Effects of Apparent Body Size on Motor Function

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 DESCRIPTION (provided by applicant): Changing the apparent size of the body using magnifying lenses has been demonstrated to influence perceptual judgments about the body as well as judgments of pain intensity. In preliminary data from normal and brain lesion subjects we have demonstrated for the first time that altering the apparent size of the body influences motor processing as well. More specifically, magnifying the image of the hand improved both finger tapping and grip strength. The major objective of the proposed study is to systematically explore the effects of magnification on finger tapping rate, grip strength, reach-to-grasp and finger individuation tasks in subjects with brain lesions. A secondary objective is to identify the mechanisms underlying this effect; to that end, three experiments involving Transcranial Magnetic Stimulation will be performed in normal subjects. The proposed investigations have clear and substantial clinical implications. The demonstration that a simple, inexpensive and safe intervention enhances motor function would provide a novel and potentially efficacious therapeutic intervention that may serve to augment current rehabilitation practices. The proposed investigations are also of theoretical significance. Magnification effects on motor processing are a manifestation of the general phenomenon of cross-modal integration/modulation that is crucial for all sensory-motor processing. Our work will provide important information regarding the neural mechanisms underlying this basic and ubiquitous phenomenon.