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Title

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

Authors
Amedi, Amir
Pascual-Leone, Alvaro
Published in Cerebral Cortex. 2008, vol. 18, no. 9, p. 2010-8
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 covary 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 prestimulus alpha-activity. Low prestimulus alpha-band power resulted in TMS reliably inducing phosphenes (P-yes trials), whereas high prestimulus 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 subsecond 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.
Keywords AdultAlpha RhythmAttention/physiologyEye Movements/physiologyFemaleHumansMalePhosphenes/physiologySleep Stages/physiologyTranscranial Magnetic StimulationVisual Cortex/physiologyVisual Perception/physiology
Identifiers
PMID: 18093905
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Research group Organisation et plasticité des réseaux neuronaux cérébraux (148)
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(ISO format)
ROMEI, Vincenzo et al. Spontaneous fluctuations in posterior alpha-band EEG activity reflect variability in excitability of human visual areas. In: Cerebral Cortex, 2008, vol. 18, n° 9, p. 2010-8. https://archive-ouverte.unige.ch/unige:734

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Deposited on : 2009-02-09

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