UBC Theses and Dissertations
Visuomotor adaptation : contributions of awareness, online correction, and sense of agency Cameron, Brendan D.
Our sensorimotor system constantly monitors its performance, checking that movements unfold as intended, and modifying motor commands when error creeps in. When a systematic change in the environment is imposed, such as a shift in the visual feedback of the limb, the sensorimotor system adapts to this change, such that when the perturbation is removed the system initially responds as though the perturbation were still present (so-called ‘aftereffects’). The current project investigates some of the factors that influence how the motor system responds when a systematic perturbation is introduced: How do awareness, explicit control, online control, and our sense of agency affect motor adaptation? To address these questions I apply two types of perturbation: perturbation of the target (Studies 1-3) and perturbation of visual feedback of the effector (Study 4). In Study 1, I investigate how a person’s awareness that a target has been perturbed influences how they learn from the reach error that this perturbation introduces. The study shows that awareness of a target perturbation dramatically undermines adaptation. In Study 2, I investigate how explicit control of a reaching movement influences adaptation to an unperceived target perturbation. The study shows that adaptation occurs even when participants are engaged in the explicit task of undershooting the target, suggesting that implicit motor processing can proceed while the system is busy with an explicit motor task. In Study 3, I investigate the influence of online error processing on reach adaptation, and I show that people adapt to a target perturbation regardless of whether error occurs during (online) or at the end of their reach. In Study 4, I investigate how a person’s agency over their movement influences how they learn from perturbed feedback. The study shows that a small amount of adaptation occurs when people have their limbs passively moved – a result of a shift in perceived limb location. The four studies, together, suggest that both error processing and sensory recalibration can contribute to aftereffects, but they also suggest that sensory feedback prediction during active reaching is the most important component of adaptation.
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