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

Psychedelics are experiencing a resurgence in scientific and clinical interest, but no universal agreement exists on the mechanisms behind their effects on subjective experience, brain dynamics, or therapeutic benefits. The effects of psychedelics on low-level sensory—particularly visual—dimensions and corresponding brain dynamics have often been dismissed as epiphenomenal byproducts. Reviewing evidence from neuroimaging, pharmacology, questionnaires, and clinical studies, the authors propose that psychedelic-induced alterations in low-level sensory dimensions are not entirely reducible to high-level alterations but co-occur in a dialogical interplay. These sensory changes likely play a causally relevant role in determining high-level alterations and therapeutic outcomes, suggesting that reevaluating sensory dimensions in psychedelic states is valuable for neuroscience and clinical practice.

Study at a glance

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-induced 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.