei cover various PFC-PMC regions. On the basis of afferents distribution three territories can be distinguished in this cortex. The first or ventral territory involving ventral and ventrolateral PFC (subgenual, subproreal and orbital, paraorbital areas) is reached only by VM afferents. In the second, dorsal PFC territory (proreal and medial precruciate areas) afferents originated in VM and VA thalamic nuclei terminate. The third cortical territory, involving the extreme caudal belt of the frontal association cortex (dorsal and posterior precruciatal region as well as the anterior composite area of the lateral presylvian wall), is reached by VM, VA and VL projections. The density of these projections increases in the caudal direction. VM and VA afferents are concentrated in the medial precruciate PFC-PMC area, whereas VL afferent in the dorsal PMC and fissural region.