Altered neural excitation/inhibition (E/I) balance has long been suspected as a potential
underlying cause for clinical symptoms in schizophrenia (SZ). Recent methodological
advancements linking the spectral slope ( β ) of neurophysiological recordings – such
as them electroencephalogram (EEG) – to E/I ratio provided much-needed tools to better
understand this plausible relationship. Importantly, most approaches treat E/I ratio
as a stationary feature in a single scaling range. On the other hand, previous research
indicates that this property might change over time, as well as it can express different
characteristics in low- and high-frequency regimes. In line, in this study we analyzed
resting-state EEG recordings from 30 patients with SZ and 31 healthy controls (HC)
and characterized E/I ratio via β separately for low- (1–4 Hz) and high- (20–45 Hz)
frequency regimes in a time-resolved manner. Results from this analysis confirmed
the bimodal nature of power spectra in both HC and SZ, with steeper spectral slopes
in the high- compared to low-frequency ranges. We did not observe any between-group
differences in stationary (i.e., time-averaged) neural signatures, however, the temporal
variance of β in the 20–45 Hz regime was significantly reduced in SZ patients when
compared to HC, predominantly over regions corresponding to the dorsal attention network.
Furthermore, this alteration was found correlated to positive clinical symptom scores.
Our study indicates that altered E/I ratio dynamics are a characteristic trait of
SZ that reflect pathophysiological processes involving the parietal and occipital
cortices, potentially responsible for some of the clinical features of the disorder.
