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

Authors

Kyle E. Mathewson, University of Illinois at Urbana-Champaign
Gabriele Gratton, University of Illinois at Urbana-Champaign
Monica Fabiani, University of Illinois at Urbana-Champaign
Diane M. Beck, University of Illinois at Urbana-Champaign
Tony Ro, CUNY Graduate CenterFollow

Document Type

Article

Publication Date

3-4-2009

Abstract

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.

Comments

This article was originally published in Journal of Neuroscience, available at https://doi.org/10.1523/JNEUROSCI.3963-08.2009

This work is distributed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).