A PET-MRI study in seven healthy volunteers found that LSD increases cerebral blood flow while reducing global brain connectivity, with effects linked to 5-HT2A receptor occupancy.

The Nature Neuroscience study used simultaneous PET-MRI to examine LSD in seven healthy volunteers, finding increased global cerebral and internal carotid artery blood flow alongside reduced global brain connectivity. It also identified an anticlockwise hysteresis between plasma LSD levels and subjective effects, and compared LSD with psilocybin in a separate cohort of 25 participants.