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  Phosphenes and transient scotomas induced by magnetic stimulation of the occipital lobe: their topographic relationship.

Kammer, T. (1999). Phosphenes and transient scotomas induced by magnetic stimulation of the occipital lobe: their topographic relationship. Neuropsychologia, 37, 191-198. Retrieved from http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6T0D-3VM6JW8-7_user=29041_coverDate=112F012F1998_rdoc=7_fmt=summary_orig=browse_srch=23toc234860231998239996299972351009!_cdi=4860_sort=d_docanchor=_acct=C000003178_version=1_url.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-E735-6 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-E736-4
Genre: Journal Article

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Kammer, T1, 2, Author              
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1Department Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497797              
2Former Department Comparative Neurobiology, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497800              

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 Abstract: Transcranial magnetic stimulation (TMS) of the visual cortex is known to induce phosphenes and is able to suppress visual perception. To address the topographic relationship of phosphenes and transient scotomas, the visual field of 10 normal subjects was investigated using a perimetric approach. The central visual field (diameter: 20 degrees) was tested at 32 sites. Perceptual thresholds were determined by presenting I ms test spots flashed with varying intensity in random order. TMS was applied with a focal figure-of-eight coil placed over the inion. All subjects perceived phosphenes, mostly restricted to one of the lower quadrants within the visual held. In 13 out of 15 investigations, a magnetic stimulus triggered 100 ms after the visual target resulted in a relative scotoma with threshold changes of 8 dB or more. In 9 of 13 investigations, scotomas coincided spatially with sketches of phosphenes made by subjects in a separate test. Scotomas covered only a small percentage of the total visual field, which may explain the failure of previous studies to find perceptual suppression with the focal coil. The present result demonstrates that phosphenes evoked during TMS can serve as a guide for optimal visual stimulus alignment in neuropsychological experiments. (C) 1999 Elsevier Science Ltd. All rights reserved.

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 Dates: 1999
 Publication Status: Published in print
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Title: Neuropsychologia
Source Genre: Journal
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Pages: - Volume / Issue: 37 Sequence Number: - Start / End Page: 191 - 198 Identifier: -