Serotonergic psychedelics temporarily modify information transfer in humans
This study (n=10) investigated the brain's directed functional connectivity (FC) under the influence of ayahuasca, and found that neural hierarchies were temporarily disrupted with decreased top-down control and increased bottom-up information transfer.
Authors
- Jordi Riba
- Joan Francesc Alonso
Published
Abstract
Background
Psychedelics induce intense modifications in the sensorium, the sense of “self,” and the experience of reality. Despite advances in our understanding of the molecular and cellular level mechanisms of these drugs, knowledge of their actions on global brain dynamics is still incomplete. Recent imaging studies have found changes in functional coupling between frontal and parietal brain structures, suggesting a modification in information flow between brain regions during acute effects.
Methods
Here we assessed the psychedelic-induced changes in directionality of information flow during the acute effects of a psychedelic in humans. We measured modifications in connectivity of brain oscillations using transfer entropy, a nonlinear measure of directed functional connectivity based on information theory. Ten healthy male volunteers with prior experience with psychedelics participated in 2 experimental sessions. They received a placebo or a dose of ayahuasca, a psychedelic preparation containing the serotonergic 5-HT2A agonist N,N-dimethyltryptamine.
Results
The analysis showed significant changes in the coupling of brain oscillations between anterior and posterior recording sites. Transfer entropy analysis showed that frontal sources decreased their influence over central, parietal, and occipital sites. Conversely, sources in posterior locations increased their influence over signals measured at anterior locations. Exploratory correlations found that anterior-to-posterior transfer entropy decreases were correlated with the intensity of subjective effects, while the imbalance between anterior-to-posterior and posterior-to-anterior transfer entropy correlated with the degree of incapacitation experienced.
Conclusions
These results suggest that psychedelics induce a temporary disruption of neural hierarchies by reducing top-down control and increasing bottom-up information transfer in the human brain.
Research Summary of 'Serotonergic psychedelics temporarily modify information transfer in humans'
Introduction
Psychedelic drugs produce profound alterations in perception, selfhood and the experience of reality, and renewed interest in their therapeutic and mechanistic potential has stimulated research into their neural actions. Earlier neuroimaging and electrophysiological work has implicated medial frontal regions (including the anterior cingulate cortex) and parietal/posterior midline regions (including the posterior cingulate and dorsolateral parietal cortex) in the acute effects of serotonergic psychedelics. Radiotracer studies typically report increased frontal metabolism or perfusion after drugs such as mescaline, psilocybin and ayahuasca, while EEG and MEG studies have shown reductions in oscillatory power—often most prominent in parieto-occipital regions. Recent resting-state MRI work has additionally suggested altered coupling between frontal and parietal midline structures, but the directionality of information transfer between anterior and posterior areas during the psychedelic state has remained unclear. Alonso and colleagues set out to test whether psychedelics modify the directionality of information flow across the human brain. Specifically, the investigators assessed directed functional connectivity of EEG oscillations using transfer entropy (TE), a nonlinear informationtheory measure that can indicate causal, directional dependencies between signals. The study tested the hypothesis that a serotonergic psychedelic would perturb neural hierarchies and alter top-down versus bottom-up information transfer between frontal and posterior regions during the acute drug effects.
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Study Details
- Study Typeindividual
- Journal
- Compounds
- Topic
- Authors
- APA Citation
Alonso, J. F., Romero, S., Mañanas, M. À., & Riba, J. (2015). Serotonergic psychedelics temporarily modify information transfer in humans. International Journal of Neuropsychopharmacology, 18(8). https://doi.org/10.1093/ijnp/pyv039
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