Explicit (strategic) and implicit (unconscious) processes play a role in visuomotor adaptation (Bond and Taylor, J Neurophysiol 113:3836-3849, https://doi.org/10.1152/jn.00009.2015 , 2015; Werner et al., PLoS ONE 10:1-18, https://doi.org/10.1371/journal.pone.0123321 , 2015). We investigated the contributions of explicit and implicit processes to visuomotor adaptation when awareness was manipulated directly vs. indirectly, and asked how these contributions changed over time. Participants were assigned to a Strategy or No-Strategy group. Those in the Strategy group were made aware of the visuomotor distortion directly. Participants were further subdivided into groups to train with a large (60°), medium (40°) or small (20°) visuomotor distortion, providing the potential for awareness to develop indirectly. Participants reached with their respective distorted cursor, followed by a series of no-cursor reaches to assess the contributions of explicit and implicit processes to visuomotor adaptation after every 30 reach training trials. Within the no-cursor reaching trials, participants reached (1) with any strategies they had gained during training (explicit + implicit processes), and (2) as accurately to the target as possible (implicit processes). Results showed that implicit contributions were greatest in the No-Strategy group, took time to develop, and were transient, as partial decay was seen following a 5-min rest. As well, implicit contributions were similar (i.e., plateaued), regardless of the rotation size participants trained with. In contrast, explicit contributions were greatest in the Strategy group, increased with rotation size, and remained consistent over time. Taken together, results reveal that there are notable differences in the stability of explicit and implicit processes and their potential to contribute to visuomotor adaptation depending on if awareness is provided directly.
Keywords: Awareness; Explicit adaptation; Implicit adaptation; Motor learning; Time course.