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bioRxiv · 10.64898/2026.08.23.746502

A dominant frontoparietal beta oscillatory brain state in the days after psilocybin and 5-MeO-DMT

West, C. L.·Baker, B.·Duran, A.·Nadeem, S.·Calhoun, V.·Hamm, J. P.
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Abstract

Background. Serotonergic psychedelics show promise for treating psychiatric disorders, with symptom improvements lasting for weeks after a single dose. Clarifying the neural basis of these effects would benefit from an identification of empirical biomarkers of such lasting shifts in brain function. Resting state EEG offers a rapid (<5 minute), low-cost window into functional brain networks. However, connectivity is not static, but cycles between recurring semi-stable patterns that vary across frequency bands. Here we employed a dynamic function connectivity (dFC) framework to identify frequency-specific connectivity states and examine how they change in the weeks following psychedelic use. Methods. We collected resting-state EEG from individuals who had used one of two serotonergic psychedelic subclasses within the prior three weeks, psilocybin/LSD (typical; n=14) or 5-MeO-DMT (atypical; n=12), and age- and sex-matched controls (n=16). Frequency-band-specific spatial connectivity states (phase-lag index) were estimated across the full sample (5 per band). Groups were compared on proportion and dwell-time (per state) and state-to-state transitions. Results. A right frontoparietally-distributed beta synchrony state was dominant after both typical and atypical psychedelics use (proportion/dwell-time). This effect correlated with the number of days since using psychedelics. A globally-distributed theta-band state was prominent in recent users of typical psychedelics but occurred less often in atypical users. In contrast, neural entropy (Lempel-Ziv complexity; known to increase acutely during psychedelic dosing) was not altered in recent users of either subclass. Conclusion. These results reveal a beta-band signature of altered neural dynamics in the week following a psychedelic dose, consistent with a relaxation of brain network hierarchy after psychedelics.

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West, C. L., Baker, B., Duran, A., Nadeem, S., Calhoun, V., Hamm, J. P.. 2026-08-27. A dominant frontoparietal beta oscillatory brain state in the days after psilocybin and 5-MeO-DMT. https://doi.org/10.64898/2026.08.23.746502

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