Distinct Neural Signatures of Reward and Sensory Prediction Error in Motor Learning

Two distinct processes contribute to changes in motor commands during reach adaptation: reward based learning and sensory error based learning. In sensory error based learning, the mapping between sensory targets and motor commands is recalibrated according to error feedback. In reward based learning, motor commands are associated with subjective value, such that successful actions are reinforced. We recorded EEG from humans of either sex to identify and dissociate the neural correlates of reward prediction error (RPE) and sensory prediction error (SPE) during learning tasks designed to isolate each response. We designed a visuomotor rotation task to isolate sensory error based learning in response to SPE, which was induced by altered visuospatial feedback of hand position. In a reward learning task, we isolated learning in response to RPE, which was induced by binary reward feedback. We found that a fronto-central event related potential called the feedback related negativity occurred specifically in response to RPE during reward based learning, while a more posterior component called the P300 was associated with SPE during a visuomotor rotation task. These findings reveal a dissociation between well characterized EEG signatures of error processing in two distinct motor learning processes.