The orbitofrontal cortex and response selection

Abstract

Orbitofrontal cortex (OFC) function is often characterized in terms of stimulus-reward mapping; however, more recent evidence suggests that the OFC may play a role in selecting and representing extended actions. First, previously encoded reward associations in the OFC could be used to inform responding in novel but similar situations. Second, when evaluated in tasks requiring the animal to perform extended actions, response selective activity can be recorded in the OFC. Finally, the interaction between the OFC and hippocampus illustrates OFC's role in response selection. The OFC may facilitate reward-guided memory retrieval by selecting the memories most relevant to achieve a goal. This model for OFC function places it within the hierarchy of increasingly complex action representations that support decision making.

Figure 1

Knowledge of previously rewarded paths may help generate novel responses. (A) Rats trained on repeated spatial reversals no longer require the OFC. Further, animals trained on repeated strategy switches—an OFC-independent task—no longer require the OFC on subsequent reversals. (B) Because strategy switching in this task has a common path with spatial reversal, knowledge of the rewarded paths learned during strategy switching may be used to support responding during later reversals. (C) A sample experiment for testing the prospective function of the OFC. Animals would be trained to go north rather than south on the plus-maze. Later the animals would be tested on going north via a different path. If the OFC contributes to selecting novel responses, then the OFC lesions should impair this new discrimination.

Figure 2

The OFC and hippocampus may interact through different mechanisms to support reward-guided memory retrieval. (A) OFC path coding could be composed of the combined activity of hippocampal place fields to which the expected reward could be associated. (B) Alternatively, OFC coding could activate hippocampal place fields along rewarded paths, generating prospective and retrospective coding in the hippocampus.