Psilocybin acutely reduces low-frequency BOLD power and frequency-specific connectivity
bioRxiv April 13, 2026 Anders S. Olsen, Kristian Larsen, Drummond E-W. McCulloch et al.
Psilocybin, a serotonergic drug, alters brain function and connectivity as measured with fMRI, but whether these effects are frequency-specific was unknown. In 28 healthy volunteers scanned after oral psilocybin (0.2–0.3 mg/kg), psilocin (the active metabolite) was associated with a selective reduction in low-frequency spectral power (0.01–0.06 Hz) and an increase in spectral entropy, with strongest effects in transmodal networks. Low-frequency connectivity energy explained by the unimodal/transmodal axis also decreased. These findings demonstrate that psilocin induces spatially distributed, frequency-dependent alterations, suggesting broadband fMRI analyses may obscure low-frequency dynamics and that frequency-resolved approaches offer greater sensitivity.