Year: 2013
Type: dissertation
Abstract: In common cases of goal directed motor behavior like grasping, pointing and throwing, humans navigate their own body in the external space to achieve desired physical effects. Hereby, the so-called internal models provide the basis of human motor control. They are based on mental representations of the movement kinematics and dynamics in a given environment, and fulfill two major functions: to translate targeted Euclidean positional codes into motor program, on the one hand, to estimate the current body state, and to predict the sensory consequence of the action by simulating the action flow, on the other. Hence, sufficient specification of the kinematic and dynamic movement parameters is essential. Context-related peculiarities need to be registered and countervailed to confer optimal motor control. The present work focuses on adaptation to sensorimotor transformations imposed by visuomotor rotations. The upcoming section gives a brief overview of the studies included in the present work. Study 1 investigates dual adaptation, i.e. concurrent adaptation to opposing visuomotor rotations. Particularly interesting was the effectiveness of different contextual cues, i.e. sensory information in the movement context differing between rotation conditions, which haven found to be crucial for dual adaptation. Consequently, visual and postural cues were compared with each other. Results were discussed in connection with previous studies indicating visual dominance in movement representation and control. In contrast to the aforementioned salient contextual cues, some sensory information in an action context could be more latent, for example, the spatial structure of a visual workspace, which has been addressed in Study 2. This study focused on a novel aspect of visuomotor adaptation, and more importantly, the subsequent generalization. It is based on the assumption that the spatial structure of the distal workspace is crucial for optimal motor learning. This approach was examined in three experiments by analyzing intra- and intermanual generalization of adaptation induced by visuomotor rotation. Rotation conditions that were concordant with the global structure of the visual workspace were found more advantageous compared to conditions discordant to the visual workspace. Results were discussed in the background of the general issue concerning the relevance of contextual similarity in motor learning. Hence, according to our approach, visuomotor rotations as well as other sensorimotor transformations are not isolated occurrences and must be understood as integrative part of the entire movement context. This approach was investigated more extensively in the study reported in Study 3. The study inspected the adaptation processes to opposing visuomotor rotations in a symmetrical workspace. Modular adaptation, use-dependent plasticity and spatial realignment theoretically were possible mechanisms to deal with the rotation scenario. Since these mechanisms lead to different predictions regarding generalization behavior, comparisons between predictions and empirical data were conducted. In spite of evidential advantages of modular structures in adaptive motor control, the current work could show a particular case of visuomotor transformation, in which modularity lacks efficiency. Empirical data indicate that the adaptive motor control employed the spatial realignment to accomplish adaptation more efficiently. Possible neurological processes underlying spatial realignment in this particular case was discussed. Generally, this work aimed to extent the previous research scope concerning sensorimotor adaptation by postulating new theoretical approaches, demonstrating related behavioral phenomena and disclosing novel topics for future works.
Source: RWTH Publications (RWTH Aachen)
Authors: Lei Wang, Jochen Müsseler
Language: English
Topic: Motor Control and Adaptation
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2728186480