THE ROLE OF GENERALISATION AND CONTEXTUAL CUES IN MOTOR ADAPTATION TO NOVEL VISUAL ENVIRONMENTS

Woolley, Daniel Graham (2007). THE ROLE OF GENERALISATION AND CONTEXTUAL CUES IN MOTOR ADAPTATION TO NOVEL VISUAL ENVIRONMENTS PhD Thesis, School of Human Movement Studies , University of Queensland.

       
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Author Woolley, Daniel Graham
Thesis Title THE ROLE OF GENERALISATION AND CONTEXTUAL CUES IN MOTOR ADAPTATION TO NOVEL VISUAL ENVIRONMENTS
School, Centre or Institute School of Human Movement Studies
Institution University of Queensland
Publication date 2007
Thesis type PhD Thesis
Supervisor Dr Stephan Riek
Abstract/Summary The series of experiments which form this thesis investigate the generalisation of visuomotor learning. The thesis consists of seven chapters, with the first chapter providing a general introduction to the research program, and the final chapter a summary of the main research findings. Chapters 2 to 6 each represent stand-alone scientific works. Chapter 2 is a review of previous work examining the constraints imposed by the central nervous system on the generalisation of visuomotor learning in behavioural tasks. Particular consideration is given to tasks which have investigated how adaptation to a visuomotor rotation transfers to new visual target locations and movement directions. The role of contextual information in facilitating dual adaptation to opposing novel environments which are initially prone to interference is also discussed. The study described in Chapter 3 first assessed if movements made with a custom designed two degree of freedom isometric torque manipulandum would manifest a typical pattern of motor adaptation when subjects were exposed to a single visuomotor rotation. Two groups of subjects were trained to a single visuomotor rotation, which were of a different magnitude and in opposite directions for each group. Following a rapid improvement in performance to the rotated environment over the course of the training block, directional after-effects were observed on return to the non-rotated environment. Once it was confirmed that our task produced a typical pattern of adaptation to a single visuomotor rotation, we then examined if colour cues provided a suitable source of contextual information to facilitate dual adaptation to two directionally opposed visuomotor rotations of unequal magnitude, which were concurrently presented to the same set of visual targets. A performance improvement over the course of training occurred to only one of the visuomotor rotations, with the possibility of a performance decrement to the other. The absence of after-effects following training indicated that adaptation did not occur in a similar manner to that observed in the single visuomotor rotation groups. The study presented in chapter 4 further investigated constraints on the ability of subjects to dual adapt to opposing visuomotor rotations. We tested if colour cues, a separation in workspace, and presentation schedule, could be used to distinguish between two opposing visuomotor rotations and enable dual adaptation. The opposing visuomotor rotations were either presented in the same region of workspace and each associated with colour cues, presented in different regions of workspace in addition to colour cues, or presented in different regions of workspace only. We also assessed the effectiveness of the workspace separation with both randomised and alternating presentation schedules. The results indicated that colour cues were not effective at enabling dual adaptation when each of the visuomotor rotations was associated with the same region of workspace. When associated with different regions of workspace, however, dual adaptation to the opposing rotations was successful regardless of whether colour cues were present or the type of presentation schedule. The purpose of the study described in chapter 5 was to determine if target amplitude would serve as an appropriate source of contextual information to enable dual adaptation. This was tested by associating two opposing visuomotor rotations with a set of visual targets that were matched in angular direction but of different amplitude. The two sets of visual target amplitudes also resulted in movements of different amplitude. The results indicated that visual target and movement amplitude is not a suitable source of contextual information to enable dual adaptation. Interference was observed in groups who were exposed to opposing visuomotor rotations, or a visuomotor rotation and no rotation, both when the onset of the visuomotor rotations was sudden, or occurred gradually over the course of training. Furthermore, the pattern of interference indicated that the inability to dual adapt was the result of the generalisation of learning between the two visual target and movement amplitudes. Chapter 6 describes a series of experiments in which we used a dual adaptation paradigm to assess if distinct patterns of generalisation for visuomotor learning were manifested in the visual and motor workspaces. By manipulating the position of the visual targets and the magnitude and direction of the visuomotor rotations, we were able to independently determine the extent of generalisation in the visual and motor workspaces during the adaptation phase of the task. When the set of targets associated with each of the opposing visuomotor rotations were near in the visual workspace and separate in the motor workspace, extensive interference was observed. In the reverse scenario when the targets were separate in the visual workspace and near in the motor workspace, only a limited degree of interference was present. The dominance of generalisation in the visual workspace was supported by the result that dual adaptation to opposing visuomotor rotations was found to occur when separate targets in the visual workspace required movements to overlapping targets in the motor workspace.

 
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Created: Fri, 21 Nov 2008, 16:35:58 EST