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What Causes Cross Modality in Synesthesia?

Most people see colors and hear sounds and music. People with the condition synesthesia, however, experience a cross-wiring of their sense perceptions that may lead them to hear music in color or see the sound music produces. Synesthesia is a a rare and complex neurologic condition.

  1. Cross-Modality

    • Modality is a term that medical science uses for the senses. Modalities are hearing, seeing, tasting or touching. Cross-modality is a term used by medical science to describe how the senses of a person with synesthesia become mismatched from the way you normally perceive them. Instead of hearing a sound, a person with color-auditory synesthesia will see a sound as a particular color. Various combinations of cross-modalities describe the sensory perception of the synesthetic person.

    Idiopathic Synesthesia

    • People who have had the cross-modal experience for as long as they can remember are called idiopathic synesthetics. Different theories explain what the natural causes are for people who have this developmental form of synethesia. One theory suggests that cross-modality is the result of genetics. Another theory suggests that cross-modality is a natural mental state in the development of a developing baby's brain and that some people do not grow out of it like most other people do. One theory suggests that everyone is a cross-modal synesthetic but unaware of it.

    Nonidiopathic Synesthesia

    • The mixed-sensory state can be induced by external factors and leave a person with synesthesia. One cause for externally induced cross-modality are the effects of a high fever for a sustained amount of time. Another instance of nonidiopathic synesthesia can result from brain damage, either from a traumatic brain injury or from a stroke. Drug-induced synesthesia is rare, but hallucinogenic substances have also been known to produce synesthesia in people.

    Mechanism of Expression

    • One theory is that neuropathways in your brain that link the lymbic system, which is responsible for emotions, to the neocortex, the part of the brain responsible for higher-order thinking, are either severed or cross-wired. Brain scans show that parts of the brain associated with the different senses do light up for synesthetics differently than they do for people with standard sense perceptions.

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