Abnormal aperiodic activity and alpha oscillation in schizophrenia: evidence from magnetoencephalography.

BACKGROUND: Periodic oscillations and aperiodic activity in electrophysiological signals are associated with pathological processes and cognitive performance in neuropsychiatric disorders. This study aimed to investigate the aperiodic activity and alpha oscillations in resting-state magnetoencephalography (MEG) signals in schizophrenia, and their associations with symptoms, cognition, and autobiographical memory. METHODS: Twenty-seven healthy controls and 40 schizophrenia patients were enrolled. Clinical symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Cognitive function and autobiographical memory were respectively evaluated with the MATRICS Consensus Cognitive Battery (MCCB) and the Autobiographical Memory Test (AMT). Resting-state MEG data were acquired. RESULTS: Schizophrenia patients showed increased aperiodic exponent in the bilateral pericalcarine cortex (left: pFDR = 0.020; right: pFDR = 0.027) and the supramarginal gyrus (left: pFDR = 0.025; right: pFDR = 0.025), and reduced alpha peak power compared to healthy controls. Bilateral pericalcarine exponent correlated positively with PANSS positive scores (left: r = 0.33, p = 0.038; right: r = 0.35, p = 0.028), while reduced alpha power in the bilateral posterior cingulate cortex and the left supramarginal gyrus was associated with impairments in verbal learning, visual learning, and autobiographical memory. CONCLUSIONS: Schizophrenia shows increased aperiodic exponent and reduced alpha peak power, with region-specific associations with clinical symptoms, cognitive function, and autobiographical memory. These findings highlight the importance of separating periodic and aperiodic components in neural power spectrum analysis and provide MEG-based evidence supporting the pathophysiological relevance of aperiodic activity in schizophrenia.