Top Highlights

• Psilocybin caused a significant decrease in the positive coupling between the mPFC and PCC. These results strongly imply that the subjective effects of psychedelic drugs are caused by decreased activity and connectivity in the brain's key connector hubs, enabling a state of unconstrained cognition.
• Psilocybin significantly decreased brain blood flow and venous oxygenation in a manner that correlated with its subjective effects, and significantly decreased the positive coupling of two key structural hubs (the mPFC and the PCC).
• The results suggest decreased activity and connectivity in the brain's connector hubs, permitting an unconstrained style of cognition.
• sought to address this question using complementary functional MRI (fMRI) techniques and a protocol designed to image the transition from normal waking consciousness to the psychedelic state
• Two groups of healthy subjects were scanned using arterial spin labeling (ASL) perfusion and blood-oxygen level-dependent (BOLD) fMRI during intravenous infusion of psilocybin. Infused over 60 s (2 mg in 10-mL saline), psilocybin's subjective effects begin within seconds (5), allowing the capture of the corresponding change in brain state.

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