Archival ReportThe 5-HT2A/1A Agonist Psilocybin Disrupts Modal Object Completion Associated with Visual Hallucinations
Section snippets
Subjects
Healthy right-handed subjects (eight males, nine females, mean age 28.8 ± 3.5 years) were recruited through advertisement from the University of Zürich. All subjects were healthy according to physical examination including electrocardiography, and detailed blood analysis. The DIA-X diagnostic expert system (30) and a clinical interview was used to exclude subjects with present or antecedent psychiatric disorders, regular alcohol or substance abuse, and a history of major psychiatric disorders
Psychometrics
The subjective effects of psilocybin were assessed by the 5D-ASC rating scale. Repeated-measures ANOVA revealed a significant main effect of dose [F(2,32) = 36.596, p < .00001, η2 = .70], factor [F(4,64) = 12.924, p < .00001, η2 = .45], and dose × factor interaction [F(8,128) = 7.09, p < .00001, η2 = .31]. Bonferroni-corrected post hoc analysis on the VR factor, which was of primary interest in regard to the current study, indicated a significant increase between placebo and low-dose psilocybin
Discussion
This investigation revealed three main findings. First, the data indicate that the mixed 5-HT2A/1A-receptor agonist psilocybin distinctively modulates the two early visual processing components. Specifically, whereas we found a strong dose-dependent decrease of the N170 component (148- to 223-msec poststimulus), the earlier visual P1 component (90- to 144-msec poststimulus) was slightly increased over occipital electrode sites. Second, the reduction of the N170 component was stronger for the
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