This reanalysis (n=24) of an RCT with psilocybin (up to 22mg/70kg) finds that self-inhibition of visual areas of the brain (EVA, FG) leads to complex imagery, as seen by participants. The results align with the REBUS model and highlight (again) how the bottoms-up processes of the brain are amplified under the influence of psychedelics.
Abstract of Neural mechanisms of psychedelic visual imagery
“Visual alterations under classic psychedelics can include rich phenomenological accounts of eyes-closed imagery. Preclinical evidence suggests agonism of the 5-HT2A receptor may reduce synaptic gain to produce psychedelic-induced imagery. However, this has not been investigated in humans. To infer the directed connectivity changes to visual connectivity underlying psychedelic visual imagery in healthy adults, a double-blind, randomised, placebo-controlled, cross-over study was performed, and dynamic causal modelling was applied to the resting state eyes-closed functional MRI scans of 24 subjects after administration of 0.2 mg/kg of the serotonergic psychedelic drug, psilocybin (magic mushrooms), or placebo. The effective connectivity model included the early visual area, fusiform gyrus, intraparietal sulcus, and inferior frontal gyrus. We observed a pattern of increased self-inhibition of both early visual and higher visual-association regions under psilocybin that was consistent with preclinical findings. We also observed a pattern of reduced inhibition from visual-association regions to earlier visual areas that indicated top-down connectivity is enhanced during visual imagery. The results were analysed with behavioural measures taken immediately after the scans, suggesting psilocybin-induced decreased sensitivity to neural inputs is associated with the perception of eyes-closed visual imagery. The findings inform our basic and clinical understanding of visual perception. They reveal neural mechanisms that, by affecting balance, may increase the impact of top-down feedback connectivity on perception, which could contribute to the visual imagery seen with eyes-closed during psychedelic experiences.”
Authors: Devon Stoliker, Katrin H. Preller, Leonardo Novelli, Alan Anticevic, Gary Egan, Franz X. Vollenweider & Adeel Razi
Summary of Neural mechanisms of imagery under psilocybin
Using psilocybin, a prototypical classic psychedelic derived from select species of mushrooms, this study investigates the neural mechanisms of psychedelic-induced eyes-closed visual imagery (i.e., hallucinations). This research can help us understand the relationship between neuropharmacology and large-scale neural connectivity of the visual system.
Psychedelic perceptual changes are primarily derived from agonism of the serotonergic 5-HT2A receptor (5-HT2AR). The 5-HT2AR is highly expressed in the visual and frontal areas of the brain, but the 5-HT2AR may alter neuronal activity in these areas of the brain differently.
Psychedelic-induced visual effects can occur with eyes-open or eyes-closed. Elemental imagery, complex imagery, and visual hallucinations can occur at different levels of complexity and can match the vividness and realism of eyes-open stimuli.
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Neural mechanisms of psychedelic visual imagery
https://doi.org/10.1038/s41380-024-02632-3
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Cite this paper (APA)
Stoliker, D., Preller, K. H., Novelli, L., Anticevic, A., Egan, G. F., Vollenweider, F. X., & Razi, A. (2024). Neural mechanisms of psychedelic visual imagery. Molecular Psychiatry, 1-8.
Study details
Compounds studied
Psilocybin
Topics studied
Neuroscience
Healthy Subjects
Study characteristics
Original Re-analysis
Placebo-Controlled
Double-Blind
Within-Subject
Randomized
Re-analysis
Participants
24
Humans
Institutes
Institutes associated with this publication
Monash UniversityThe Clinical Psychedelic Lab, established in 2020, within the Dept Psychiatry at Monash University is the first of its kind in Australia, leading the development and implementation of psychedelic therapies. The lab has played a central role in establishing the field of clinical psychedelic research in Australia.
Compound Details
The psychedelics given at which dose and how many times
Psilocybin 22 mg | 1xLinked Research Papers
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