Schizophrenia and spectral analysis of the visual evoked potential.

Power spectral analysis was performed on the visual evoked potentials (VEPs) recorded in response to flashes of different intensity in both unmedicated schizophrenic and normal subjects. At occipital locations (O1, O2), schizophrenics showed less power than normals in the 10-14 Hz frequency range. In the 18-22 Hz range, schizophrenics showed under-activation in the left hemisphere and over-activation in the right. At temporal locations (T3, T4), schizophrenics showed abnormal (left greater than right) hemisphere patterns of activation in 10-14 Hz and 18-22 Hz ranges. There were no group differences in relationships between power and intensity changes at vertex (Cz). The results suggest abnormal cortical-subcortical interactions during analysis of visual information in schizophrenia.