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  Transcranial magnetic stimulation in the visual system: I. The psychophysics of visual suppression

Kammer, T., Puls, K., Strasburger, H., Hill, N., & Wichmann, F. (2005). Transcranial magnetic stimulation in the visual system: I. The psychophysics of visual suppression. Experimental Brain Research, 160(1), 118-128. doi:10.1007/s00221-004-1991-1.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-D683-E Version Permalink: http://hdl.handle.net/21.11116/0000-0004-DCF0-5
Genre: Journal Article

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Kammer, T1, 2, Author              
Puls, K1, 2, Author              
Strasburger, H, Author
Hill, NJ2, 3, Author              
Wichmann, FA2, 3, Author              
Affiliations:
1Former Department Comparative Neurobiology, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497800              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497794              
3Department Empirical Inference, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497795              

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 Abstract: When applied over the occipital pole, transcranial magnetic stimulation (TMS) disrupts visual perception and induces phosphenes. Both the underlying mechanisms and the brain structures involved are still unclear. The first part of the study characterizes the suppressive effect of TMS by psychophysical methods. Luminance increment thresholds for orientation discrimination were determined in four subjects using an adaptive staircase procedure. Coil position was controlled with a stereotactic positioning device. Threshold values were modulated by TMS, reaching a maximum effect at a stimulus onset asynchrony (SOA) of approx. 100 ms after visual target presentation. Stronger TMS pulses increased the maximum threshold while decreasing the SOA producing the maximum effect. Slopes of the psychometric function were flattened with TMS masking by a factor of 2, compared to control experiments in the absence of TMS. No change in steepness was observed in experiments using a light flash as the mask instead of TMS. Together with the finding that at higher TMS intensities, threshold elevation occurs even with shorter SOAs, this suggests lasting inhibitory processes as masking mechanisms, contradicting the assumption that the phosphene as excitatory equivalent causes masking. In the companion contribution to this one we present perimetric measurements and phosphene forms as a function of the stimulation site in the brain and discuss the putative generator structures.

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 Dates: 2005-01
 Publication Status: Published in print
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 Rev. Method: -
 Identifiers: DOI: 10.1007/s00221-004-1991-1
BibTex Citekey: 2015
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Title: Experimental Brain Research
  Other : Exp. Brain Res.
Source Genre: Journal
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Publ. Info: Heidelberg : Springer-Verlag
Pages: - Volume / Issue: 160 (1) Sequence Number: - Start / End Page: 118 - 128 Identifier: ISSN: 0014-4819
CoNE: https://pure.mpg.de/cone/journals/resource/954925398496