The aperiodic and periodic activities of EEG dynamically relate with cognitive performance in schizophrenia

Aperiodic and periodic activities of electrophysiological signals have strong correlation with various neurocognitive factors. In the current study, we aim to investigate the aperiodic exponent and periodic oscillations (alpha and beta band power) and their associations with cognitive performance in schizophrenia (SCZ).

We enrolled 32 SCZ patients and 33 healthy controls (HC) for the study. Cognitive performance was assessed using the total Brief Assessment of Cognition in Schizophrenia (BACS). Before and after the language comprehension tasks (humor, metaphor and irony), the 5-min eyes-closed and eyes-open EEG signals were collected respectively. The aperiodic exponent and periodic power were extracted and obtained according to the division of brain regions. Finally, Pearson correlation was used to examine the relationships between the EEG parameters and behavioral measures.

SCZ participants exhibited higher aperiodic exponents and lower periodic oscillations compared to HC. The aperiodic exponent decreased significantly after the tasks in central location (F (56,1) = 8.93, P = 0.004, η ² = 0.14) in both groups, while the periodic oscillations had no significant change. The variance of the aperiodic exponent showed significantly negative correlation with Z scores of humor comprehension tasks (r = -0.42, P = 0.027) in SCZ. Besides, the pre-tasks aperiodic exponent in posterior location positively correlated with T scores of attention and speed of information processing (r = 0.35, P = 0.048).

Our findings confirmed the higher aperiodic exponent with lower alpha and beta band in SCZ, along with the variability and task-responsiveness of the aperiodic exponent. The findings suggest that aperiodic exponent holds strong cognitive functional implications in SCZ.