Symptom profile and “gamma” processing in schizophrenia

Abstract

Background. Gamma electrical rhythms (at 40 cycles per second) are postulated to have an important role in relation to the “binding problem” (of how the brain integrates its diverse neuronal activity). Impaired integration of brain activity may be a core pathophysiological feature of schizophrenia. The focus of this study was the examination of within-sample relationships between three primary schizophrenic syndromes (Psychomotor Poverty, Disorganisation, and Reality Distortion) and induced Gamma activity in an auditory target detection paradigm. Method. A time series was constructed of all Gamma activity (extracted from the same data traditionally acquired for Event Related Potentials; ERPs). Data was examined in response to 40 target and 40 nontarget auditory stimuli, in 35 patients with schizophrenia and 35 age- and gender-matched normal controls. Results. Although schizophrenics as a group showed generally reduced Gamma activity, each syndrome was differentiated by a distinct pattern of Gamma disturbance across target and nontarget stimuli. Reality Distortion was correlated with increased Gamma and Psychomotor Poverty with decreased Gamma activity to target stimuli, whereas Disorganisation was correlated with reduced Gamma activity to nontarget stimuli. Conclusions. Gamma activity might elucidate disturbances in integrated brain function, and provide complementary insights to the established slower frequency ERP dysfunctions in schizophrenia. This is the first report of distinctive patterns of Gamma activity in the three schizophrenic syndromes.