Time matters - The effect of time delays before and after goal directed reaching in visuomotor adaptation

Abstract

Through movement, we as humans can interact with our environment. Every movement takes place in a certain temporal context, because the right movement at the wrong time or the right movement coordinated differently in time can lead to a completely different, possibly wrong result. But not only the timing of the individual motor commands is important, also differences in the available time for the neuronal processes underlying the movement, such as movement planning or evaluation, can have an enormous influence. Time itself is often one of the most important variables in behavioral experiments, but also one of the most difficult ones to control. Thematically, this thesis focuses on the separation of adaptation into an explicit and an implicit component, and how through the manipulation of different time intervals in visuomotor rotation tasks, these can influence computational principles of visuomotor adaptation. First of, drawing on the example of the incomplete asymptote of adaptation, a phenomenon that shows that participants in such trials compensate for perturbation but usually leave a substantial residual error. It has been shown that this residual error is magnified when the time available for planning and preparing the movement is artificially reduced. This thesis shows that prolonging preparation time affects the asymptote in a similar way and can be the solution to overcoming residual errors. Furthermore, some studies have been able to show that a time delay of movement feedback leads to explicit processes becoming prevalent. Under this premise, this thesis investigated the phenomenon of temporal discounting of reward and showed that the explicit component can in fact overcome discounting. As most of the studies use some form of direct methods to measure for the explicit and implicit participation of adaptation, last but not least, this thesis attempted to use EEG, more specifically an event related potential, the feedback related negativity, as a proxy for mapping explicit and implicit processes at the neuronal level.