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Cerebral Cortex Advance Access originally published online on April 18, 2008
Cerebral Cortex 2009 19(1):55-65; doi:10.1093/cercor/bhn056
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© The Author 2008. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Right Parietal Brain Activity Precedes Perceptual Alternation of Bistable Stimuli

Juliane Britz1,2, Theodor Landis3 and Christoph M. Michel1,2,3

1 Department of Fundamental Neuroscience, 2 Biomedical Imaging Center, University of Geneva, 3 Department of Neurology, University Hospital of Geneva, 1211 Geneva, Switzerland

Address correspondence to Juliane Britz, PhD, Department of Fundamental Neuroscience, Centre Medical Universitaire, 1, rue Michel Servet CH-1211 Geneva, Switzerland. Email: juliane.britz{at}medecine.unige.ch.

Momentary fluctuations of baseline activity have been shown to influence responses to sensory stimulation both behaviorally and neurophysiologically. This suggests that perceptual awareness does not solely arise from physical stimulus properties. Here we studied whether the momentary state of the brain immediately before stimulus presentation indicates how a physically unique but perceptually ambiguous stimulus will be perceived. A complex Necker cube was intermittently presented and subjects indicated whether their perception changed with respect to the preceding presentation. EEG was recorded from 256 channels. The prestimulus brain-state was defined as the spatial configuration of the scalp potential map within the 50 ms before stimulus arrival, representing the sum of all momentary ongoing brain processes. Two maps were found that doubly dissociated perceptual reversals from perceptual stability. For EEG sweeps classified as either map, distributed inverse solutions were computed and statistically compared. This yielded activity confined to a region in right inferior parietal cortex that was significantly more active before a perceptual reversal. In contrast, no significant topographic differences of the evoked potentials elicited by stable vs. reversed Necker cubes were found. This indicates that prestimulus activity in right inferior parietal cortex is associated with the perceptual change.

Key Words: bistable perception • functional microstate • high-density EEG • prestimulus activity • weighted minimum-norm inverse solution


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