Positron Emission Tomography and Fluorodeoxyglucose Studies of Metabolic Hyperfrontality and Psychopathology in the Psilocybin Model of Psychosis

Abstract

The effects of the indolehallucinogen psilocybin, a mixed 5-HT₂ and 5-HT₁ agonist, on regional cerebral glucose metabolism were investigated in 10 healthy volunteers with PET and [F-18]-fluorodeoxyglucose (FDG) prior to and following a 15- or 20-mg dose of psilocybin.

Psychotomimetic doses of psilocybin were found to produce a global increase in cerebral metabolic rate of glucose (CMRglu) with significant and most marked increases in the frontomedial and frontolateral cortex (24.3%), anterior cingulate (24.9%), and temporomedial cortex (25.3%). Somewhat smaller increases of CMRglu were found in the basal ganglia (18.5%), and the smallest increases were found in the sensorimotor (14.7%) and occipital cortex (14.4%). The increases of CMRglu in the prefrontal cortex, anterior cingulate, temporomedial cortex, and putamen correlated positively with psychotic symptom formation, in particular with hallucinatory ego disintegration. The present data suggest that excessive 5-HT₂ receptor activation results in a hyperfrontal metabolic pattern that parallels comparable metabolic findings associated with acute psychotic episodes in schizophrenics and contrasts with the hypofrontality in chronic schizophrenic patients.