In the present study quantitative EEG analysis was performed in 20 male and 20 female healthy adults in order to examine the gender differences in EEG activity at rest and during photic stimulation. The females generally showed a higher amplitude in the resting EEG than the males, with significant differences observed for the delta, theta, alpha 2 and beta bands at the limited electrode sites. The gender differences were more pronounced in EEG activity during photic stimulation, and the females had a higher EEG amplitude in the frequency band identical or harmonically related to the stimulus frequency. These findings provide further evidence that the gender differences exist in EEG activity in both stimulus and nonstimulus conditions.

In the present study, quantitative EEG analysis was performed at rest and during 10 Hz photic stimulation in 14 drug-naive patients with first-episode paranoid schizophrenia and 20 sex- and age-matched control subjects. Compared with the normal controls, the patients had significantly lower alpha-2 band amplitude in the resting EEG over all recording regions. No significant group differences were found in other frequency bands. In addition, EEG analysis during photic stimulation demonstrated that the patients had a rather uniform topographic profile in EEG amplitude for the alpha band, with significant group differences being confined to the posterior regions in the left hemisphere. There were no significant group differences in the amplitude for the frequency bands harmonically related to the stimulus frequency. These findings provide further evidence that schizophrenic patients have abnormal EEG activity in both non-stimulus and stimulus conditions, and suggest a dysfunction in the mechanisms underlying EEG alpha generation in schizophrenia.

Steady-state visual evoked potentials (steady-state VEPs) from pattern-reversal stimulations were compared in treated schizophrenic patients and normal subjects matched for sex and age. The VEP amplitudes were more variable in the patients than in the controls. Furthermore, the VEP amplitudes of the patients mostly showed little or no change when the check size was varied, in contrast to the controls who showed a marked check size effect. These results suggest that schizophrenics receiving drugs have dysfunction of the visual system, especially an inability to respond adequately to changes of visual information.

The present study was conducted to compare electroencephalogram (EEG) driving responses to 10 hertz photic stimulation in 14 drug-naive schizophrenia patients and 16 sex- and age-matched control subjects. The amplitude of photic driving responses (PDRs) recorded from the occipital region was significantly lower in schizophrenia patients than in controls. In eight schizophrenia patients (vs. none in the control group) the PDR amplitudes recorded at the frontal region were higher than those at the occipital region, and frontal to occipital PDR ratios were significantly larger in schizophrenia subjects than in controls. Quantitative analysis of the resting EEG showed that the patients also had a significantly lower amplitude for the alpha frequency band. These findings suggest that the PDRs of schizophrenia patients are abnormal in their amplitude and distribution.