RT Journal Article
SR Electronic
T1 Synchronization of Neural Activity across Cortical Areas Correlates with Conscious Perception
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2858
OP 2865
DO 10.1523/JNEUROSCI.4623-06.2007
VO 27
IS 11
A1 Lucia Melloni
A1 Carlos Molina
A1 Marcela Pena
A1 David Torres
A1 Wolf Singer
A1 Eugenio Rodriguez
YR 2007
UL http://www.jneurosci.org/content/27/11/2858.abstract
AB Subliminal stimuli can be deeply processed and activate similar brain areas as consciously perceived stimuli. This raises the question which signatures of neural activity critically differentiate conscious from unconscious processing. Transient synchronization of neural activity has been proposed as a neural correlate of conscious perception. Here we test this proposal by comparing the electrophysiological responses related to the processing of visible and invisible words in a delayed matching to sample task. Both perceived and nonperceived words caused a similar increase of local (gamma) oscillations in the EEG, but only perceived words induced a transient long-distance synchronization of gamma oscillations across widely separated regions of the brain. After this transient period of temporal coordination, the electrographic signatures of conscious and unconscious processes continue to diverge. Only words reported as perceived induced (1) enhanced theta oscillations over frontal regions during the maintenance interval, (2) an increase of the P300 component of the event-related potential, and (3) an increase in power and phase synchrony of gamma oscillations before the anticipated presentation of the test word. We propose that the critical process mediating the access to conscious perception is the early transient global increase of phase synchrony of oscillatory activity in the gamma frequency range.