Generalized Slowing of Resting State Neural Oscillations in People with Schizophrenia.

Background: Recent interest in how neural oscillations reflect the flow of information through the brain has led to partitioning electroencephalography (EEG) recordings into periodic (i.e., oscillatory) and aperiodic (i.e., non-oscillatory) components. While both contribute to conventional measures of power within the frequencies that compose EEG recordings, the periodic aspect characterizes true oscillations - the speed of which is thought to be critical to efficient functioning of neural systems. Given evidence of EEG power abnormalities in schizophrenia, we sought to determine if the periodic aspect of EEG was aberrant in people with schizophrenia (SCZ) and could serve as a general measure of brain efficiency.

Methods: Resting state EEGs were gathered from 104 SCZ and 105 healthy control participants. We used the fitting-oscillations-and-one-over-f (FOOOF) toolbox to remove aperiodic neural activity. We computed the cross-correlation between power spectra for individual participants and the mean power spectrum for all participants to quantify the relative speed of neural oscillations.

Results: Periodic activity in SCZ was shifted toward lower frequencies compared to control participants during eyes closed rest. On average SCZ had a 0.55 Hz shift toward oscillatory slowing across the frequency spectrum which predicted worse perceptual reasoning. Slower neural oscillations were associated with weaker perceptual reasoning within SCZ.

Conclusions: Slowed periodic activity at rest is evident in schizophrenia and may represent inefficient functioning of neural circuits as reflected in worse perceptual reasoning. A slower pace of neural oscillations may be a general limitation on the transmission of information within the brain.