Auditory hallucinations in healthy individuals are associated with altered dopamine function in the brain. Using [18F]-DOPA PET imaging, the study found that healthy people who experience auditory hallucinations show differences in dopaminergic activity compared to those who do not, suggesting that dopamine dysfunction may be a trait marker along the psychosis spectrum. The findings indicate that even in the absence of a clinical diagnosis, hallucination proneness is linked to measurable neurochemical variations.
A single dose of THC, the main psychoactive ingredient in cannabis, increases blood flow (perfusion) in brain regions linked to the salience network—the bilateral insula, medial superior frontal cortex, and left middle orbital frontal gyrus—while decreasing connectivity between that last area and the precuneus. The perfusion increase in the left insula correlated with subjective changes in perception and relaxation. Genetic variation in the COMT Val158Met genotype modulated these effects: only Val/Met heterozygotes showed increased perfusion in the executive network after THC, suggesting that prefrontal dopamine levels influence susceptibility to cannabis's acute effects.