Gamma-Band Deficits in Response to Standard Stimuli During an Oddball Paradigm in Patients With Schizophrenia

Abstract

Objectives Schizophrenia is characterized by widespread perceptual impairments, including deficits in basic sensory processing. Mismatch negativity reduction is a robust neurophysiological marker of these deficits. While previous research has focused on lowfrequency abnormalities, this study aimed to investigate gamma-band responses to standard auditory stimuli in patients with schizophrenia, hypothesizing that gamma oscillatory activity would be diminished compared to healthy controls. Methods A total of 68 patients diagnosed with schizophrenia or schizoaffective disorder and 38 healthy controls participated. Auditory oddball paradigms were administered while electroencephalography data were recorded. Event-related potentials (ERP) and event-related spectral decomposition (ERSD) were conducted to evaluate evoked power, single-trial power and inter-trial coherence (ITC) in response to standard stimuli. Statistical comparisons between groups were performed using t-tests, and multiple regression analyses examined associations between neurophysiological measures and clinical variables. Results No significant differences were found between groups in P1 latency or amplitude in ERP analyses. However, ERSD revealed that schizophrenia patients exhibited significant reductions in evoked gamma power (t=2.755, p=0.008, d=0.628), single-trial gamma power (t=2.258, p=0.026, d=0.457), and ITC (t=2.151, p=0.036, d=0.507) compared to controls. Multiple regression analyses showed no significant influence of clinical variables on these neurophysiological measures. Conclusions These findings demonstrate that individuals with schizophrenia show marked reductions in both gamma-band power and phase coherence in response to standard auditory stimuli, suggesting impaired formation of mnemonic templates essential for change detection. Disrupted gamma oscillatory activity may underlie perceptual dysfunctions and contribute to the pathophysiology of schizophrenia. Further research examining cross-frequency coupling and its clinical implications is warranted