title: Modulating the rate and rhythmicity of perceptual rivalry alternations with the mixed 5-HT2A and 5-HT1A agonist psilocybin.
abstract: Binocular rivalry occurs when different images are presented simultaneously to corresponding points within the left and right eyes. Under these conditions, the observer's perception will alternate between the two perceptual alternatives. Motivated by the reported link between the rate of perceptual alternations, symptoms of psychosis and an incidental observation that the rhythmicity of perceptual alternations during binocular rivalry was greatly increased 10 h after the consumption of LSD, this study aimed to investigate the pharmacology underlying binocular rivalry and to explore the connection between the timing of perceptual switching and psychosis. Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine, PY) was chosen for the study because, like LSD, it is known to act as an agonist at serotonin (5-HT)1A and 5-HT2A receptors and to produce an altered state sometimes marked by psychosis-like symptoms. A total of 12 healthy human volunteers were tested under placebo, low-dose (115 microg/kg) and high-dose (250 microg/kg) PY conditions. In line with predictions, under both low- and high-dose conditions, the results show that at 90 min postadministration (the peak of drug action), rate and rhythmicity of perceptual alternations were significantly reduced from placebo levels. Following the 90 min testing period, the perceptual switch rate successively increased, with some individuals showing increases well beyond pretest levels at the final testing, 360 min postadministration. However, as some subjects had still not returned to pretest levels by this time, the mean phase duration at 360 min was not found to differ significantly from placebo. Reflecting the drug-induced changes in rivalry phase durations, subjects showed clear changes in psychological state as indexed by the 5D-ASC (altered states of consciousness) rating scales. This study suggests the involvement of serotonergic pathways in binocular rivalry and supports the previously proposed role of a brainstem oscillator in perceptual rivalry alternations and symptoms of psychosis.
authors.affiliation: Vision Touch and Hearing Research Center, School of Biomedical Science, University of Queensland, Australia. o.carter@uq.edu.au
authors.forename: Olivia L
authors.initials: OL
authors.lastname: Carter
authors.forename: John D
authors.initials: JD
authors.lastname: Pettigrew
authors.forename: Felix
authors.initials: F
authors.lastname: Hasler
authors.forename: Guy M
authors.initials: GM
authors.lastname: Wallis
authors.forename: Guang B
authors.initials: GB
authors.lastname: Liu
authors.forename: Daniel
authors.initials: D
authors.lastname: Hell
authors.forename: Franz X
authors.initials: FX
authors.lastname: Vollenweider
mesh_terms: D000328:Adult; D000339:Affect / Q000187:drug effects; D001933:Brain Stem / Q000502:physiology; D003243:Consciousness / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006213:Hallucinogens / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects; D010465:Perception / Q000187:drug effects*; D011562:Psilocybin / Q000494:pharmacology*; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D058825:Serotonin 5-HT1 Receptor Agonists; D058826:Serotonin 5-HT2 Receptor Agonists; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D015348:Vision, Binocular / Q000502:physiology; D014796:Visual Perception / Q000187:drug effects
chemical_list: D006213:Hallucinogens; D058825:Serotonin 5-HT1 Receptor Agonists; D058826:Serotonin 5-HT2 Receptor Agonists; D017366:Serotonin Receptor Agonists; D011562:Psilocybin; D012701:Serotonin