The effects of psilocybin on a test of after-image perception

It is demonstrated in double-blind conditions that Psilocybin significantly changes an objective measure of after-image perception and that the occurrence of these changes is highly correlated with reports of altered visual experience. A hypothesis of how this effect and the findings of others can be explained on the basis of decreased inhibitory function in visual mechanisms involved in the perception of color and detail is presented with the caution that other explanations are possible. This study, and others, indicate the importance of knowing the nature of any subjective visual disturbance at the time that objective visual functions are performed to facilitate understanding of the mechanisms involved in hallucinogenic effect.