UBC Theses and Dissertations
Implicit and explicit adaptation processes during visuomotor adaptation of manual aiming movements Larssen, Beverley Christine
In this thesis I investigate how people adapt manual aiming in novel visual-motor environments and how different adaptation processes (implicit/explicit) depend on feedback type, and existing internal models (action experience). How implicit and explicit processes interact to facilitate accurate performance in adaptation paradigms is debated. One key study concluded that implicit adaptation, driven by error in expected sensory consequences, guided adaptation independent of ‘correct’ strategic/explicit processes (Mazzoni & Krakauer, 2006). We hypothesized that if these processes are independent, later explicit re-adaptation should not influence a previously acquired implicit adaptation (evidenced by unchanged after-effects). In Experiment 1, numeric post-trial knowledge of results (KR) was used to promote explicitly-guided, re-adaptation of an implicit adaptation. Thirty participants gradually adapted aiming movements to a 30° CW visual rotation to achieve implicit adaptation (evidenced by strong after-effects). Participants practiced again with correct or incorrect (+/-15°) KR about cursor endpoint accuracy while still receiving correct cursor feedback. The incorrect KR groups showed the highest variable error, indicative of error-reducing strategic adjustments. Only the +15° error group re-adapted to KR. This resulted in larger after-effects than before KR exposure. If KR engaged only explicit processes, these results would suggest that these processes are interdependent, whereby an (implicit) internal model for aiming was updated by explicit processes, resulting in augmented after-effects. Despite existing evidence suggesting that post-trial KR facilitates only explicit adaptation, we had to test this result in our research design before concluding that the effects of KR were unique to re-adaptation. Therefore, we conducted Experiment 2 to determine whether post-trial KR could be used to update internal models for aiming without previous visual-motor experience. Thirty participants gradually adapted to a 30° CW visual rotation receiving either concurrent or post-trial cursor feedback, or post-trial numeric KR. Although all groups showed after-effects following practice, suggesting implicit adaptation in all feedback conditions, the magnitude of after-effects was smaller for the numeric KR group. From these data we conclude that numeric KR results in both implicit and explicit adaptation and that the relative contributions of these processes to adaptation likely depends on self-attribution of errors and timing of visual feedback.
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