DYNAMICAL ASPECTS OF THE EEG IN DIFFERENT PSYCHOPATHOLOGICAL STATES IN AN INTERVIEW SITUATION - A PILOT-STUDY

Dynamical brain states can be characterized by non-linear measures of EEG. The present study shows that critical transitions, i.e., abrupt c hanges from one dynamic pattern of neural mass activity to another one ; may be detected by abrupt variations in local chaoticity. Using an a mbulatory device, EEG was recorded from 10 patients with a schizophren ic and two patients with an affective disorder during a series of 25-m in interviews. Dynamical aspects? in particular, phase transitions in the EEG-dynamics of the EEG were characterized by means of a measure t hat continuously estimates the chaoticity of the EEG signal and is thu s related to its predictability. Results indicate simpler dynamics of the EEG time series in paranoid-hallucinatory patients, while at the s ame time these patients tended to exhibit more abrupt transitions/unit of time between different dynamical EEG states. Such sudden phase tra nsitions in brain activity were significantly enhanced prior to expres sions of thought disorders that were detected by the interviewer and a n observer in the conversation, compared with time periods during the interview without such symptoms. (C) 1997 Elsevier Science B.V.