<p>Movement error-processing is central to both de novo learning and motor adaptation. Previous studies have distinguished behavioral mechanisms between these two motor learning types using visuomotor rotation perturbations to represent adaptation and mirror reversal for de novo learning. However, EEG markers identified during rotation training have not been directly compared with mirror reversal learning. In this exploratory study, participants (N = 32, 13 female) performed center-out reaching under a fixed rotation, mirror reversal, or random rotation while EEG was recorded during movement preparation and post-movement feedback. We compared EEG activity across early and late training and between small and large movement errors across perturbations. During preparation, the readiness potential showed opposite modulation in fixed and random rotations, suggesting greater reliance on updated internal models during adaptation. Mirror reversal showed no change, consistent with reliance on explicit strategies. Lateralized readiness potentials appeared to reflect planned movement direction rather than effector preparation. Moreover, beta attenuation for large errors and alpha synchronization for small errors were stronger in the fixed rotation than mirror reversal. During feedback, P3 amplitude decreased from early to late training in fixed and random rotations but remained stable in mirror reversal. A sustained late positivity followed small errors across perturbations, possibly indexing implicit learning. Random rotations also elicited distinct frontal and central beta modulation, consistent with disengagement under task unpredictability. While this should be considered a first exploratory study, we do identify distinct preparatory and feedback-related mechanisms across perturbation types.</p>