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

Document Type: 
Article
Article Type: 
Experimental
Disciplines: 
Neuroscience
Topics: 
Neural Correlates of Consciousness
Keywords: 
gamma oscillations, consciousness, visual masking, EEG
Deposited by: 
Michael J S Beaton on 28 January 2009
Date of Issue: 
2009
Authors: 
Jaan Arua, Talis Bachmann
Journal/Publication Title: 
Neuroscience Letters
Volume: 
450
Issue Number: 
3
Page Range: 
351-355
Official URL: 
http://linkinghub.elsevier.com/retrieve/pii/S0304394008016649
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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