Physical aspects of the EEG in schizophrenics

Physical and dynamic aspects of the electroencephalogram (EEG) were evaluated in 12 schizophrenic patients and 12 matched healthy control subjects by means of two descriptive measures proposed by Hjorth (complexity and mobility) and by a nonlinear measure, dimensional complexity. These measures were compared to power spectra analyses. EEG was recorded from frontal, central, and parietal leads under resting conditions (eyes open and eyes closed) for 12 epochs each of 25 sec. Patients showed the expected increased activity in the 1-7 Hz band and, furthermore, a scalp distribution of dimensional complexity and Hjorth complexity opposite to the distribution in controls: in patients dimensional complexity yielded higher values at frontal (Fz) than central (Cz) leads, whereas the resemblance to sinusoidal waveshape (Hjorth complexity) was larger at Fz than Cz. Results indicate more dynamic complexity or variables determining the dynamics of brain processes in frontal areas in patients.