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 .
Psilocybin-Induced Decrease in Amygdala Reactivity Correlates with Enhanced Positive Mood in Healthy Volunteers
BACKGROUND The amygdala is a key structure in serotonergic emotion-processing circuits . In healthy volunteers , acute administration of the serotonin 1A/2A/2C receptor agonist psilocybin reduces neural responses to negative stimuli and induces mood changes toward positive states . However , it is little-known whether psilocybin reduces amygdala reactivity to negative stimuli and whether any change in amygdala reactivity is related to mood change . METHODS This study assessed the effects of acute administration of the hallucinogen psilocybin ( .16 mg/kg ) versus placebo on amygdala reactivity to negative stimuli in 25 healthy volunteers using blood oxygen level-dependent functional magnetic resonance imaging . Mood changes were assessed using the Positive and Negative Affect Schedule and the state portion of the State-Trait Anxiety Inventory . A double-blind , r and omized , cross-over design was used with volunteers counterbalanced to receive psilocybin and placebo in two separate sessions at least 14 days apart . RESULTS Amygdala reactivity to negative and neutral stimuli was lower after psilocybin administration than after placebo administration . The psilocybin-induced attenuation of right amygdala reactivity in response to negative stimuli was related to the psilocybin-induced increase in positive mood state . CONCLUSIONS These results demonstrate that acute treatment with psilocybin decreased amygdala reactivity during emotion processing and that this was associated with an increase of positive mood in healthy volunteers . These findings may be relevant to the normalization of amygdala hyperactivity and negative mood states in patients with major depression
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 .