Prefrontal connections of the perirhinal and postrhinal cortices in the rat

Abstract

Knowing how prefrontal regions interact with medial temporal lobe structures is important for understanding memory and cognition. Using anterograde and retrograde tract tracing methods in the rat, we report a detailed study of the perirhinal (PER) and postrhinal (POR) connections with the lateral, ventrolateral, and medial orbitofrontal cortices (ORBl, ORBvl, ORBm), infralimbic and prelimbic cortices (IL, PL), ventral and dorsal anterior cingulate cortices (ACAv, ACAd), and secondary motor cortex (MOs). Our analyses included the topography and laminar patterns of these connections. The PER and POR showed reciprocal connectivity with all prefrontal regions examined, but the patterns of connections differed. In general, PER areas 36 and 35 showed patterns of connectivity that were more similar to each other than to those of the POR. Analysis of anterograde tracers showed that PER areas 36 and 35 provide the strongest projections to prefrontal regions. The heaviest fiber labeling was in IL and PL, closely followed by orbital regions. Fiber labeling arising from injections in POR was weaker overall. The strongest POR efferents targeted MOs, ACAv, and ORBvl. For return projections, analysis of retrograde tracers showed that PER areas 36 and 35 receive strong inputs from orbitofrontal and medial prefrontal regions. Interestingly, PER also received substantial inputs from MOs and ACAd. The POR receives a very strong input from MOs, followed by ACAd, and ORBvl. Based on comparison of our findings with those obtained in monkeys, we argue that the rodent ACAd and MOs may be a functional homolog of the primate dorsolateral prefrontal cortex.

Age-Related Alterations in Prelimbic Cortical Neuron Arc Expression Vary by Behavioral State and Cortical Layer

“…The prelimbic cortex sends dense projections to both PER subdivisions areas 35 and 36, which originate from both deep and superficial cortical layers (Burwell and Amaral, 1998;Hwang et al, 2018). Dense retrograde labeling across cortical layers was also observed in the current experiment, and this did not vary between the young and old age groups.…”

Age-related alterations in prelimbic cortical neuronArcexpression vary by behavioral state and cortical layer

“…The prelimbic cortex sends dense projections to both PER subdivisions areas 35 and 36, which originate from both deep and superficial cortical layers (Burwell and Amaral, 1998;Hwang et al, 2018). Dense retrograde labeling across cortical layers was also observed in the current experiment, and this did not vary between the young and old age groups.…”

Basal Forebrain Nuclei Display Distinct Projecting Pathways and Functional Circuits to Sensory Primary and Prefrontal Cortices in the Rat

“…The bidirectional connectivity between mPFC and BF has attracted great interest as a circuit involved in modulating decision making, cortical arousal, and learning and memory ( Groenewegen and Uylings, 2000 ; Miller and Cohen, 2001 ; Dalley et al, 2004 ; Henny and Jones, 2008 ; Wise, 2008 ; Ramanathan et al, 2009 ; Martinowich et al, 2012 ; Paolone et al, 2012 ; Bloem et al, 2014 ; Zaborszky et al, 2015 ). The connections between the mPFC and other cortical areas that apparently contribute to information processing seem to be specific topographically organized ( Hoover and Vertes, 2007 ; Bedwell et al, 2014 , 2015 ; Zaborszky et al, 2015 ). In such processes, the cholinergic, GABAergic and glutamatergic BF neuronal groups or subgroups probably play diverse and complementary roles.…”