This emotion-processing structure is particularly prone to serotonergic modulation. Psilocybin, reduces the processing of negative stimuli ( Preller et al., 2017) which is relevant concerning affective processing in the amygdala. This substance is a preferential serotonin (5-HT) 2A/1A receptor agonist ( Halberstadt and Geyer, 2011). The psychedelic experience produced by psilocybin (Psi) (a substance found in “magic mushrooms”) is characterized by “unconstrained” cognition and profound alterations in the perception of time, space and selfhood ( Mason et al., 2021). Moreover, 5-HT2AR activation through LSD has been implicated in the formation of visual hallucinations and cognitive impairments ( Schmidt et al., 2018).
![hallucination drugs hallucination drugs](https://i.ebayimg.com/images/g/p5MAAOSwurlfKpUD/s-l640.jpg)
In particular, neuroimaging studies have investigated the neural correlates of alertness based on agonistic modulation of the human serotonin 2A receptor (5-HT2AR, 5-hydroxytryptamine2A) (using dimethyltryptamine-DMT) and N-methyl-D-aspartic acid (NMDA) antagonism (using ketamine) for psychosis ( Daumann et al., 2010). The approach of experimentally inducing states of psychosis was proven to be very useful to understand the effects of distinct substances in the brain in the so–called pharmacological fMRI approach ( Daumann et al., 2010). The neural correlates of visual and auditory alertness in these conditions have been a matter of study. Sensory hallucinations and attentional deficits are common manifestations in schizophrenia and other neuropsychiatric disorders. The relation between psychedelic experience and psychosis remains intriguing ( Cumming et al., 2021). The current work summarizes the level of (in) consistency between functional imaging outcomes from connectivity and activation studies that might help to further clarify the implication of previous reports and their importance concerning the therapeutic potential of these drugs. Here we aimed to perform a quantitative meta-analysis of neuroimaging studies in this field. A current research trend involves testing the effects of hallucinogens as potential therapeutic alternatives for psychiatric disorders ( Kraehenmann, 2017 Lowe et al., 2021). In recent years, many studies have used substances to study the neuronal correlates of altered states of consciousness ( dos Santos et al., 2016). Pharmacologic challenges with tryptamine hallucinogen substances have been used as models for psychosis. In sum, the available evidence points towards strong neuromodulatory effects of tryptamine psychedelics in key brain regions involved in mental imagery, theory of mind and affective regulation, pointing to potential therapeutic applications of this class of substances. Finally, we found a robust neuromodulatory effect in the right amygdala. Moreover, many of the above-mentioned regions also have a significant density of both 5HT1A/5HT2A receptors, and available PET studies on the effects of psychedelics on receptor occupancy are still quite scarce, precluding a metanalytic approach. However, we also found relevant patterns in other brain regions such as dorsolateral prefrontal cortex. We did indeed find that regions with changed connectivity and/or activation patterns match regions with high density of 5HT2A receptors, namely visual BA19, visual fusiform regions in BA37, dorsal anterior and posterior cingulate cortex, medial prefrontal cortex, and regions involved in theory of mind such as the surpramarginal gyrus, and temporal cortex (rich in 5HT1A receptors).
![hallucination drugs hallucination drugs](https://positivechoices.org.au/img/library/hallucinogens-002.png)
We investigated the question whether the changes in activation patterns and connectivity map into regions with larger 5HT1A/5HT2A receptor binding, as expected from indolaemine hallucinogens (in spite of the often reported emphasis only on 5HT2AR). We performed a quantitative meta-analysis of brain imaging studies to investigate the effects of substances within this class (e.g., LSD, Psilocybin, DMT, Ayahuasca) in the brain from a molecular and functional point of view. It is widely believed that they act mainly through 5HT2A receptors but their effects on neural activation of distinct brain systems are not fully understood. There is an increasing interest in the neural effects of psychoactive drugs, in particular tryptamine psychedelics, which has been incremented by the proposal that they have potential therapeutic benefits, based on their molecular mimicry of serotonin.
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