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Do Virtual Lesions of Parietal Cortex Disrupt Online Control of Goal-Directed Movements?

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Reichenbach,  A
Department Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Former Department MRZ, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Reichenbach, A. (2007). Do Virtual Lesions of Parietal Cortex Disrupt Online Control of Goal-Directed Movements? Diploma Thesis, Eberhard-Karls-Universität, Tübingen, Germany.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-CE4B-B
Abstract
According to the nowadays preferred integrative hybrid model for planning and executing goal-directed movements, an initial motor plan is calculated prior to movement onset and subsequently feedback information is used to update this plan continuously during movement execution. In this continuous online control of the movement, the posterior parietal cortex (PPC) is involved critically. To enable a detailed and comprehensive research of the processes and brain areas involved in reaching, a virtual reality environment with the possibilities for manipulating visual and proprioceptive feedback information is set up, and equipment for transcranial magnetic stimulation (TMS) is integrated. The setup offers the possibility to study the chronometry of the processes and the localization of crucially involved brain areas. Five main conditions are implemented: Undetected displacement of the visual target, undetected displacement of visual hand feedback, rotation of visual hand feedback, application of a force to the hand and (as control) no alteration of visual or haptic scene. All conditions can be conducted with and without hand feedback and with and without TMS stimulation. As proof of concept, a pilot study is conducted that replicates the study of Desmurget, Epstein, Turner, Prablanc, Alexander, and Grafton (1999). In this study, they could show that the updating of a reaching movement towards an unconsciously displaced target can be disturbed by applying TMS over the contralateral PPC. Additionally to the replication of this disturbance, the possibility to localize the affected cortical area more precisely than in the original study is demonstrated in the pilot study.