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          Institute: MPI für biologische Kybernetik     Collection: Biologische Kybernetik     Display Documents



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ID: 39385.0, MPI für biologische Kybernetik / Biologische Kybernetik
Phosphene Thresholds Evoked by Transcranial Magnetic Stimulation are Insensitive to Short-lasting Variations in Ambient Light
Authors:Kammer, T.; Beck, S.
Date of Publication (YYYY-MM-DD):2002
Title of Journal:Experimental Brain Research
Volume:145
Issue / Number:3
Start Page:407
End Page:410
Review Status:not specified
Audience:Not Specified
Intended Educational Use:No
Abstract / Description:Abstract
Transcranial magnetic stimulation applied over the occipital pole is able to induce the perception of light flashes called phosphenes. For phosphene detection and threshold measurement subjects are usually blindfolded or investigated in the dark. The question that we posed here is whether phosphene thresholds change with variations in ambient light. In six subjects we measured thresholds under four different conditions: closed eyes (5 minutes of adaptation) and 0.5, 100, and 3200 cd/m2 background illumination. No systematic change in phosphene thresholds was observed with different lighting conditions. In three subjects we repeated the measurements after one week and again found similar values with no systematic modulation. Our data show that cortical excitability does not change with different light adaptation levels. This confirms that the main adaptation to light takes place at subcortical levels, namely at the retina. The practical conclusion is that it is unnecessary to blindfold subjects when determining phosphene thresholds.
External Publication Status:published
Document Type:Article
Communicated by:Holger Fischer
Affiliations:MPI für biologische Kybernetik/Emeriti
Identifiers:LOCALID:1571
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