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Detecting Pre-Stimulus Source-Level Effects on Object Perception with Magnetoencephalography
Published on: July 26, 2019
Pre- and poststimulus alpha rhythms are related to conscious visual perception: a high-resolution EEG study
Claudio Babiloni1, Fabrizio Vecchio, Alessandro Bultrini
1Dipartimento di Fisiologia Umana e Farmacologia, Università degli Studi di Roma La Sapienza, Rome, Italy. claudio.babiloni@uniroma1.it
Cerebral Cortex (New York, N.Y. : 1991)
|January 10, 2006
Summary
Conscious visuospatial processing is linked to specific alpha brain rhythms. Increased prestimulus alpha power and decreased poststimulus alpha power in certain brain areas correlate with conscious awareness during visuospatial tasks.
Area of Science:
- Neuroscience
- Cognitive Science
- Electrophysiology
Background:
- Visuospatial processing, both conscious and unconscious, is associated with parietooccipital cortical activity.
- Previous research utilized late visual-evoked potentials to understand these processes.
- The role of specific theta and alpha brain rhythms in differentiating conscious from unconscious visuospatial tasks remained unclear.
Purpose of the Study:
- To investigate if distinct patterns of prestimulus and poststimulus theta and alpha brain rhythms characterize conscious versus unconscious visuospatial processing.
- To explore the neural correlates of self-reported visual awareness during a visuospatial task.
Main Methods:
- Electroencephalography (EEG) with 128 channels was used to record brain activity in normal adults.
- Participants performed a visuospatial task involving cue stimuli presented at threshold time for recognition, followed by go stimuli.
- Source analysis of theta and alpha rhythms was performed using low-resolution electromagnetic brain topography software for 'seen' and 'not seen' epochs.
Main Results:
- Prestimulus low-band alpha rhythms (6-10 Hz) showed higher power in frontal, parietal, and occipital areas during trials where the cue was consciously perceived ('seen').
- Poststimulus high-band alpha rhythms (10-12 Hz) in parietal and occipital areas exhibited a greater decrease in power during 'seen' trials compared to 'not seen' trials.
- Alpha rhythm power, both before and after visual stimulation, appears to covary with visuospatial consciousness.
Conclusions:
- Specific patterns of alpha rhythm modulation in both prestimulus and poststimulus phases are associated with conscious visuospatial awareness.
- The findings suggest a facilitatory role of alpha rhythms in conscious visuospatial processing.
- This study provides electrophysiological evidence linking alpha rhythm dynamics to the level of visual consciousness.
