A key role for stimulus-specific updating of the sensory cortices in the learning of stimulus–reward associations

Successful adaptive behavior requires the learning of associations between stimulus-specific choices and rewarding outcomes. Most research on the mechanisms underlying such processes has focused on subcortical reward-processing regions, in conjunction with frontal circuits. Given the extensive stimulus-specific coding in the sensory cortices, we hypothesized they would play a key role in the learning of stimulus-specific reward associations. We recorded electrical brain activity (using electroencephalogram) during a learning-based decision-making gambling task where, on each trial, participants chose between a face and a house and then received feedback (gain or loss). Within each 20-trial set, either faces or houses were more likely to predict a gain. Results showed that early feedback processing (~200-1200 ms) was independent of the choice made. In contrast, later feedback processing (~1400-1800 ms) was stimulus-specific, reflected by decreased alpha power (reflecting increased cortical activity) over face-selective regions, for winning-vs-losing after a face choice but not after a house choice. Finally, as the reward association was learned in a set, there was an increasingly stronger attentional bias towards the more likely winning stimulus, reflected by increasing attentional orienting-related brain activity and increasing likelihood of choosing that stimulus. These results delineate the processes underlying the updating of stimulus-reward associations during feedback-guided learning, which then guide future attentional allocation and decision-making.