Negative symptoms and EEG alpha activity in schizophrenic patients

Quantitative analyses of electroencephalographic (EEG) recordings in schizophrenic patients have often demonstrated reduced alpha band (8-13 Hz) activity. However, this finding is not universal and there is some evidence that subgroups of schizophrenics may differ in overall or lateralized levels of EEG alpha activity. To investigate this issue, the authors examined relationships between clinical ratings performed at the time of EEG recording and resting alpha power and coherence in 14 medication free schizophrenic patients. Nine channels of previously recorded resting (eyes open) EEG were transformed to average reference prior to spectral analysis and transformed to source derivation prior to calculation of inter-electrode coherences. Patients were rated with the Brief Psychiatric Rating Scale (BPRS), from which subscales corresponding to negative symptoms, positive symptoms, paranoia, and anxiety/depression were derived. Ratings and EEG measures were also obtained on 10 of the schizophrenic patients after neuroleptic treatment. Multiple regression with repeated measures was used to examine the influence of the subscale scores on bilateral log alpha power and both within- and between-hemisphere alpha coherence at selected locations. Prior to treatment, negative symptoms varied inversely with alpha power (p < 0.02), within-hemisphere alpha coherence (p < 0.03), and between-hemisphere coherence (p = 0.053). The effect of negative symptoms on alpha power was bilateral, but the effect on within-hemisphere coherence tended (p = 0.053) to be right-sided. After treatment these relationships were no longer present. The possible implications of and the effects of drug treatment on an association between negative symptoms and reduced alpha activity are discussed.