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Enhanced visual contrast suppression during peak psilocybin effects: Psychophysical results from a pilot randomized controlled trial

Summary

Researchers studied how psilocybin affects the way our visual system processes contrast and surrounding visual information. Participants completed vision tests after taking psilocybin or placebo, and the results showed that psilocybin made people more influenced by surrounding visual elements when judging the brightness of objects. Interestingly, the stronger the visual effects people experienced from psilocybin, the more their perception was influenced by these surroundings. This finding might help explain how psilocybin affects mood and could help scientists better understand depression and other conditions affecting vision.

Background

Surround suppression is a visual perception effect wherein the apparent contrast of a center stimulus is reduced when surrounded by higher-contrast stimuli. The neuromodulatory processes underlying surround suppression remain unclear. Psilocybin is a serotonergic psychedelic known for robust effects on visual perception.

Objective

To examine whether surround suppression is altered under peak effects of psilocybin using a contrast-matching task with different center-surround stimulus configurations in healthy human participants compared with placebo control.

Results

Psilocybin significantly enhanced surround suppression compared to placebo, with lower PSE values in orthogonal and parallel surround conditions but not in the no-surround condition. Intensity of subjective psychedelic visuals correlated positively with magnitude of surround suppression. Catch trial accuracy remained high under psilocybin, indicating task performance was maintained.

Conclusion

Preliminary findings suggest psilocybin enhances visual surround suppression during peak drug effects, particularly affecting contextual visual processing. These findings may have implications for understanding visual disruption in mental health disorders and challenge assumptions comparing psilocybin effects to psychosis.
  • Published in:Journal of Vision,
  • Study Type:Clinical Trial,
  • Source: PMID: 39499526, DOI: 10.1167/jov.24.12.5
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