Individual differences in frontal midline theta activity during visuomotor adaptation are related to execution noise

ABSTRACT Frontal midline EEG activity has been found to correlate with error magnitude during motor adaptation. We replicated a previous visuomotor adaptation experiment with very small perturbations, likely to invoke implicit adaptation, in a new group of 60 participants and combined it with EEG recordings. We used this data to explore 1) whether frontal midline activity will be evoked in the absence of awareness of the perturbation; 2) whether frontal midline activity is related to implicit adaptation; 3) whether individual differences in frontal midline activity are related to individual differences in motor learning. The results showed that frontal midline theta activity (FMΘ) is also present during small perturbations, does not drive between-trial error correction, and that the sensitivity of FMΘ to error magnitude was smaller for participants with greater execution noise. This relation between FMΘ-error-sensitivity and execution noise could be fully explained by looking at the relationship between FMΘ and error probability. This implies that frontal midline theta activity represents a surprise-like saliency signal, potentially driving awareness and cognitive control in situations with more salient errors.