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 decomposed fractal and oscillatory BLP in a sliding window manner from resting-state EEG recordings collected in eyes-closed resting-state. The SZ cohort was characterized by elevated baseline of total fractal power (p = 0.0015, |r| = 0.4073), while its temporal variability was comparable between the two study groups. On the other hand, spectral power in the alpha (p < 10^-4, d = 1.0503) and beta (p = 0.0022, |r| = 0.3925) regimes exhibited reduced fluctuation in SZ compared to HC, with no between-group differences in their baselines. Furthermore, alpha variability could be attributed to alterations in isolated oscillatory activity, while variability in beta-BLP over the dorsal attention network was found correlated with negative symptoms in SZ (Spearman r = -0.4994, p = 0.0055). Finally, surrogate data testing indicated altered phase dynamics in SZ as a potential mechanism for diminished BLP fluctuations.