[Modern approaches to the encephalographic diagnosis of non-convulsive status epilepticus].

The article presents modern conceptions on instrumental diagnosis, using electroencephalography, of non-convulsive status epilepticus (NCSE) based on a traditional classification and recommendations of the American Clinical Neurophysiology Society (2012). The descriptive diagnostic parameters for the recognition of different changes in the brain electrical activity in NCSE and their correlations in the structure of traditional and new classifications are presented.

[Gamma-rhythm, positive, negative symptoms and cognitive dysfunction in schizophrenia].

We studied characteristics of gamma-band (30-40 Hz) EEG in dependence on the prevalence of positive or negative symptoms of schizophrenia, taking into account the state of cognitive functions. Twenty patients with ICD-10 diagnosis of schizophrenia, with different disease duration (first episode and duration of more than two years) and 38 healthy people were studied. The presence and intensity of positive and negative symptoms were measured by the PANSS scale and cognitive functions were assessed using neuropsychological tests. Compared to the controls, the gamma-rhythm power was higher in patients with the prevalence of positive symptoms and lower in patients with negative symptoms. The reduced number of coherent relations, in particular, interhemispheric ones, and the absence of gamma-band synchronization in different brain areas were found in patients as well.

Relationship between EEG power and rhythm synchronization in health and cognitive pathology.

We report here studies of comparative measures of spectral density and cortical interactions in EEG rhythms in health and schizophrenia. In healthy subjects, all rhythms were symmetrical and synchronous. In "acute" schizophrenia, unlike the situation in health, there was asymmetry (predominantly right-sided) in the distribution of the spectral power of EEG rhythms. In chronic patients, asymmetry was less marked, though the power of most EEG rhythms was significantly lower than in the other two study groups. "Acute" patients showed a lack of interhemisphere interactions for all rhythms apart from the alpha rhythm, while the number of cortical interactions in chronic patients was rather lower than that in the "acute" patients, though there were significantly fewer than in healthy subjects. In addition, the gamma range showed only one interhemisphere association in the posterior areas. These neurophysiological characteristics may underlie a number of the impairments of mental activity in patients with schizophrenia. These data may also indicate that the linkage between power characteristics and synchronization of EEG rhythms is a necessary condition for normal perceptive and cognitive activity and the organization of behavior.

[Correspondence between spectral power and synchronization of the brain rhythms in the norm and cognitive pathology].

The work is aimed at the study of correlations between the measures of spectral power and cortical interactions of EEG rhythms in healthy subjects and schizophrenic patients ("acute" and chronic cases). All brain rhythms in healthy subjects appeared to be symmetrical and synchronous both in phase and frequency. In "acute" schizophrenics, opposite to healthy subjects, the distribution of cortical activity is asymmetrical, and in the chronic cases, the spectral power of most cortical rhythms is decreased as compared to healthy subjects. In the "acute" patients, interhemispheric connections are absent in all rhythms but alpha. In the chronic patients, the number of cortical connections is slightly higher than in the acute patients; and they are located in the posterior areas in the gamma rhythm. These neurophysiological aberrations evidently underlie the multiple mental activity disorders in schizophrenic patients. Thus, the correspondence between the brain rhythms and their synchronization is a necessary condition for normal perception, emotions and cognition evidently influencing behavior and consciousness.

[Spectral power and cortical interactions in the beta2 rhythm in normal subjects and schizophrenic patients]. / Spektral'naia moshchnost' i vnutrikorkovye vzaimodeistviia po beta2-ritmu v norme i pri zhizofrenii.

Spectral and coherence characteristics of the beta 2 rhythm (20-40 Hz) were compared in patients with acute schizophrenia (the first episode), patients with chronic schizophrenia (disease duration more than two years), and healthy subjects (control group) during cognitive task performance. Examination showed the "excessive" spectral power of this rhythm in the prefrontal cortical areas in patients with acute schizophrenia and its "insufficient" spectral power in all derivations of the right hemisphere in patients with the chronic form as compared to the controls. The similarity of the beta 2 spectral power distribution in different cortical areas measured by covariance method decreased with increase in psychopathologic manifestations. Coherent analysis revealed a substantially lower number of cortico-cortical functional connections in schizophrenic patients than in healthy subjects, absence of interhemispheric connections in patients with acute schizophrenia, and a slight increase in their number if patients with the chronic disease. However, as distinct from the controls revealing many inter- and intrahemispheric connections in all cortical areas, in schizophrenics the interhemispheric connections were observed only in the posterior cortical regions. The results point to a disorder of interhemispheric interaction in schizophrenia.