AUTONOMIC NERVOUS STATUS AND BIOELECTRIC BRAIN ACTIVITY IN ADOLESCENTS-INHABITANTS OF THE POLAR NORTH

Background: Northern European areas are differing in degree of extreme climatic conditions in the Polar and Subpolar latitudes. Formation of the nervous system in adolescents most of all is affected by these adverse climatic factors. Objective: The aim was to study of the autonomic regulation of cardiac activity and brain bioelectric activity in adolescents-inhabitants of the North depending on these autonomic nervous tones. Methods: 300 adolescents (male and female) aged 15–16 years living in the Polar (67°40' N) and Subpolar (64°30' N) northern regions of Russia are examined. Assessment of autonomic nervous tone was determined by the heart rate variability (HRV) and blood pressure parameters. After the initial analysis of these indicators, all subjects in both areas were further divided into groups with vagotonic, normotonic and sympathotonic types. Electroencephalogram (EEG) was recorded in the state of quiet wakefulness with closed eyes (16 standard monopolar leads). EEG characteristic were performed on the values of the amplitude and the index in each frequency band. All described changes were statistically significant at p <0,05–0,001. Results: According HRV and central hemodynamics among adolescents of the Polar North revealed an increase the proportion of individuals with a predominance of sympathetic influences on cardiac activity (37,3%) and significant decrease the proportion of persons with a predominance of vagal influences (10%). A high activity of diencephalic subcortical brain structures in groups of normotonic and sympathotinic persons in the Polar region was revealed, which manifests itself in the form of increased levels of theta and alpha EEG-activity, as well as increased occurrence hypersynchronous EEG-types (50%). In adolescents-inhabitants of the Subpolar region occurs more intensive age optimization of neural processes then in adolescents-inhabitants of the Polar region. Conclusion: The predominance of sympathetic effects on the cardiac activity and higher activity of diencephalic subcortical brain structures in adolescents of the Polar region were revealed.