"Gamma (40 Hz) phase synchronicity" and symptom dimensions in schizophrenia

Introduction: The failure of integrative brain function is a fundamental characteristic of schizophrenia. Synchronous Gamma (40 Hz) activity, proposed as a candidate mechanism underlying the integration (“binding”) of distributed brain activities, may provide a direct window into schizophrenic disintegration. Methods: 40 schizophrenia and 40 age/gender-matched control subjects participated in an auditory oddball paradigm. We examined both early (Gamma 1) and later Gamma (Gamma 2) phase synchrony to target stimuli. Factor analysis scores were used to examine the associations between Gamma synchrony and three syndromes (Psychomotor Poverty, Reality Distortion, and Disorganisation). Results: Multiple analyses of variance revealed an overall decrease in frontal and left hemisphere Gamma synchrony, but increased posterior Gamma 2 synchrony in schizophrenia compared to controls. Schizophrenia syndromes were differentiated by distinct patterns of Gamma disturbances: Psychomotor Poverty showed decreased left hemisphere synchrony; Reality Distortion was associated with increased right synchrony; Disorganisation showed a widespread enhancement with a delay in frontal Gamma synchrony. Conclusions: These findings are consistent with previous evidence for left hemisphere and frontal disturbances in the schizophrenia group. However, the syndrome results point to more distinctive patterns of dysregulation in network integration: widespread and excessive in Disorganisation, localised and enhanced in Reality Distortion, versus localised and diminished in Psychomotor Poverty.