Diminished Variability of Alpha and Beta Band-limited Power as a Neural Signature in Schizophrenia

Spectral features of the electroencephalogram (EEG) are essential for providing clinically relevant biomarkers in schizophrenia (SZ). Despite literature indicating altered short-scale neural dynamics in SZ, however, band-limited power (BLP) indices are rarely assessed in a time-resolved manner. To address this, here we evaluated static and dynamic BLP indices in a sample of 30 SZ patients and 31 healthy control (HC) individuals. Guided by recent findings on power spectral dynamics in SZ, we estimated total, and also decomposed fractal and oscillatory BLP in a sliding window manner from resting-state EEG recordings collected in eyes-closed (EC) resting-state. The SZ cohort was characterized by elevated baseline (mean over time) relative power in lower frequency regimes (delta, theta), mainly attributable to aperiodic fractal activity. In the higher regimes (alpha, beta), however, baseline was similar to HC with instead a widespread lessening in temporal fluctuations of both fractal and oscillatory activity. Variability in beta-BLP over the dorsal attention network was found correlated with negative symptoms in SZ. Finally, surrogate data testing indicated a loss of nonlinearity in neural dynamics as a potential mechanism for diminished BLP fluctuations.