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Prestimulus EEG Power Predicts Conscious Awareness But Not Objective Visual Performance
Christopher S Y Benwell1, Chiara F Tagliabue2, Domenica Veniero1
1Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow G12 8QB, United Kingdom.
Eneuro
|December 20, 2017
Summary
Prestimulus alpha power influences subjective awareness of visual stimuli but not objective accuracy. Ongoing neural activity affects conscious perception differently than task performance, dissociating awareness from sensitivity.
Area of Science:
- Neuroscience
- Cognitive Science
- Psychophysics
Background:
- Prestimulus oscillatory neural activity, particularly alpha (α) power and phase, influences perceptual outcomes in detection and discrimination tasks.
- The precise mechanisms linking baseline neural oscillations to perception, especially the inverse relationship between α power and detection, remain debated, with theories suggesting effects on criterion rather than sensitivity.
Purpose of the Study:
- To investigate whether prestimulus oscillatory power and phase predict trial-by-trial discrimination accuracy and perceptual awareness.
- To differentiate the influence of ongoing neural activity on subjective awareness versus objective visual sensitivity.
Main Methods:
- Electroencephalography (EEG) recorded neural activity in human participants.
- Participants performed a luminance discrimination task on near-threshold visual stimuli.
- Single-trial ratings of perceptual awareness were collected alongside task performance.
Main Results:
- Prestimulus power in the 3-28 Hz range was inversely related to perceptual awareness ratings; lower power correlated with higher awareness.
- Prestimulus power did not predict discrimination accuracy.
- Prestimulus oscillatory phase did not predict either awareness ratings or discrimination accuracy across any frequency band.
Conclusions:
- Prestimulus alpha power modulates subjective awareness of visual stimuli, suggesting it influences conscious perception.
- Prestimulus oscillatory activity, specifically power and phase, does not affect visual sensitivity in discrimination tasks.
- A dissociation exists between the impact of ongoing neural activity on conscious awareness and objective performance, highlighting distinct neural mechanisms.
