Behavioural variability and cortical electrophysiological signals depend on recent outcomes during human reinforcement motor learning

The history of our actions and the outcomes of these represent important information, which can inform choices, and efficiently guide future behaviour. While unsuccessful (S-) outcomes are expected to lead to more explorative motor states and increased behavioural variability, successful (S+) outcomes lead to reinforcement of the previous action and thus exploitation. Here, we show that during reinforcement motor learning, humans attribute different values to previous actions when they experience S- vs. S+ outcomes. Behavioural variability after S- outcomes is influenced more by the previous outcomes compared to what is observed after S+ outcomes. Using electroencephalography, we show that neural oscillations of the prefrontal cortex encode the level of reinforcement (high beta frequencies) and reflect the detection of reward prediction errors (theta frequencies). The results suggest that S+ experiences overwrite previous motor states to a greater extent than S- experiences and that modulations in neural oscillations in the prefrontal cortex play a potential role in encoding the (changes in) movement variability state during reinforcement motor learning.