Functional Heterogeneity within Rat Orbitofrontal Cortex in Reward Learning and Decision Making

Abstract

Rat orbitofrontal cortex (OFC) is located in the dorsal bank of the rhinal sulcus, and is divided into the medial orbital area, ventral orbital area, ventrolateral orbital area, lateral orbital area, dorsolateral orbital area, and agranular insular areas. Over the past 20 years, there has been a marked increase in the number of publications focused on the functions of rat OFC. While collectively this extensive body of work has provided great insight into the functions of OFC, leading to theoretical and computational models of its functions, one issue that has emerged relates to what is defined as OFC because targeting of this region can be quite variable between studies of appetitive behavior, even within the same species. Also apparent is that there is an oversampling and undersampling of certain subregions of rat OFC for study, and this will be demonstrated here. The intent of the Viewpoint is to summarize studies in rat OFC, given the diversity of what groups refer to as "OFC," and to integrate these with the findings of recent anatomical studies. The primary aim is to help discern functions in reward learning and decision-making, clearing the course for future empirical work.

Keywords: OFC; basolateral amygdala; cognitive flexibility; devaluation; prefrontal cortex; reversal learning.

Figure 1.

Number of reports on OFC in all species. PubMed search terms “OFC,” “Orbitofrontal Cortex,” and “Orbital Prefrontal Cortex” from 1948 to 2014. The steepest rise in the number of publications occurred in the early 2000s, which was preceded by a more gradual increase in the 1990s. Rat studies, although increasing in number over the past decade, still account for a minority of reports on OFC.

Figure 2.

Parcellation of rat OFC as determined by anatomical tracing studies. Rat OFC is depicted in this ventral view of the right hemisphere. Adapted with permission from Rempel-Clower (2007). Rat OFC is divided in the MO, VO, VLO, LO, DLO, and AI areas. Numerals on upper right indicate the anterior (right)/posterior (left) distance (in millimeters) from bregma (Paxinos and Watson, 2007).

Figure 3.

Coronal sections depicting functional heterogeneity within rat OFC. Behavioral task effects are mapped onto coronal sections of rat OFC. Numerals on top of each section indicate the AP distance (in millimeters) from bregma (Paxinos and Watson, 2007).