Synesthesia :: Biology Essays Research Papers

Synesthesia When I was very young, I experienced a recurring dream that I was staring, entranced, at a delicate white flower. It was like nothing I had seen or experienced in my waking life, because the pristine, thinly-veined petals were such an exquisite color that it manifested itself upon my dreaming brain as a color and a sound. The white song was a single note - like a distant choir lifting its voice in concerted wonder. I would wake from the dreams bewildered at the ease with which my brain, when asleep, could produce in me a tangle of sensations I could never enjoy while conscious. The neurological phenomenon of cross-modal, or inter-sensory, perception stemming from a single stimulus is called "synesthesia." The word comes from the Greek syn-, meaning "union," and -aisthesis, meaning "sensation" (2). Although my childhood dreams had some synesthetic character, I have never had a comparable conscious experience. "Synesthesia proper," or neurologically-based synesthesia, is defined as the regular, involuntary experience of external, durable, and generic perceptions in senses not commonly associated with a certain stimulus (1,2) . Although there are numerous possible combinations of synesthetic events, not every permutation is observed. The estimated number of affected individuals ranges from one in five hundred, who perceive colored letters or musical notes, to one in three thousand, who experience colored sounds or colored tastes (2). It is estimated that one in fifteen thousand individuals experiences taste-touch overlap and other, rarer forms of the condition (2). Another, more conservative, estimate suggests that only one in twenty-five thousand individuals is a synesthete (3). While certain synesthetic events are triggered by a sensory appeal to the imagination, i.e. as an artifice of literature or art, true synesthetes report only very rudimentary secondary sensory perceptions for a given input (1). That is, while many of us associate the smell of cut grass with the color green within our internal perception, a synesthete with a smell-sight perception overlap might perceive colored shapes or textures within the external environment upon smelling the grass. Synesthesia is an additive sensory condition. Rather than replace one perception with another, a single sensory input stimulates simultaneous responses in two or more of the senses (2). It is most frequently experienced as a unidirectional condition; while one stimulus, such as sound, induces sensation within another sensory realm, such as sight, the converse does not usually occur (2).