355 Learning Related Power Changes in Caudate Nucleus

Abstract

Abstract INTRODUCTION Associative learning is the process whereby a connection is formed between a sensory cue and an outcome resulting from a behavioral response. This process allows us to learn to adapt and optimally respond to a changing environment. Primate research has demonstrated that the caudate nucleus is involved in associative learning and contains information encoding whether a response was correct or incorrect. Our objective was to determine whether correlates of learning are present in the human caudate nucleus and to differentiate between learning and reward related signaling. METHODS Five subjects who underwent depth electrode placement for seizure localization for medically refractory epilepsy were included in our study. Two behavioral tasks were performed while intracranial local field potentials were recorded from the implanted electrodes. A learning task required subjects to learn an association between a series of presented images and a button press. A gambling task required subjects to place a wager on the outcome of a simulated card game. We computed power in caudate electrodes and compared power during the feedback epoch of the task between correct and incorrect trials for the learning task and between winning and losing trials for the gambling task. RESULTS >There was a significant increase in beta (15-30Hz) power during the feedback epoch of the learning task, with significant differences between beta power following correct versus incorrect responses. Conversely, no difference in beta power was seen during the feedback epoch of the gambling task between winning and losing trials. CONCLUSION Changes in beta power were seen in the caudate nucleus that differed between correct and incorrect trials in a learning task. No correlate was seen in a gambling task, suggesting that this signal is related specifically to learning rather than to reward.