Long-term use was associated with thinning of the posterior cingulate cortex , thickening of the anterior cingulate cortex , and decreased neocortical 5-HT2A receptor binding .
Despite the high method ological heterogeneity and the small sample sizes , the results suggest that hallucinogens increase introspection and positive mood by modulating brain activity in the fronto-temporo-parieto-occipital cortex
Serotonergic hallucinogens produce alterations of perceptions , mood , and cognition , and have anxiolytic , antidepressant , and antiaddictive properties .
These drugs act as agonists of frontocortical 5-HT2A receptors , but the neural basis of their effects are not well understood .
Thus , we conducted a systematic review of neuroimaging studies analyzing the effects of serotonergic hallucinogens in man .
Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin
Psychedelic drugs have a long history of use in healing ceremonies , but despite renewed interest in their therapeutic potential , we continue to know very little about how they work in the brain . Here we used psilocybin , a classic psychedelic found in magic mushrooms , and a task-free functional MRI ( fMRI ) protocol design ed to capture the transition from normal waking consciousness to the psychedelic state . Arterial spin labeling perfusion and blood-oxygen level-dependent ( BOLD ) fMRI were used to map cerebral blood flow and changes in venous oxygenation before and after intravenous infusions of placebo and psilocybin .  Fifteen healthy volunteers were scanned with arterial spin labeling and a separate 15 with BOLD . As predicted , profound changes in consciousness were observed after psilocybin , but surprisingly , only decreases in cerebral blood flow and BOLD signal were seen , and these were maximal in hub regions , such as the thalamus and anterior and posterior cingulate cortex ( ACC and PCC ) . Decreased activity in the ACC/medial prefrontal cortex ( mPFC ) was a consistent finding and the magnitude of this decrease predicted the intensity of the subjective effects . Based on these results , a seed-based pharmaco-physiological interaction/functional connectivity analysis was performed using a medial prefrontal seed . 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
Long-term use was associated with thinning of the posterior cingulate cortex , thickening of the anterior cingulate cortex , and decreased neocortical 5-HT2A receptor binding .
Despite the high method ological heterogeneity and the small sample sizes , the results suggest that hallucinogens increase introspection and positive mood by modulating brain activity in the fronto-temporo-parieto-occipital cortex
Serotonergic hallucinogens produce alterations of perceptions , mood , and cognition , and have anxiolytic , antidepressant , and antiaddictive properties .
These drugs act as agonists of frontocortical 5-HT2A receptors , but the neural basis of their effects are not well understood .
Thus , we conducted a systematic review of neuroimaging studies analyzing the effects of serotonergic hallucinogens in man .