Behavioral characteristics and neural localization of sensorimotor adaptation

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    The present thesis investigates behavioral characteristics of sensorimotor adaptation and its neural localization. This special form of motor learning occurs whenever an altered environment requires the adjustment of already existing motor behavior. Sen-sorimotor adaptation does not only play a dominant role in everyday life, but it is also an intrinsic element in the field of sports. For instance, tennis players have to adjust their movements to rackets, balls or field conditions. In the following, the main results of the individual studies of this thesis as well as their implications are summa-rized.
    To this day, it is not entirely clear whether explicit knowledge has a beneficial or a detrimental effect on sensorimotor adaptation. This thesis therefore tries to determine the role of explicit knowledge in sensorimotor adaptation, and is the first to reveal a positive effect of explicit knowledge on adaptation. In particular, our results lead to the assumption that the positive effect is related to strategic control. Furthermore, they suggest that an involvement of the dorsolateral prefrontal cortex leads to improved sensorimotor adaptation.
    Furthermore, the present thesis scrutinizes whether adaptation to different alterations of feedback is based on common principles. It compares the adaptive processes caused by a rotation and a reversal of visual feedback, and it shows for the first time that adaptation to reversed vision is based on the same continuous and discrete pro-cesses as adaptation to visual rotations. According to this finding, similar neuronal networks for both adaptive processes can be assumed.
    The thesis also investigates whether adaptation to a change of visual feedback is a directionally local or a global phenomenon. We show that variable practice in all directions does not lead to an improved adaptation to a visual rotation, which is thought to be achieved by directionally tuned modules. Accordingly, variable prac-tice does presumably not induce a greater generalization or a global adaptation pro-cess, respectively. Also, we show direction-specific adaptive processes during adap-tation to reversed vision. Moreover, transfer to unpracticed targets could well be predicted by the superposition of neighboring adapted modules. These results lead to
    the conclusion that adaptation to reversed visual feedback is based on a local process. This finding is associated with the involvement of Gaussian tuned neural units in sensorimotor adaptation.
    Finally, this thesis scrutinizes the contribution of the cerebellum to sensorimotor ad-aptation by investigating adaptation processes and motor performance in two cere-bellar patient groups. In particular, we investigate whether different parts of the cere-bellum play different roles during adaptation. The results suggest that adaptive recal-ibration is impaired in patients with cerebellar cortical degeneration as well as in patients with lesions within the territory of the superior cerebellar artery. The findings further indicate an intact recalibration but degraded strategic control in patients with lesions within the territory of the posterior inferior cerebellar artery. A partitioning-of-variances analysis supports the suggestion that (superior) cerebellar regions are exclusively involved in motor performance or are involved in both motor performance and adaptation.
    Original languageEnglish
    Place of PublicationKöln
    Publication statusPublished - 2010