The group of liquidators of Chernobyl Nuclear Power Plant accident (n=170) with nonpsychotic mental disorders of exogenic-organic origin was studied. Patients were stratified into five groups on the basis of dominating symptoms in different stages of disorders: group 1 included patients with the prevalence of asthenic symptoms (n=104); group 2 - with the prevalence of autonomous disorders (n=37); group 3 - with the marked neurotic-like symptom complex (n=10); group 4 - with depressive symptoms (n=10); group 5 - with disturbances of cognitive function. The control group included 150 healthy people. Recording and mapping of coherence (COH) of the brain electrical activity was conducted using the apparatus-software complex for topographic mapping of brain electrical activity NEURO-CM (Russia) with the bandwidth from 0 to 40 Hz and the time constant of 0,3 sec. The EEG record was carried out monopolar from symmetrical cortical zones (10-20% scheme). Changes of COH were characterized by staging in patients compared to the controls. In the initial stage of disease, the integrative links were decreased in the temporal cortical zones of the left hemisphere. The reduction of functional activity in temporal-central cortical zones was found that might be the consequence of mesodiencephalic dysfunction. In the later stages, temporal zones of the right hemisphere were mostly affected. The parallel reinforcement of functional activity of occipital zones, in particular, the increase of long links with frontal areas, was noted in the overall formation of the psychoorganic syndrome. This phenomenon may be considered as a compensatory mechanism when the phylogenetically older cortical zones, which are more resistant to pathological changes, become leaders in the realization of integrative brain activity during the development of a pathological state.