Imagine closing your eyes and seeing vivid images as if your eyes were open. This fascinating phenomenon is often seen when people take hallucinogens such as psilocybin, a substance found in certain “magic” mushrooms. A new study published in the journal Neuropsychiatry found that Molecular PsychiatryScientists have used advanced imaging techniques to investigate the neural underpinnings of visual experience with eyes closed, providing new insights into visual perception and imagery.
In recent years, psilocybin has attracted attention for its potential therapeutic effects in treating psychiatric disorders such as depression, anxiety, and post-traumatic stress disorder. The compound acts primarily by activating serotonin receptors in the brain, resulting in altered perception, elevated mood, and profound changes in consciousness.
Despite psilocybin’s long history and growing interest in its therapeutic potential, the exact mechanisms by which psilocybin specifically induces visual hallucinations remain poorly understood. Hallucinations occur unpredictably in clinical disorders, limiting traditional research avenues. However, psychedelics like psilocybin reliably produce vivid visual experiences, making them valuable tools for studying the neural underpinnings of visual perception and imagery.
Previous studies have shown that psychedelics affect various brain regions involved in perception, but the detailed pathways and specific neural interactions remained unclear. Using advanced imaging techniques and a well-controlled experimental design, the authors of the new study sought to elucidate the changes in brain connectivity that underlie the unique visual experience induced by psilocybin.
“Visual effects are one of the main subjective phenomena induced by serotonergic hallucinogens, and their underlying mechanisms remain of interest in psychedelic science and other areas of research such as psychosis and dream states,” said Devon Stricker, a postdoctoral research fellow at Monash University’s Turner Institute for Brain and Mental Health and an author of the study.
“These visual phenomena complement deeper experiences related to the dissolution of self and self-related boundaries and have potential therapeutic relevance. For example, visual experiences may be perceived as personally meaningful and the dissolution of boundaries may facilitate insight or vision, which may be related to visual brain regions. Although only a subsection of these ideas are explored in this article, they offer fascinating areas for further research.”
The researchers conducted a double-blind, randomized, placebo-controlled, crossover study, considered the gold standard for minimizing bias and ensuring robust results. In this design, neither participants nor researchers knew who received psilocybin and who received a placebo in each session, and each participant experienced both conditions at different times.
The study involved 24 healthy adults aged 20-40 years with no history of psychiatric disorders. Participants underwent two sessions, at least two weeks apart. In the first session, they received psilocybin (0.2 mg per kg of body weight) and in the second, they received a placebo. In each session, resting-state functional MRI (fMRI) scans were performed 70 minutes after administration, when the effects of psilocybin were at their peak. Participants were asked to close their eyes and focus on their internal visual experience during the scan.
Under the influence of psilocybin, brain regions involved in visual processing showed increased self-inhibition, meaning these regions were less responsive to incoming sensory signals and less sensitive to external stimuli, meaning the brain’s internal activity took precedence over external sensory input.
The researchers also found enhanced connections from higher brain regions (such as the inferior frontal gyrus) to lower visual regions (such as early visual areas), suggesting that upon psilocybin ingestion, internal thought, memory, and associative processes have a greater impact on visual perception, leading to vivid and complex visual imagery.
“The brain’s response to external visual stimuli was significantly reduced, which is consistent with previous preclinical findings. This reduction in sensory input makes internally generated images more salient, supporting the hypothesis that psychedelics increase the brain’s reliance on top-down processes for visual perception.”
The vividness and complexity of visual imagery reported by participants was strongly correlated with specific brain connectivity patterns: for example, connections from the inferior frontal gyrus to the fusiform gyrus and from the fusiform gyrus to early visual areas were associated with the experience of basic and complex imagery, respectively.
“Hallucinogens appear to suppress the dominance of activity in visual regions, making these regions more susceptible to top-down influences from the brain,” Stryker told PsyPost. “This is consistent with the notion that hallucinogens are ‘mind-revealing’ substances that enhance top-down processes. This notion also resonates with past research on alpha wave suppression, suggesting that hallucinogens may suppress the mechanisms that normally prevent us from seeing visual effects when our eyes are closed.”
Despite the study’s robust design, there are some caveats to consider. The small sample size of 20 participants (after exclusions) limits the generalizability of the results. Also, the study used moderate doses of psilocybin, leaving the effects of higher doses unexplored. Additionally, the study focused on specific brain regions and the resting state, so a broader exploration of brain regions and task-based studies may provide a more comprehensive understanding.
“The science of psychedelics is still evolving, and the methodological pipeline will affect the results,” Stryker said, “so these findings should be considered preliminary. Confidence would increase if the majority of studies produced similar results.”
“Still, the findings suggest that psychedelics could be used as a tool to investigate the brain’s innate connections and their role in generating conscious experiences. Understanding how psilocybin affects brain connections could help develop new treatments for conditions involving altered perception, such as schizophrenia and certain types of hallucinations.”
“My aim is to understand changes throughout the brain that will help us understand associative and sensory processes, and how they affect top-down and bottom-up mechanisms,” Stryker explains. “Understanding these changes will shed light on how certain subjective effects are produced. This research has the potential to inform psychedelic drugs, while also shedding light on mechanisms of perception and the nature of conscious experience.”
“I have published extensive research on the neural mechanisms and psychology of psychedelic ego disruption. Pharmacology ReviewWhat might be interesting to our readers: References.”
the study, “Neural mechanisms of psychedelic visual imagery” was written by Devon Stoliker, Katrin H. Preller, Leonardo Novelli, Alan Anticevic, Gary F. Egan, Franz X. Vollenweider, and Adeel Razi.
