Defects of Gamma Oscillations in Auditory Steady-State Evoked Potential of Schizophrenia.

Background: Patients with schizophrenia have many cognitive deficits. Gamma oscillations exist in the human brain and are closely related to neurocognition. Auditory Steady-State Responses (ASSRs) is an electroneurophysiological index that could reflect gamma oscillations. It was found that the energy evoked by 40 Hz ASSRs in schizophrenic patients was significantly lower than that in healthy subjects. However, the correlation between ASSRs phase index and clinical symptoms and neurocognitive deficits has yet to be systematically studied. The purpose of this study was to investigate the dysfunction of neural activity of gamma rhythmdys function and its association with clinical symptoms and neurocognition in patients with schizophrenia.

Aims: To compare and verify the difference in energy and phase coherence of 20 Hz and 40 Hz ASSRs between schizophrenia and healthy participants, and to explore the correlation between schizophrenia ASSRs and neurocognitive deficits.

Method: Auditory steady-state evoked potentials by repeated auditory stimuli in 24 patients with schizophrenia and 30 healthy controls were recorded. The Positive and Negative Syndrome Scale (PANSS) was used to assess the clinical symptoms of the patients. MATRICS Consensus Cognitive Battery (MCCB) was used for the assessment of neurocognitive function. The correlation between indices, such as ASSRs energy, phase locking factor and phase coherence, and clinical and cognitive assessment was also systematically compared between two groups.

Results: Compared with the control group, the patient group had differences in cognitive domains including information processing speed (t=-2.39, p=0.021), attention/vigilance (t=-2.36, p=0.023), verbal learning (t=-3.11, p=0.003), and reasoning and problem solving (t=-2.60, p=0.012). The energy of 40 Hz ASSRs in the patient group was significantly lower than that in the control group (t=-2.291, p=0.032), and their phase locking factor and inter-trial phase coherence index were lower than control group (t=-3.017, p=0.004 and t=3.131, p=0.003), which was also significantly correlated to reasoning and problem solving function deficits.

Conclusion: Patients with schizophrenia had defects in multiple cognitive domains, and their 40 Hz ASSRs energy was low. Specifically, their phase locking characteristics and phase coherence were poor, which was to some extent related to reasoning ability and thinking disorder.