EEG power variation in schizophrenic subgroups: effects of emotionally salient stimuli.

Eighteen unmedicated chronic schizophrenic patients and 13 normal controls were tested in a paradigm designed to examine functional changes in electroencephalographic (EEG) activity following presentation of emotionally salient auditory stimuli and control tones. Five standard bands of EEG spectral power were examined at bilateral frontal and temporal surface recording sites. The schizophrenic subjects were assigned to diagnostic subgroups on the basis of DSM-III-R criteria following independent clinical examination by two staff psychiatrists. Those subjects who met DSM-III-R criteria for paranoid schizophrenia were assigned to one subgroup (PS subgroup), while those who met DSM-III-R criteria for either residual or undifferentiated schizophrenia were assigned to a second subgroup (R/US subgroup). Analysis of Variance of EEG activity recorded at bilateral frontal (F1 and F2) and temporal (T3 and T4) scalp leads revealed significant diagnosis-related differences in alpha and beta-2 activity at temporal recording sites, and in beta-1 and beta-2 activity at frontal recording sites. Post-hoc tests revealed that significant differences in all four measures occurred in the R/US subgroup, which showed a decrease in temporal alpha and an increase in temporal beta-2 power as compared to controls. These variations in EEG activity appeared to demonstrate a degree of subgroup specificity, as the R/US subgroup also differed significantly from the PS subgroup on most of these measures. Significant subgroup-specific lateralization effects were also observed for temporal lobe delta activity and for frontal lobe beta-1 activity. These findings are interpreted in terms of subgroup-specific alterations in the processing of sensory information in schizophrenia, particularly when such information is emotionally salient. They suggest that subgroup differences in emotional and clinical state may be reflected in differential changes in EEG spectra within the schizophrenic population.