Parsing decision making processes in prefrontal cortex: response inhibition, overcoming learned avoidance, and reversal learning.
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Reversal learning refers to the ability to inhibit or switch responding to an object when the object-reward contingency changes. Deficits in this process are related to social abnormalities, impulsiveness, and a number of psychiatric disorders. A range of neural regions play a role in this process, including dorsolateral prefrontal cortex (dlPFC), dorsomedial prefrontal cortex (dmPFC), and inferior frontal gyrus (IFG). However, determining the specific functional contribution of each region has proved difficult, in part because reversal learning involves multiple cognitive subprocesses such as error detection, inhibiting responding to formerly rewarded stimuli, and overcoming avoidance of previously punished stimuli. We used fMRI and an experimental task adapted from a recent neurochemical study in marmosets to parse neural responding to subprocesses of reversal learning during choice and feedback trial components. Error-feedback processing was associated with increased activity in dmPFC, dlPFC, and IFG whether participants were overcoming avoidance, inhibiting responding, or performing classic response reversal. Reduced activity in medial prefrontal cortex (mPFC) was associated with error-feedback processing for response inhibition but not overcoming avoidance. Conversely, there was significantly greater activity in anterior dmPFC during error-feedback processing in overcoming avoidance compared to response inhibition. A conjunction analysis confirmed that a striking overlap in activity was observed across the three conditions in IFG, dlPFC, and dmPFC. The results are consistent with conceptualizations of IFG function that emphasize modulating stimulus-response maps rather than purely response inhibition. The approach has implications for models of prefrontal function and neurocognitive perspectives on a range of behavioural abnormalities associated with impairments in decision making.