Orbitofrontal cortex
From Psy3242
Overview
The orbitofrontal cortex (OFC) is located within the frontal lobe right above the eyes and is involved with such processes as decision making. As its functions involve emotion and reward, OFC is recognized by some to be part of the limbic system. The OFC is often a difficult area of photograph with functional magnetic resonance imaging (fMRI) because of its placement near air-filled sinuses which can lead to distorted images. Through neuroimaging, however, neurologists have found that expected reward value and other reinforcers activate the OFC.
Tests and Damage to Orbitofrontal Cortex
In the visual discrimination test, participants are shown two pictures, entitled A and B. Through the test they learn that when they push the button when picture A appears, they are rewarded, and when they press the button when picture B is displayed, they are punished. Once the participants have figured out this rule, it switches to the opposite so that now the participant is punished when they press the button for picture A. Normal subjects are usually able to adjust quickly to the change, but those with OFC damage continue to respond with the original pattern of reinforcement despite being punished for it. Furthermore, patients usually come to understand that the rule has changed yet are unable to adjust to the change. Over time, the test changes so that pressing the button for either A or B is punishable. The correct response is to refrain from pushing the button at all, but patients with damage to their OFC find this change equally challenging.
The Iowa gambling task creates a situation that resembles, as much as possible, instances of real-life decision making by involving uncertain outcomes and reward and punishment. The task specifically measures emotion-based learning. Subjects are shown four virtual decks of cards on a computer screen. They must choose one card at a time. For some cards they will win money and for others they will lose money. For example, cards chosen from pack A and B result in large immediate gain but also large long term loss. Cards chosen from C and D, however, result in smaller gains over time but less long term loss. The goal is for participants to realize that choosing cards from C and D is the best decision. The task, though, does not rely on long debates over what card should be chosen, but instead relies on the gut reaction of the participant. Most participants over time learn to pick from the good decks and to stay away from the bad. In addition, they experience a measurable stress reaction while hovering over the bad decks. Patients with OFC damage, though, do not experience the same reaction and therefore more willingly pick the bad decks.
Subjects with OFC damage, as demonstrated by several other tests, are unable to judge when something is socially awkward although they are able to recount the events leading up to the situation perfectly.
Damage to the OFC usually leads to a pattern of disinhibited behavior such as swearing and poor social interaction. Patients with damage are usually unable to manage their finances properly and tend to make rash decisions.
