Multivariate EEG power spectral analysis in acute schizophrenics.

The electroencephalogram (EEG) during information processing is influenced by specific changes in brain electrical activity. Based on the theory of disturbed information processing in schizophrenics, we analysed auditory stimulus induced EEG changes by Fast Fourier Transformation. The most important of the significant stimulation-dependent EEG power changes were measured in the 0.5-3.5 Hz and 10-13.5 Hz frequency bands in the left frontoparietal lead. In a multivariate analysis the separation of the subjects examined into acute schizophrenics and normals was incorrect in only 21% of the cases (resubstitution rate); using pi-method an error of 31% was estimated.

Repeated acoustic stimulation of acute schizophrenic patients and the habituation of EEG power changes.

Habituation in psychiatric patients to repeated stimuli has typically been described in connection with the measurement of the skin conductance orienting response. Here EEG power spectra of acute schizophrenic patients and normals to 4 trials of an acoustic stimulation were examined for evidence of habituation. In response to stimulation the alpha EEG reactivity was less distinct in schizophrenics than in normals. This is in agreement with the theory of hypovariability or hyperstability of the EEG in schizophrenics. Signs of habituation in acute schizophrenics were clearer in fast beta frequencies of the parietal leads.