Questions: Orbitofrontal Cortex and Reward Valuation

Question 1

A rat learns that lever A produces food and lever B does not. After reliably learning this, the contingencies are reversed: lever B now produces food and lever A does not. A rat with OFC lesions continues pressing lever A despite receiving no food. What does this reveal about the OFC's function?

• A. The OFC controls motor movements, so the lesioned rat cannot physically switch levers
• B. The OFC encodes and updates learned value representations, so damage causes the rat to act on stale, outdated reward values
• C. The OFC detects reward absence, so the lesioned rat cannot perceive that lever A no longer delivers food
• D. The OFC controls working memory, so the lesioned rat forgets the original training contingency

Answer: (B)

OFC-lesioned animals show perseveration — they keep choosing a previously rewarded option even after it stops paying off. The deficit is not in detecting reward absence (they can perceive the omission) nor in memory — it is in updating the value representation. The OFC tracks expected value in a way that is continuously revised by experience; without it, value tags remain frozen at their previous state and behavior is driven by those stale representations. The lesioned rat 'knows' lever A stopped working, but still acts as if the old value holds.

Question 2

Which best describes the computational role that distinguishes the OFC from the striatum in the reward system?

• A. The OFC generates the dopamine prediction error signal; the striatum receives and stores it
• B. The OFC encodes subjective expected value and updates those representations as contingencies change; the striatum handles action selection based on those values
• C. The OFC controls conscious awareness of reward; the striatum drives automatic approach behavior
• D. The OFC and striatum perform the same function, but the OFC operates on longer time scales

Answer: (B)

The OFC's defining role is flexible, experience-dependent value assignment — computing what an option is worth right now given current knowledge. The striatum is more tightly coupled to action selection: it translates value signals into approach and avoidance. The dopamine prediction error signal is the update input flowing into both, but it is the OFC that maintains and revises the value representations themselves. When contingencies change, the striatum needs the OFC to tell it the new value before it can select appropriately.

Question 3

OFC damage primarily impairs the ability to perceive rewards — lesioned animals can seldom accurately detect when a stimulus is rewarding or not, which is why they fail reversal learning tasks.

• T. True
• F. False

Answer: False

This is a critical misconception. OFC-lesioned subjects can perceive rewards normally — they respond to reward delivery and can detect when an outcome has changed. Their deficit is in updating value representations: they persist in choosing previously rewarded options even after the contingency has reversed. The problem is not perception of reward; it is revision of learned value. This is a much more specific computational failure, and it is only revealed in tasks requiring behavioral flexibility in response to changed contingencies.

Question 4

The Iowa Gambling Task reveals OFC-like impairment in people with addiction and psychopathy, suggesting these conditions share a mechanism involving disrupted learned value updating.

• T. True
• F. False

Answer: True

The Iowa Gambling Task requires integrating feedback over many trials to learn which decks are net positive in the long run. Patients with ventromedial PFC damage (the human OFC analog), as well as individuals with addiction and psychopathy, all tend to continue choosing net-negative decks. This convergence supports the idea that OFC dysfunction — specifically the failure to update learned values and redirect behavior away from currently unrewarding choices — is a shared mechanism across these populations, despite their otherwise distinct clinical profiles.

Question 5

Why does OFC damage produce perseveration in reversal learning tasks rather than simply reducing how much an animal values rewards in general?

Model answer: Perseveration reflects a specific failure to update value representations when contingencies change, not a failure to value rewards at all. OFC-lesioned animals still approach and consume rewards — their motivation and hedonic response are largely intact. The deficit is that the value tag previously associated with a stimulus cannot be revised when new experience contradicts it: the animal acts as if the old contingency still holds. A general reduction in reward valuation would reduce approach behavior across all stimuli; perseveration specifically disrupts the ability to abandon a previously rewarded strategy when it stops working, leaving motivation intact while disconnecting it from current outcomes.

This distinction is essential for understanding what the OFC actually computes. It is not a pleasure center — those functions are distributed across the broader reward circuit. The OFC's specific contribution is flexible, experience-dependent value updating. Perseveration after OFC damage is the behavioral signature of that specific computation going offline.