Spontaneous fluctuations in posterior alpha-band EEG activity reflect variability in excitability of human visual areas

Romei, V., Brodbeck, V., Michel, C., Amedi, A., Pascual-Leone, A. and Thut, G. (2008) Spontaneous fluctuations in posterior alpha-band EEG activity reflect variability in excitability of human visual areas. Cerebral Cortex, 18(9), pp. 2010-2018. (doi: 10.1093/cercor/bhm229)

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Abstract

Neural activity fluctuates dynamically with time, and these changes have been reported to be of behavioral significance, despite occurring spontaneously. Through electroencephalography (EEG), fluctuations in alpha-band (8-14 Hz) activity have been identified over posterior sites that co-vary on a trial-by-trial basis with whether an upcoming visual stimulus will be detected or not. These fluctuations are thought to index the momentary state of visual cortex excitability. Here, we tested this hypothesis by directly exciting human visual cortex via transcranial magnetic stimulation (TMS) to induce illusory visual percepts (phosphenes) in blindfolded participants, while simultaneously recording EEG. We found that identical TMS-stimuli evoked a percept (P-yes) or not (P-no) depending on pre-stimulus alpha-activity. Low pre-stimulus alpha-band power resulted in TMS reliably inducing phosphenes (P-yes trials), whereas high pre-stimulus alpha-values led the same TMS-stimuli failing to evoke a visual percept (P-no trials). Additional analyses indicated that the perceptually relevant fluctuations in alpha-activity/visual cortex excitability were spatially specific and occurred on a sub-second time-scale in a recurrent pattern. Our data directly link momentary levels of posterior alpha-band activity to distinct states of visual cortex excitability, and suggest that their spontaneous fluctuation constitutes a visual operation mode that is activated automatically even without retinal input.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Thut, Professor Gregor
Authors: Romei, V., Brodbeck, V., Michel, C., Amedi, A., Pascual-Leone, A., and Thut, G.
College/School:College of Science and Engineering > School of Psychology
College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Cerebral Cortex
ISSN:1047-3211
ISSN (Online):1460-2199
Published Online:18 December 2007

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