[A dynamic assessment of the reaction of the human brain to radiation exposure (the aftermath of the accident at the Chernobyl Atomic Electric Power Station)].

The present study was aimed at the comparative assessment of electrophysiological and clinical data in persons (155 right-handed men) who took part in the Chernobyl clean-up in different periods after radiation. Dynamic evaluation of psychoneurological disorders revealed the growth of incidence and severity of cerebrovascular disturbances accompanied by the signs of organic symptoms' aggravation and encephalopathy in longer periods after radiation. The results of neuropsychological examination also showed the deterioration of patients' state manifested as growth of fatigue, cognitive defects, and emotional impairments. Analysis of the EEG parameters, including power and coherence mapping and 3-d dipole source localization analysis demonstrated the increasing number of patients with the most severe forms of EEG pathology: the "plane" type in combination with fast paroxysmal (beta-band) and slow forms of activity from 45% in 1990-92 to 63% in 1997. The "hypersynchronization" type of EEG activity was typical for the earlier period accompanied by the dominance of the pathological forms of EEG activity in mediobasal structures of the left hemisphere, and brainstem zones vs. diencephalon and the right hemisphere. The later period was characterized by decreasing coherence in symmetrical frontal and front-temporal areas of the left hemisphere, while in the early period the hypersynchronization prevailed in symmetrical central areas and in the right hemisphere. The evidence were obtained to a disconnection between the brain hemispheres. We suppose that the progressive involvement of structures of the limbic-reticular complex (especially, brainstem, mediobasal structures, and white matter) into the pathological process occurs with time in participants of clean-up of the Chernobyl disaster consequences.