[Dynamics of neurocognitive functioning in patients in early stages of schizophrenia and schizophrenia spectrum disorders].

The purpose of the study was to assess the dynamics of neurocognitive functioning in patients with the first episode of schizophrenia and schizophrenia spectrum disorders at baseline and in 5-year follow-up. The total number of patients was 67. The severity of symptoms was measured with the PANSS. Cognitive functioning was assessed with the Cognitive Processes Assessment Scale which is based on the methodological approaches developed by A.R. Luria. The liability of cognitive impairment with a tendency to decrease in severity was found in patients with a single psychosis or a history of few psychoses (n=25). In patients with more severe progression of disease (n=33), some labiality of cognitive impairment was observed as well, but, as opposed to the first group, its severity was increasing during the whole 5-year follow-up period. The most severely ill patients with early onset and the most progressive course of the disease (n=9) demonstrated the most severe cognitive impairment, which remained stable along the follow-up. In conclusion, the data obtained present the neurocognitive deficit in schizophrenia and schizophrenia spectrum disorders as not an unchangeable phenomenon, with its dynamics corresponding to regularities of the disease course and its progression.

[Analysis of event-related potentials to verbal stimuli in healthy subjects and schizophrenia patients].

In 30 healthy subjects and 32 patients after the first episode of schizophrenia 19 channel-EEG was recorded during visual presentation of a random sequence of words and pseudo-words. In the first series of the experiments, subjects had to read the presented verbal stimuli, in the second series they had to press a button when seeing a word, and in the third series they were instructed to press the button when seeing a pseudo-word. We studied components N170, P300 and N400. In the group of healthy subjects, the amplitude of N170 increased to words in the situation of their relevance, which corresponds to the "recognition potential", whereas in the group of patients, the amplitude of N170 increased to pseudo-words when they were relevant. So it was a paradoxical response. The amplitude of the ERP later waves (P300 and N400) in the group of schizophrenic patients was smaller and the relevance effect was impaired when the target stimuli were pseudo-words. However, the incongruity effect consisting in an increase in N400 amplitude to a non-target stimulus remained intact in patients.

[Temporal characteristics of the initial stage of the verbal information processing in healthy subjects and in schizophrenia].

The study aimed to investigate the early coding of visually presented words and pseudowords using event-related potentials (ERP). We conducted comparative analysis of the characteristics of P100 and N170 in healthy controls and in patients with the first episode of schizophrenia during passive perception of verbal stimuli as well as under conditions of relevant words and pseudowords. The latency of early ERP components P100 and N170 appeared to be shorter in comparison with healthy subjects in the temporal, parietal and occipital areas. The latency of P100 in patients was significantly shorter in the temporal, parietal and occipital areas, whereas the latency of N170 was shorter in the parietal and occipital areas than in controls. The latency of N170 in healthy subjects was significantly longer to words than to pseudowords and in patients - vice versa. The latencies of N170 in all TPO areas were equal in healthy subjects during word processing, and this equality was upset during non-word processing. In patients with schizophrenia the equality was upset, but, opposite to healthy patients, the upset of equality was more expressed during words processing. Thus, the early stage of verbal information processing in schizophrenic patients is insufficient in time. The time deficit of the automatic processes may lead to defective processing of overall information.

[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.