AFFERENT CONNECTIONS OF THE MEDIAL FRONTAL-CORTEX OF THE RAT .2. CORTICAL AND SUBCORTICAL AFFERENTS

In order to compare the frontal cortex of rat and macaque monkey, cort ical and subcortical afferents to subdivisions of the medial frontal c ortex (MFC) in the rat were analyzed with fluorescent retrograde trace rs. In addition to afferent inputs common to the whole MFC, each subdi vision of the MFC has a specific pattern of afferent connections. The dorsally situated precentral medial area (PrCm) was the only area to r eceive inputs from the somatosensory cortex. The specific pattern of a fferents common to the ventrally situated prelimbic (PL) and infralimb ic (IL) areas included projections from the agranular insular cortex, the entorhinal and piriform cortices, the CA1-CA2 fields of the hippoc ampus, the subiculum, the endopiriform nucleus, the amygdalopiriform t ransition, the amygdalohippocampal area, the lateral tegmentum, and th e parabrachial nucleus. In all these structures, the number of retrogr adely labeled cells was larger when the injection site was located in area IL. The dorsal part of the anterior cingulate area (ACd) seemed t o be connectionally intermediate between the adjacent areas PrCm and P L; it receives neither the somatosensory inputs characteristic of area PrCm nor the afferents characteristic of areas PL and IL, with the ex ception of the afferents from the caudal part of the retrosplenial cor tex. A comparison of the pattern of afferent and efferent connections of the rat MFC with the pattern of macaque prefrontal cortex suggests that PrCm and ACd areas share some properties with the macaque premoto r cortex, whereas PL and IL areas may have characteristics in common w ith the cingulate or with medial areas 24, 25, and 32 and with orbital areas 12, 13, and 14 of macaques. (C) 1995 Wiley-Liss, Inc.