Borders and cytoarchitecture of the perirhinal and postrhinal cortices in the rat

Abstract

Cytoarchitectonic and histochemical analyses were carried out for perirhinal areas 35 and 36 and the postrhinal cortex, providing the first detailed cytoarchitectonic study of these regions in the rat brain. The rostral perirhinal border with insular cortex is at the extreme caudal limit of the claustrum, consistent with classical definitions of insular cortex dating back to Rose ([1928] J. Psychol. Neurol. 37:467-624). The border between the perirhinal and postrhinal cortices is at the caudal limit of the angular bundle, as previously proposed by Burwell et al. ([1995] Hippocampus 5:390-408). The ventral borders with entorhinal cortex are consistent with the Insausti et al. ([1997] Hippocampus 7:146-183) description of that region and the Dolorfo and Amaral ([1998] J. Comp. Neurol. 398:25-48) connectional findings. Regarding the remaining borders, both the perirhinal and postrhinal cortices encroach upon temporal cortical regions as defined by others (e.g., Zilles [1990] The cerebral cortex of the rat, p 77-112; Paxinos and Watson [1998] The rat brain in stereotaxic coordinates). Based on cytoarchitectonic and histochemical criteria, perirhinal areas 35 and 36 and the postrhinal cortex were further subdivided. Area 36 was parceled into three subregions, areas 36d, 36v, and 36p. Area 35 was parceled into two cytoarchitectonically distinctive subregions, areas 35d and 35v. The postrhinal cortex was divided into two subregions, areas PORd and PORv. These regional definitions of perirhinal areas 35 and 36 and the postrhinal cortex were confirmed by new empirical analyses of previously reported quantitative connectional data (Burwell and Amaral [1998a] J. Comp. Neurol. 398:179-205).

The rat perirhinal cortex: A review of anatomy, physiology, plasticity, and function

“…Area 36 occupies the dorsal bank of the rhinal sulcus and area 35 occupies the ventral bank, extending slightly more rostrally than area 36 (Burwell, 2001). It is bordered rostrally by the posterior agranular insular cortex (bordering with areas 35 and 36) and the visceral area (area 36 only), caudally by the postrhinal cortex, dorsally by the ventral temporal association cortex and ventrally by the lateral entorhinal cortex ( Fig.…”

“…It is bordered rostrally by the posterior agranular insular cortex (bordering with areas 35 and 36) and the visceral area (area 36 only), caudally by the postrhinal cortex, dorsally by the ventral temporal association cortex and ventrally by the lateral entorhinal cortex ( Fig. 1a; Burwell et al, 1995;Burwell, 2001;Paxinos and Watson, 2005).…”

“…The borders between the perirhinal cortex and its neighbouring areas can be determined by cytoarchitectonic means, in particular the characteristic lack of a distinct layer IV in the perirhinal cortex (Burwell, 2001;Witter, 2002). Area 35 completely lacks layer IV while area 36 does have layer IV but it appears to be less well defined particularly in the medial portions of the cortex compared to other neocortical areas (Burwell et al, 1995).…”

“…Area 35 completely lacks layer IV while area 36 does have layer IV but it appears to be less well defined particularly in the medial portions of the cortex compared to other neocortical areas (Burwell et al, 1995). Brodmann's areas 35 and 36 are also cytoarchitectonically different in that layer I of area 35 tends to be thicker than that of area 36, the cells in area 35 are organised radially, the presence of large, heart-shaped pyramidal cells in layer V of area 35 and finally layers II and III are distinctly separated in area 36 and not in area 35 (Krieg, 1946b;Burwell and Amaral, 1998a,b;Burwell, 2001). Burwell (2001) further subdivides areas 35 and 36 into two subregions (ventral and dorsal) and three subregions (dorsal, ventral and posterior) respectively (Fig.…”

“…Although, there have been a number of reviews that have specifically examined the anatomy (e.g. Burwell, 2001;van Strien et al, 2010) and functional roles of the perirhinal cortex (Dere et al, 2007;Winters et al, 2008;Warburton and Brown, 2010), to date, there has been no review that brings anatomy, physiology, synaptic plasticity and function of the perirhinal cortex together. Here we attempt to bring these different strands together and also examine how the perirhinal cortex fits within the general hippocampal-parahippocampal circuitry with particular emphasis on the electrophysiological properties of these connections.…”