Asymmetric interhemispheric delta waves during all-night sleep in humans

Objective: In order to better understand the asymmetry of brain function during sleep, period-amplitude analysis of delta EEG activity was performed on polysomnograms (PSGs) in normal humans. Twenty healthy, right-handed male volunteers aged 22-35 years (mean age 27.2 years) served as subjects in this study. Methods: EEGs were recorded from disc electrodes placed at bilateral frontal, central, parietal, occipital, anterotemporal and poster otemporal (10-20 electrode system) sites using A1 + A2 for reference. Period-amplitude analysis was performed by the zero-crossing method using the Medilog Sleep Analyzing Computer. Results: Delta counts in the right frontal and central regions during all-night sleep were significantly greater than in those of the left; total delta counts of the right frontal region were greater than those of the left in 18 of the 20 subjects. There were no significant differences in delta counts between the left and right hemispheres in parietal, occipital, anterotemporal, and postero-temporal regions. Conclusions: These results suggest distinct laterality in the number of delta waves in the frontal and central regions, reflecting functional asymmetry of the brain during sleep. (C) 2000 Elsevier Science ireland Ltd. All rights reserved.