Aberrant theta-gamma frequency coupling in patients with first episode psychosis

Abstract

Background: Although cognitive dysfunction has been suggested as one of the core pathologies of schizophrenia and affects patients daily functioning and quality of life, little is known about its neurobiological underpinnings, which would lead to and instigate the development of effective treatment methods. Since the resting-state activity is crucial for cognitive functioning and electroencephalography (EEG) can reflect moment-by-moment changes of neural activity with high temporal resolution, I aimed to investigate theta phase-gamma amplitude coupling (TGC) of resting-state EEG and its relationship with cognitive functioning in patients with first episode psychosis (FEP). Methods: A total of 59 FEP patients and 50 healthy controls (HCs) participated in the resting-state EEG recording in eyes-closed state. In addition to the assessment of severity of clinical symptoms, the Trail Making Test Part A (TMT-A) and Part B (TMT-B), and the California Verbal Learning Test (CVLT) were used to measure cognitive functioning. The TGC from standardized low-resolution brain electromagnetic tomography (sLORETA) source signal of resting-state EEG was calculated in the default mode network (DMN)-related brain regions and was compared between the FEP and HC groups. Correlation analyses to reveal the relationship between TGC in FEP patients and the performance of neurocognitive function tests (NCFTs) were conducted. Results: Mean resting-state TGC was larger for the FEP group than for HCs. Patients with FEP showed greater TGC in the left posterior cingulate cortex (PCC), which was correlated with better performances in TMT-A and TMT-B, and with the immediate and delayed recall of the CVLT. Conclusion: Larger TGC in the brain regions comprising DMN in the FEP group compared to HCs indicates that patients with FEP may show compensatory hyperactivation of DMN-related brain regions during the resting-state, which may be related with reallocation of cognitive resources for preparing cognitive execution. This study not only highlights the moment-by-moment neural underpinnings of cognitive dysfunction in FEP patients but also provides useful background and insight in developing treatment methods for cognitive dysfunction of schizophrenia.