Orbitofrontal cortex

Abstract

The orbitofrontal cortex is a large and heterogeneous cortical area on the ventral surface of the frontal lobe and is intimately involved in emotion and executive function. In this Primer, Peter Rudebeck and Erin Rich summarize our understanding of the mechanisms through which orbitofrontal cortex adaptively shapes decision making and affective behavior.

Figure 1.

Subregions of the human OFC. Ventral, lateral, and medial brain views are shown with OFC regions highlighted. While various parcellations of OFC into subregions have been proposed, most include divisions into areas 11, 13, 14, and 47/12.

Figure 2.

OFC anatomy and connectivity. (A) The major cortical and subcortical connections with OFC. PFC = prefrontal cortex, MD = mediodorsal, PAG = periaqueductal gray. (B) The first panel is a ventral view of the monkey brain with anterior temporal lobes removed to show OFC. A = Anterior, P = Posterior. The second panel is two thionin-stained sections of monkey OFC, oriented with the cortical surface at the top. There are higher cell densities in the middle layer (G) of the anterior section.

Figure 3.

Two classic tests of OFC function. (A) In reversal learning tasks, subjects first learn stimulus-reward associations. In this case, selecting circles will lead to reward and selecting triangles will lead to no reward. Next, these associations are reversed, so that the triangles predict reward and the circles predict no reward. The bottom panel shows typical performance of a normal subject. Once the first association is learned, they have a high accuracy for selecting the rewarding stimulus. At the onset of the reversal, performance drops below chance because the subject is not warned that contingencies have changed and they continue to select the circles, expecting this stimulus to be rewarded. With trial and error, they learn to stop selecting circles and instead select triangles to receive reward. (B) In devaluation tasks, subjects first learn a series of stimulus-reward associations. In this case, selecting circles will lead to peanuts, triangles will lead to raisins, stars and spirals will lead to no reward. After learning, the subject is given a preference test in which their options are stimuli that predict different types of rewards that are equally preferred. If they are not sated, they will choose circles or triangles with equal probability. If they are sated on peanuts, they will prefer to have raisins, and should select triangles. If they are sated on raisins, they will prefer peanuts and should select circles. OFC damage impairs devaluation, and abolishes satiety-specific preferences.

Figure 4.

Value-coding neurons in monkey OFC. On each trial, the subject saw a stimulus at time 0 that predicted a small, medium, or large reward. The lines show all the average neuronal activity on all trials of each type, aligned to the time the stimulus appeared. (A) Neuron 1 responded more to stimuli predicting large rewards (B) Neuron 2 responded more to stimuli predicting small rewards. Neurons with both types of responses are present in approximately equal proportions in monkey OFC.