[Diurnal changes of alpha-rhythm in endogenous depressions]

The aim of the study was to find the diurnal changes in the EEG alpha-activity in patients with endogenous depressions. Both morning and evening EEG records were characterized by the transition of modal value of leading rhythm into the lower frequency band (9-10 Hz versus 10-11 Hz in healthy people). The spectral power of alpha-rhythm was higher, especially in the occipital cortical areas, in the morning hours than in the evening. In the morning, the intrahemispheric differences in the alpha-rhythm power in occipital areas were leveled out while in the evening hours, the normalization of intrahemispheric balance with higher power of alpha-rhythm in the right occipital area was seen. A comparative analysis of mean values of coherence (COH) in cortical areas in patients revealed higher COH values in parietal-central areas of both hemispheres, as well as in frontal- and right middle temporal areas, in the morning compared to those in the evening. COH values were lower in the morning than in the evening in occipital and posterior temporal areas. The mean COH value of alpha-rhythm in the right hemisphere was higher compared to the left hemisphere both in the morning and in the evening.