Neuroimaging & Brain Measures

More than meets the eye: The role of sensory dimensions in psychedelic brain dynamics, experience, and therapeutics

This pre-print (2022) reviews the current body of evidence surrounding the effects psychedelics have on low-level sensory dimensions of experience, and corresponding brain dynamics, particularly visual dimensions. It is proposed that psychedelic-induced alterations in low-level sensory dimensions of experience are not entirely causally reducible to alterations in high-level dimensions, but rather co-occur in a dialogical interplay and play a causally relevant role in determining high-level alterations and therapeutic outcomes.

Authors

  • Leor Roseman

Published

Neuropharmacology
meta Study

Abstract

Psychedelics are undergoing a major resurgence of scientific and clinical interest. While multiple theories and frameworks have been proposed, there is yet no universal agreement on the mechanisms underlying the complex effects of psychedelics on subjective experience and brain dynamics, nor their therapeutic benefits. Despite being prominent in psychedelic phenomenology and distinct from those elicited by other classes of hallucinogens, the effects of psychedelics on low-level sensory - particularly visual - dimensions of experience, and corresponding brain dynamics, have often been disregarded by contemporary research as ‘epiphenomenal byproducts’. Here, we review available evidence from neuroimaging, pharmacology, questionnaires, and clinical studies; we propose extensions to existing models, provide testable hypotheses for the potential therapeutic roles of psychedelic-induced visual hallucinations, and simulations of visual phenomena relying on low-level cortical dynamics. In sum, we show that psychedelic-inducead alterations in low-level sensory dimensions 1) are unlikely to be entirely causally reconducible to high-level alterations, but rather co-occur with them in a dialogical interplay, and 2) are likely to play a causally relevant role in determining high-level alterations and therapeutic outcomes. We conclude that reevaluating the currently underappreciated role of sensory dimensions in psychedelic states will be highly valuable for neuroscience and clinical practice, and that integrating low-level and domain-specific aspects of psychedelic effects into existing nonspecific models is a necessary step to further understand how these substances effect both acute and long-term change in the human brain.

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Research Summary of 'More than meets the eye: The role of sensory dimensions in psychedelic brain dynamics, experience, and therapeutics'

Introduction

Psychedelics such as psilocybin, DMT, LSD and mescaline produce a wide range of effects across the brain functional hierarchy, from low-level sensory alterations to changes in mood and high-level cognition. Contemporary explanatory frameworks commonly emphasise a reduction in top-down control and increased bottom-up influence of sensory information, and many models centre on the role of 5-HT2A receptor activation. Nevertheless, current dominant accounts—exemplified by the REBUS model and by thalamic-gating proposals—tend to treat psychedelic sensory effects, especially visual phenomena, as nonspecific or epiphenomenal, and therefore underplay modality-specific cortical dynamics and their potential causal role in higher-level changes and therapeutic outcomes. Aqil and colleagues set out to reassess the role of low-level sensory dimensions—particularly vision—in psychedelic brain dynamics, subjective experience, and therapeutics. The paper reviews evidence from neuroimaging, pharmacology, questionnaires and clinical studies, presents computational considerations and simulations relevant to visual phenomena, and proposes testable hypotheses about how sensory alterations might causally interact with high-level processes and contribute to therapeutic effects. The authors argue for integrating domain-specific, low-level mechanisms into existing nonspecific models to better understand both acute psychedelic phenomenology and longer-term clinical outcomes.

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Study Details

  • Study Type
    meta
  • Journal
  • Topic
  • Author
  • APA Citation

    Aqil, M., & Roseman, L. (2023). More than meets the eye: The role of sensory dimensions in psychedelic brain dynamics, experience, and therapeutics. Neuropharmacology, 223, 109300. https://doi.org/10.1016/j.neuropharm.2022.109300

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