Topographical distribution of absolute alpha-power in the EEG and psychopathology in schizophrenic outpatients

In 36 schizophrenic outpatients (Research Diagnostic Criteria) under neuroleptic maintenance treatment the EEG was recorded under resting conditions. The absolute alpha-power (7.5-13 Hz) was estimated by Fast Fourier Transform as the mean of 300 2-second epochs for the leads F3/A1, F4/A2, 01/A2 and 02/A2. Two lateralization quotients (anterior, posterior) and two anteriorization quotients (left, right) were calculated from the absolute alpha-power. Clinical status was assessed cross-sectionally with BRPS, GAS and CGI. The main findings are: 1) A linear relationship between the left/right ratio of absolute alpha-power over posterior regions and anxiety/depression--the more the alpha-power is left-lateralized, the higher the anxiety/depression score; 2) a curvilinear, inverted U-shaped relationship between the left/right ratio of absolute alpha-power over posterior regions and the score of schizophrenia-specific symptomatology; 3) the amount of daily neuroleptic dose (mgCPZ) has no impact on EEG-parameters. Results are discussed with respect to hemisphere asymmetry models of psychopathology.