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PLoS Biol. 2009 Mar 17;7(3):e61. doi: 10.1371/journal.pbio.1000061.

Converging intracranial markers of conscious access.

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  • 1INSERM, Cognitive Neuro-Imaging Unit, Institut Fédé ratif de Recherche (IFR) 49, Gif sur Yvette, France.

Abstract

We compared conscious and nonconscious processing of briefly flashed words using a visual masking procedure while recording intracranial electroencephalogram (iEEG) in ten patients. Nonconscious processing of masked words was observed in multiple cortical areas, mostly within an early time window (<300 ms), accompanied by induced gamma-band activity, but without coherent long-distance neural activity, suggesting a quickly dissipating feedforward wave. In contrast, conscious processing of unmasked words was characterized by the convergence of four distinct neurophysiological markers: sustained voltage changes, particularly in prefrontal cortex, large increases in spectral power in the gamma band, increases in long-distance phase synchrony in the beta range, and increases in long-range Granger causality. We argue that all of those measures provide distinct windows into the same distributed state of conscious processing. These results have a direct impact on current theoretical discussions concerning the neural correlates of conscious access.

PMID:
19296722
[PubMed - indexed for MEDLINE]
PMCID:
PMC2656551
Free PMC Article
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