International Union for Circumpolar Health Ministry of Public Health and Social Development of RF Russian Academy of Medical Sciences Siberian Branch of Russian Academy of Medical Sciences Siberian Branch of Russian Academy of Sciences Medical Polar Fund “Science” The Northern Forum

Abstracts

Ecology and adaptation (medical ecology)

Seasonal affective disorder (SAD) of winter type is a special form of depression that recur during the winter time and remit in summer. The relationship of depressed states to functional brain asymmetry let suggest that winter depression is characterized by special dysfunction of hemispheric activity. In the present study seasonal variations in hemispheric functions were studied with the help of dual task paradigm (concurrent manual-verbal interference) in normal men and women and in women with SAD and peculiarities of EEG patterns in patients during winter depression and summer remission were determined. Seasonal changers in activity of the right hemisphere were found in men while activity of the both hemispheres changed with seasons in women. In healthy subjects the most pronounced changes in hemispheric activity were found in spring. In contrast, in SAD women profound changes were found in winter. Winter changes manifest themselves as increase of interference in right-hemisphere condition. Compared with control subjects, SAD subjects had lower EEG power in delta, theta, and alpha frequency bands and opposite asymmetry of these rhythms in parietal and temporal regions due to increased EEG power over the right electrode sites in patients and over the left electrode sites in controls. Similar differences between groups were found for frontal asymmetry of the beta power. In comparison with controls, in depressed patients foci of decreased EEG coherence were found in left and right frontal and right posterior regions. Remitted SAD patients showed normalization of EEG power and frontal asymmetry and disappearance of the foci of decreased coherence in anterior areas of the hemispheres. In contrast, the abnormal lateral pattern of EEG power in posterior region remained stable.

Note. Abstracts are published in author's edition

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