To See or Not to See: Prestimulus α Phase Predicts Visual Awareness

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 alpha 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 alpha 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 alpha cycle lasting 100 ms, the human brain goes through a rapid…

• NI
  National Institute of Mental Health

  Award: MH080182