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 .
Topographic pharmaco-EEG mapping of the effects of the South American psychoactive beverage ayahuasca in healthy volunteers.
AIMS Ayahuasca is a traditional South American psychoactive beverage used in Amazonian shamanism , and in the religious ceremonies of Brazilian-based syncretic religious groups with followers in the US and several European countries . This tea contains measurable amounts of the psychotropic indole N , N-dimethyltryptamine ( DMT ) , and beta-carboline alkaloids with MAO-inhibiting properties . In a previous report we described a profile of stimulant and psychedelic effects for ayahuasca as measured by subjective report self- assessment instruments . In the present study the cerebral bioavailability and time-course of effects of ayahuasca were assessed in humans by means of topographic quantitative-electroencephalography ( q-EEG ) , a noninvasive method measuring drug-induced variations in brain electrical activity . METHODS Two doses ( one low and one high ) of encapsulated freeze-dried ayahuasca , equivalent to 0.6 and 0.85 mg DMT kg(-1 ) body weight , were administered to 18 healthy volunteers with previous experience in psychedelic drug use in a double-blind crossover placebo-controlled clinical trial . Nineteen-lead recordings were undertaken from baseline to 8 h after administration . Subjective effects were measured by means of the Hallucinogen Rating Scale ( HRS ) . RESULTS Ayahuasca induced a pattern of psychoactive effects which result ed in significant dose-dependent increases in all subscales of the HRS , and in significant and dose-dependent modifications of brain electrical activity . Absolute power decreased in all frequency b and s , most prominently in the theta b and . Mean absolute power decreases ( 95 % CI ) at a representative lead ( P3 ) 90 min after the high dose were -20.20+/-15.23 microV2 and -2.70+/-2.21 microV2 for total power and theta power , respectively . Relative power decreased in the delta ( -1.20+/-1.31 % after 120 min at P3 ) and theta ( -3.30+/-2.59 % after 120 min at P3 ) b and s , and increased in the beta b and , most prominently in the faster beta-3 ( 1.00+/-0.88 % after 90 min at P3 ) and beta-4 ( 0.30+/-0.24 % after 90 min at P3 ) subb and s. Finally , an increase was also seen for the centroid of the total activity and its deviation . EEG modifications began as early as 15 - 30 min , reached a peak between 45 and 120 min and decreased thereafter to return to baseline levels at 4 - 6 h after administration . CONCLUSIONS The central effects of ayahuasca could be objective ly measured by means of q-EEG , showing a time pattern which closely paralleled that of previously reported subjective effects . The modifications seen for the individual  q-EEG  variables were in line with those previously described for other serotonergic psychedelics and share some features with the profile of effects shown by pro-serotonergic and pro-dopaminergic drugs . The q-EEG profile supports the role of 5-HT2 and dopamine D2-receptor agonism in mediating the effects of ayahuasca on the central nervous system
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 .