Asymmetrical Electroencephalographic Change of Human Brain During Sleep Onset Period

OBJECTIVE: Human cerebral hemisphere is known to function asymmetrically with daytime left hemisphere superiority in most right-handed persons. It may have relevance to the localization of specific function of the brain. This study attempted to reveal whether the functional cerebral asymmetry in the wakeful state is still maintained throughout the sleep onset period. METHODS: Thirty-channel EEG was recorded in 61 healthy subjects. The EEG power spectra of each of the seven frequencies were compared between the two kinds of 30-second states; the wakeful stage and the late-sleep stage 1. RESULTS: The asymmetrical indices of sleep stage 1 at several fronto-central leads were decreased in the delta, theta, alpha-2, and all beta bands. Conversely, at parts of parieto-occipital leads showed an increase in the indices of the theta, alphas, beta-1, and beta-2 bands. Any fronto-central leads did not show an increase in the index, and no parieto-occipital leads showed a decrease. CONCLUSION: During the sleep onset period, power spectral asymmetry of the brain showed a different pattern from the wakeful stage. This asymmetrical pattern of EEG powers may suggest a reversal of the left hemispheric dominance during sleep.

EEG analysis of army recruits and veterans and the relationship of the frequency spectrum with depression scale scores / 中华物理医学与康复杂志

Objective To explore the characteristics of EEG frequency in recruits and veterans and their relationship with depression scale scores.Methods Fifty-five newly enlisted soldiers formed the recruits group and 68 demobilized soldiers the veterans group.A general information survey,EEGs and the Hamilton depression scale (HAMD) were administered to all of the subjects.According to the HAMD scores,35 of the 123 were designated as the abnormal group,while 88 formed the normal one.Eighteen of the 35 with EEG abnormalities served as a doubleabnormal group to be compared with the remaining 17 cases with abnormal HAMD scores and normal EEGs (the single-abnormal group),and 9 of the 18 with higher HAMD scores as the higher group,and the other 9 cases as the lower group.The EEG frequency spectrum and the power percentages from the δ to γ frequency bands were calculated as δ:0.5-4 Hz,(o):4-8 Hz,α:8-13 Hz,β:13-25 Hz,γ:25-40 Hz.Results Forty-six of the subjects (37.4％) had abnormal EEG results,35 had abnormal HAMD scores,and 18 (51.4％ of the soldiers with abnormal HAMD scores) had both abnormalities.The veterans had lower δ band power percentage in all channels than the recruits,but in the (0) band it was the reverse.In the left channels the veterans had lower α and γ band power percentages than the recruits.Compared with the normal,all channels in the EEGs of subjects with abnormal HAMD scores had significantly higher δ band power percentages.The higher the δ band power percentage a subject had,the higher his HAMD score.Conclusion There is some correlation between changes in EEG power percentages and the possibility and severity of depression.Objective and subjective EEG evaluation can help improve the positive rate of diagnosis,and thus the management of the army.