22Two distinct processes contribute to changes in motor commands during reach adaptation: 23 reward based learning and sensory error based learning. In sensory error based learning, the 24 mapping between sensory targets and motor commands is recalibrated according to error 25 feedback. In reward based learning, motor commands are associated with subjective value, 26 such that successful actions are reinforced. We recorded EEG from humans of either sex to 27 identify and dissociate the neural correlates of reward prediction error (RPE) and sensory 28 prediction error (SPE) during learning tasks designed to isolate each response. We designed a 29 visuomotor rotation task to isolate sensory error based learning in response to SPE, which was 30 induced by altered visuospatial feedback of hand position. In a reward learning task, we 31 isolated learning in response to RPE, which was induced by binary reward feedback. We found 32 that a fronto-central event related potential called the feedback related negativity occurred 33 specifically in response to RPE during reward based learning, while a more posterior component 34 called the P300 was associated with SPE during a visuomotor rotation task. These findings 35 reveal a dissociation between well characterized EEG signatures of error processing in two 36 distinct motor learning processes. CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under aThe copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/262576 doi: bioRxiv preprint first posted online Feb. 9, 2018; Page 3 Significance Statement 44Adaptation of motor output to changing task demands and dynamic environments is thought to 45 occur on the basis of distinct forms of prediction error. Reward prediction error occurs when 46 the subjective value of an outcome is different than the expected value, while sensory 47 prediction error occurs when the low-level sensory consequences of motor commands are 48 different than predicted. It remains unclear how EEG activity patterns associated with error 49 processing apply to these distinct forms of motor adaptation. We found that an event related 50 potential component called the feedback related negativity responded only to reward 51 prediction error, while the P300 component is modulated by sensory prediction error and 52 correlated to sensory error based learning.

Dopamine signaling is thought to mediate reward-based learning. We tested for a role of dopamine in motor adaptation by administering the dopamine precursor levodopa to healthy participants in two experiments involving reaching movements. Levodopa has been shown to impair reward-based learning in cognitive tasks. Thus, we hypothesized that levodopa would selectively impair aspects of motor adaptation that depend on reinforcement of rewarding actions.In the first experiment, participants performed two separate tasks in which adaptation was driven either by visual feedback of the hand position or binary reward feedback. We used EEG to measure event-related potentials evoked by task feedback. We hypothesized that levodopa would specifically diminish adaptation and the neural responses to feedback in the reward learning task. However, levodopa did not affect motor adaptation in either task nor did it diminish event-related potentials elicited by reward outcomes.In the second experiment, participants learned to compensate for mechanical force field perturbations applied to the hand during reaching. Previous exposure to a particular force field can result in savings during subsequent adaptation to the same force field and interference during adaptation to an opposite force field. We hypothesized that levodopa would diminish savings and anterograde interference, as previous work suggests that these phenomena result from a reinforcement learning process. However, we found no reliable effects of levodopa.These results suggest that reward-based motor adaptation, savings, and interference may not depend on the same dopaminergic mechanisms which have been shown to be disrupted by levodopa during various cognitive tasks.New and NoteworthyMotor adaptation relies on multiple processes including reinforcement of successful actions. Cognitive reinforcement learning is impaired by levodopa-induced disruption of dopamine function. We administered levodopa to healthy adults who participated in multiple motor adaptation tasks. We found no effects of levodopa on any component of motor adaptation. This suggests that motor adaptation may not depend on the same dopaminergic mechanisms as cognitive forms or reinforcement learning which have been shown to be impaired by levodopa.