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Neuroimage. 2014 Nov 1;101:337-50. doi: 10.1016/j.neuroimage.2014.07.024. Epub 2014 Jul 22.

Gamma band activity and the P3 reflect post-perceptual processes, not visual awareness.

Author information

1
Department of Psychology, Reed College, Portland, OR 97202, USA. Electronic address: mpitts@reed.edu.
2
Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA.
3
Department of Psychology, Reed College, Portland, OR 97202, USA.
4
Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA; Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA.

Abstract

A primary goal in cognitive neuroscience is to identify neural correlates of conscious perception (NCC). By contrasting conditions in which subjects are aware versus unaware of identical visual stimuli, a number of candidate NCCs have emerged; among them are induced gamma band activity in the EEG and the P3 event-related potential. In most previous studies, however, the critical stimuli were always directly relevant to the subjects' task, such that aware versus unaware contrasts may well have included differences in post-perceptual processing in addition to differences in conscious perception per se. Here, in a series of EEG experiments, visual awareness and task relevance were manipulated independently. Induced gamma activity and the P3 were absent for task-irrelevant stimuli regardless of whether subjects were aware of such stimuli. For task-relevant stimuli, gamma and the P3 were robust and dissociable, indicating that each reflects distinct post-perceptual processes necessary for carrying-out the task but not for consciously perceiving the stimuli. Overall, this pattern of results challenges a number of previous proposals linking gamma band activity and the P3 to conscious perception.

KEYWORDS:

Attention; Consciousness; Gamma; P3; Task relevance; Visual awareness

PMID:
25063731
PMCID:
PMC4169212
DOI:
10.1016/j.neuroimage.2014.07.024
[Indexed for MEDLINE]
Free PMC Article

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