Altered neural dynamics in occipital cortices serving visual-spatial processing in heavy alcohol users.

BACKGROUND: Visual-spatial processing deficits have been previously linked to heavy alcohol use, but the underlying neurological mechanisms are poorly understood. Neuroimaging studies have shown alcohol-related aberrations in occipital cortices that appear to be associated with these neuropsychological deficits in visual-spatial processing, however the neural dynamics underlying this altered processing remains unknown.
METHODS: Twenty-three adults with high scores on the Alcohol Use Disorders Identification Test - Consumption (male: ⩾5, female: ⩾4) were compared to 30 demographically-matched controls with low Alcohol Use Disorders Identification Test - Consumption scores (⩽2). All participants completed a visual-spatial processing task while undergoing high-density magnetoencephalography. Time-frequency windows of interest were determined using a data-driven method, and spectrally-specific neural activity was imaged using a beamforming approach. Permutation testing of peak voxel time series was then used to statistically compare across groups.
RESULTS: Participants with heavy alcohol use responded slower on the task and their performance was more variable. The magnetoencephalography data indicated strong theta (4-8 Hz), alpha (10-16 Hz), and gamma (62-72 Hz) responses in posterior brain regions across both groups. Following voxel time-series extraction, significant group differences were found in the left and right visual association cortices from about 375-550 ms post-stimulus, such that adults with heavy alcohol use had blunted alpha responses compared to controls.
CONCLUSION: Individuals with heavy alcohol use exhibited aberrant occipital alpha activity during visual-spatial processing. These data are the first to show spectrally-specific differences during visual-spatial processing related to heavy alcohol use, and highlight alcohol's effect on systems-level neural activity.