Increased frontal and paralimbic activation following ayahuasca, the pan-amazonian inebriant

A single oral dose of ayahuasca, equivalent to 1.0 mg DMT per kilogram of body weight, increased blood flow in frontal and paralimbic brain regions of fifteen male volunteers with prior psychedelic experience. Greater perfusion was observed bilaterally in the anterior insula, with stronger effects in the right hemisphere, and in the right anterior cingulate/frontomedial cortex—areas linked to somatic awareness, subjective feeling states, and emotional arousal. Additional increases occurred in the left amygdala/parahippocampal gyrus, a structure involved in emotional processing. These findings indicate that ayahuasca interacts with neural systems central to interoception and emotional processing, suggesting a modulatory role for serotonergic neurotransmission.

Study at a glance

Abstract

RationaleAyahuasca is a South American psychoactive plant tea which contains the serotonergic psychedelic N,N-dimethyltryptamine (DMT) and monoamine-oxidase inhibitors that render DMT orally active. Previous investigations with ayahuasca have highlighted a psychotropic effect profile characterized by enhanced introspective attention, with individuals reporting altered somatic perceptions and intense emotional modifications, frequently accompanied by visual imagery. Despite recent advances in the study of ayahuasca pharmacology, the neural correlates of acute ayahuasca intoxication remain largely unknown.ObjectivesTo investigate the effects of ayahuasca administration on regional cerebral blood flow.MethodsFifteen male volunteers with prior experience in the use of psychedelics received a single oral dose of encapsulated freeze-dried ayahuasca equivalent to 1.0 mg DMT/kg body weight and a placebo in a randomized double-blind clinical trial. Regional cerebral blood flow was measured 100-110 min after drug administration by means of single photon emission tomography (SPECT).ResultsAyahuasca administration led to significant activation of frontal and paralimbic brain regions. Increased blood perfusion was observed bilaterally in the anterior insula, with greater intensity in the right hemisphere, and in the anterior cingulate/frontomedial cortex of the right hemisphere, areas previously implicated in somatic awareness, subjective feeling states, and emotional arousal. Additional increases were observed in the left amygdala/parahippocampal gyrus, a structure also involved in emotional arousal.ConclusionsThe present results suggest that ayahuasca interacts with neural systems that are central to interoception and emotional processing and point to a modulatory role of serotonergic neurotransmission in these processes.