[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.