Alterations in temporal-spatial brain entropy in treatment-resistant depression treated with nitrous oxide: Evidence...

Entropy analysis can quantify the dynamic states of the brain and reflect its information processing capacity. Nitrous oxide has shown rapid antidepressant effects in treatment-resistant depression (TRD) patients, but its biomarkers are not yet established.

We recruited 44 TRD patients and randomly assigned them to two groups: one received a 1-hour nitrous oxide inhalation treatment, while the other received a placebo. Resting-state EEG (rs-EEG) scans were conducted at baseline and 24 h post-treatment. A novel approach based multivariate multiscale entropy (MMSE) was employed to analyze temporal-spatial brain entropy (ts-BEN) across four hierarchical brain regions.

TRD patients exhibited significant time-dependent increases in BEN in the frontal lobe region (sensor space: time scales 5-10; source space: time scales 1-5), changes not previously observed. Temporal-spatial BEN correlated with the severity of TRD symptoms and treatment efficacy, indicating adaptive adjustments in brain resting states.

MMSE offers a novel supplementary method for rs-EEG BEN analysis, quantifying the sensitivity of ts-BEN in monitoring nitrous oxide treatment effects. Changes in frontal region ts-BEN may serve as potential biomarkers for TRD and its treatment outcomes.

Our findings enhance the understanding of the physiological mechanisms underlying nitrous oxide treatment for TRD, aiding in clinical diagnosis.