Psilocybin's acute perceptual psychedelic effects may arise from drug-level decreases in the occurrence and duration of lateral and medial frontoparietal connectivity motifs. The authors apply and argue for a modified approach to modeling eigenvectors from LEiDA that more fully acknowledges their underlying structure. These findings contribute to a more comprehensive neurobiological framework underlying acute effects of serotonergic psychedelics.
After a psychedelic dose of psilocybin, the occurrence and duration of two brain states involving lateral frontoparietal and medial fronto-parietal-cingulate coherence decrease, while a fully connected brain state increases. These changes are associated with both the level of psilocin in the blood and the intensity of the subjective drug experience. The findings suggest that the acute perceptual effects of psilocybin may arise from a shift away from specific frontoparietal connectivity motifs toward a more uniform connectivity structure. The study also proposes an improved method for modeling brain states from dynamic functional connectivity data.
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.