Aberrant hyperfocusing in schizophrenia indicated by elevated theta phase-gamma amplitude coupling

We aimed to investigate electroencephalographic (EEG) markers of aberrant hyperfocusing, a novel framework of impaired selective attention, in schizophrenia patients by using theta phase-gamma amplitude coupling (TGC). Fifty-four schizophrenia patients and 73 healthy controls (HCs) underwent EEG recording during an auditory oddball paradigm. For the standard and target conditions, TGC was calculated using the source signals from 25 brain regions of interest (ROIs) related to attention networks and sensory processing; TGC values were then compared across groups and conditions using two-way analysis of covariance. Correlations of altered TGC with performance on the Trail Making Test Parts A and B (TMT-A/B), were explored. Compared to HCs, schizophrenia patients showed elevated TGC in the left inferior frontal gyrus (IFG) and superior temporal gyrus in the standard condition but not in the target condition. Correlation analyses revealed that the TGC in the left IFG was positively correlated with the TMT-A/B completion times. Aberrant hyperfocusing, as reflected by elevated TGC in attention-related brain regions, was related to behavioral performance on the TMT-A/B in schizophrenia patients. This study suggests that TGC is a electrophysiological marker for aberrant hyperfocusing of attentional processes that may result in cognitive impairments in schizophrenia patients.