Projections of the orbitofrontal cortex to the parietal cortex in the rat

Abstract

The orbitofrontal cortex (OFC) has been shown to play a role in decision making and goal oriented behaviors. The parietal cortex has also been shown to contribute to goal oriented behaviors and movements. Though cell recording studies in primates have suggested a direct connection between the two regions, little is known about the anatomical interconnectivity, and even less is known in the rat cortex. In this study, I describe the cytoarchitectonic organization of the subregions of the OFC and parietal cortex and then utilized anterograde and retrograde tracing techniques to examine the projections of the OFC to the parietal cortex in the rat brain. The results show that the medial (MO), ventral (VO) and the medial half of the ventrolateral (VLO) orbitofrontal cortices had projections to the parietal cortex, while the lateral half of VLO, the lateral (LO) and dorsolateral (DLO) orbitofrontal cortices did not. These projections di ered in strength along the mediolateral axis, where the border of VO and VLO showed the strongest projection. Terminations of the projections were found to be strongest in the medial parietal association cortex (MPtA) with weaker projections to the lateral parietal association cortex (LPtA) and few if any in the posterior parietal cortex (PtP). There was also a difference in projections along the rostrocaudal axis, where the most caudal region of VLO showed a different projection pattern. This area projects strongest to LPtA and weaker to PtP with little or no projection to MPtA. Since MO, VO and medial VLO project similarly they may function together as part of the same cortical network, while LO, DLO and lateral VLO may be part of other networks. The results further suggest that caudal areas of the OFC may be connectionally and functionally different from the rostral areas of OFC in the rat brain.