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 .
Inhibition of alpha oscillations through serotonin-2A receptor activation underlies the visual effects of ayahuasca in humans
Ayahuasca is an Amazonian psychotropic plant tea typically obtained from two plants , Banisteriopsis caapi and Psychotria viridis . It contains the psychedelic 5-HT2A and sigma-1 agonist N , N-dimethyltryptamine ( DMT ) plus β-carboline alkaloids with monoamine-oxidase (MAO)-inhibiting properties . Although the psychoactive effects of ayahuasca have commonly been attributed solely to agonism at the 5-HT2A receptor , the molecular target of classical psychedelics , this has not been tested experimentally . Here we wished to study the contribution of the 5-HT2A receptor to the neurophysiological and psychological effects of ayahuasca in humans . We measured drug-induced changes in spontaneous brain oscillations and subjective effects in a double-blind r and omized placebo-controlled study involving the oral administration of ayahuasca ( 0.75 mg DMT/kg body weight ) and the 5-HT2A antagonist ketanserin ( 40 mg ) . Twelve healthy , experienced psychedelic users ( 5 females ) participated in four experimental sessions in which they received the following drug combinations : placebo+placebo , placebo+ayahuasca , ketanserin+placebo and ketanserin+ayahuasca . Ayahuasca induced EEG power decreases in the delta , theta and alpha frequency b and s. Current density in alpha-b and oscillations in parietal and occipital cortex was inversely correlated with the intensity of visual imagery induced by ayahuasca . Pretreatment  with ketanserin inhibited neurophysiological modifications , reduced the correlation between alpha and visual effects , and attenuated the intensity of the subjective experience . These findings suggest that despite the chemical complexity of ayahuasca , 5-HT2A activation plays a key role in the neurophysiological and visual effects of ayahuasca in humans
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 .