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 .
Pharmacological modulation of the neural basis underlying inhibition of return (IOR) in the human 5-HT2A agonist and NMDA antagonist model of psychosis
Rationale Attentional deficits are common symptoms in schizophrenia . Recent evidence suggests that schizophrenic patients show abnormalities in spatial orienting of attention , particularly a deficit of inhibition of return ( IOR ) . IOR is mostly thought to reflect an automatic , inhibitory mechanism protecting the organism from redirecting attention to previously scanned , insignificant locations . Pharmacologic challenges with hallucinogens have been used as models for psychosis . Objectives The aim of this study was to investigate the neural correlates underlying orienting of attention in the human N-methyl-d-aspartic acid antagonist and 5-HT2A agonist models of psychosis . Material s and methods Fourteen healthy volunteers participated in a r and omized , double-blind , cross-over event-related functional magnetic resonance imaging ( fMRI ) study with dimethyltryptamine ( DMT ) and S-ketamine . We administered a covert orienting of attention task with nonpredictive peripheral cues , and we scanned the subjects on two separate days at least 14 days apart with a placebo and a verum condition on each day . Results DMT , but not S-ketamine , slowed down reaction times significantly . IOR was blunted after DMT , but not after S-ketamine . Relative to placebo , S-ketamine increased activation in the IOR condition in the right superior frontal gyrus , left superior temporal gyrus , and right midfrontal frontal gyrus . Conclusions The discrepancy between the behavioral and functional imaging outcome indicates that pharmacological fMRI might be a sensitive tool to detect drug-modulated blood oxygenation level-dependent signal changes in the absence of behavioral abnormalities . Our findings might help to further clarify the contradictory findings of IOR in schizophrenic patients and might , thus , shed more light on possible differential pathomechanisms of schizophrenic symptoms
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 .