RT Journal Article
SR Electronic
T1 To See or Not to See: Prestimulus α Phase Predicts Visual Awareness
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2725
OP 2732
DO 10.1523/JNEUROSCI.3963-08.2009
VO 29
IS 9
A1 Kyle E. Mathewson
A1 Gabriele Gratton
A1 Monica Fabiani
A1 Diane M. Beck
A1 Tony Ro
YR 2009
UL http://www.jneurosci.org/content/29/9/2725.abstract
AB We often fail to see something that at other times is readily detectable. Because the visual stimulus itself is unchanged, this variability in conscious awareness is likely related to changes in the brain. Here we show that the phase of EEG α rhythm measured over posterior brain regions can reliably predict both subsequent visual detection and stimulus-elicited cortical activation levels in a metacontrast masking paradigm. When a visual target presentation coincides with the trough of an α wave, cortical activation is suppressed as early as 100 ms after stimulus onset, and observers are less likely to detect the target. Thus, during one α cycle lasting 100 ms, the human brain goes through a rapid oscillation in excitability, which directly influences the probability that an environmental stimulus will reach conscious awareness. Moreover, ERPs to the appearance of a fixation cross before the target predict its detection, further suggesting that cortical excitability level may mediate target detection. A novel theory of cortical inhibition is proposed in which increased α power represents a “pulsed inhibition” of cortical activity that affects visual awareness.