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Boosting up gamma-band oscillations leaves target-stimulus in masking out of awareness: Explaining an apparent paradox

Authors
Journal
Neuroscience Letters
0304-3940
Publisher
Elsevier
Publication Date
Volume
450
Issue
3
Identifiers
DOI: 10.1016/j.neulet.2008.11.063
Keywords
  • Gamma Oscillations
  • Consciousness
  • Visual Masking
  • Eeg

Abstract

Abstract Boost up gamma-band neuronal oscillations have been interpreted as a correlate of pertinent stimulus awareness. The validity of this observation-based conclusion can be rigorously tested if the basic methodological rule of investigating neural correlates of consciousness (NCC) is followed: the varying contents of consciousness should be contrasted with invariant stimulation. We asked whether reliable gamma-band oscillations recorded from primary visual cortex appear as signatures of target awareness in metacontrast masking with invariant stimulation parameters. Surprisingly, clear target-stimuli awareness was associated with less expressed gamma power. However, because when target awareness was effectively masked more gamma power of the EEG response was found, and because this gamma-boost emerged at the post-target time when mask information was presented, we were able to explain our results as target substitution in consciousness by mask representation due to enhanced mask processing.

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