Q. I teach an AP biology class and we were studying the effects of hallucinogens on the nervous system when one of my students brought up this question. I had briefly heard something about it years ago, but I couldn't recall the details. What is the disorder or syndrome by which the person's neurotransmitters are so cross-wired that the person can taste music, see colors of noises or other such non-related sensory perceptions to sensory stimuli?

A. I believe you are referring to a phenomenon called "synesthesia" (or synaesthesia). This is a perceptual condition in which stimulation in one sensory modality elicits a concurrent sensation in another--for example, hearing particular sounds might induce vivid experiences of color, taste or odor, as might the sight of visual symbols, such as letters or digits. (For a review of this phenomenon, see Rich & Mattingley, Nat Rev Neurosci 2002 Jan;3(1):43-52).

One recent study suggests that color-word synaesthesia may result from the activity of brain areas concerned with language and visual feature integration (Paulesu et al, Brain 1995 Jun;118 ( Pt 3):661-76). And, as you suggest, hallucinogens may provoke such effects in some individuals.

February 2003

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