Synesthetic hallucinations induced by psychedelic drugs in a congenitally blind man.

A case report describes the experience of a congenitally blind individual, BP, after using LSD. BP reported no visual hallucinations, but instead experienced novel sensory alterations in other functioning senses, consistent with synthetic synesthesia and crossmodal correspondences. The absence of visual hallucinations and the low rates of psychosis observed in the congenitally blind population suggest that acquired visual experiences may be necessary for visual-like hallucinations, and that psychedelic-induced synesthesia can manifest through non-visual modalities.

Study at a glance

Abstract

This case report offers rare insights into crossmodal responses to psychedelic drug use in a congenitally blind (CB) individual as a form of synthetic synesthesia. BP's personal experience provides us with a unique report on the psychological and sensory alterations induced by hallucinogenic drugs, including an account of the absence of visual hallucinations, and a compelling look at the relationship between LSD induced synesthesia and crossmodal correspondences. The hallucinatory experiences reported by BP are of particular interest in light of the observation that rates of psychosis within the CB population are extremely low. The phenomenology of the induced hallucinations suggests that experiences acquired through other means, might not give rise to "visual" experiences in the phenomenological sense, but instead gives rise to novel experiences in the other functioning senses.