title: Gamma band activity and the P3 reflect post-perceptual processes, not visual awareness.
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.
authors: Department of Psychology, Reed College, Portland, OR 97202, USA. Electronic address: mpitts@reed.edu.
authors: Michael A
authors: MA
authors: Pitts
authors: Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA.
authors: Jennifer
authors: J
authors: Padwal
authors: Department of Psychology, Reed College, Portland, OR 97202, USA.
authors: Daniel
authors: D
authors: Fennelly
authors: Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA; Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA.
authors: Antígona
authors: A
authors: Martínez
authors: Department of Neurosciences, University of California San Diego, La Jolla, CA 92093, USA.
authors: Steven A
authors: SA
authors: Hillyard
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D001364:Awareness / Q000502:physiology*; D003243:Consciousness / Q000502:physiology; D004569:Electroencephalography / Q000379:methods*; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Attention; Consciousness; Gamma; P3; Task relevance; Visual awareness