Imagine a world where you feel sounds, taste music or see letters and numbers in colour. This may sound strange to most of us, but for synesthetes these perceptions are part of everyday life.
The word synesthesia (from the Greek words syn = together and aesthesis = perception) means “joined sensation”. It is a condition in which different senses mingle into one. One sense modality reliably causes an additional perception in a different sense or senses.
It takes different forms. Nineteen different combinations have been identified. But the combinations are almost limitless because a synesthete may have more than one form of the condition.
The most common form appears to be seeing colours in numbers and/or letters. This is called colour-language synesthesia. But other less common experiences are also possible. A synesthete may report that she feels piano music tickling her cheeks or that a person’s voice tastes like chutney.
In most cases, the sensation is triggered by external stimuli but in some cases it could be purely internal, such as associating the concept of a day or year with a sensory experience.
The sensory association is usually projected outside of the body, such as seeing the letter in colour, rather than in the mind’s eye.
Synesthesia is a highly subjective, individualised experience. Colour-language synesthetes, for example, don’t agree on which colour goes with which number or letter. However, a remarkable number agree that the letter “o” is white.
Intra-sensory associations remain constant throughout the person’s life. For example, someone who sees a number in green will always see this number in the same colour. In a study in 1993, synesthetes were 92% consistent in linking certain colours with certain sounds after a year. Non-synesthetes on the other hand were only 32% accurate after only one week.
The condition is involuntary and sensory associations cannot be suppressed. However, some people are able to ignore the associations.
This condition starts in childhood – in fact, synesthetes usually say that they have had this condition since they can remember. Synesthetes typically think that everyone else perceives the world in the same way and only find out much later that their experience is unique. Because synesthesia is so unknown and misunderstood, many people keep quiet about their condition for fear of ridicule or being misdiagnosed as psychotic.
Synesthesia is not a psychiatric disorder. Synesthetes are fully functional and psychologically stable, are usually highly intelligent and have excellent memories. The synesthetic associations help them to remember telephone numbers, appointments, names and the like. However, they may have minor difficulties with mathematics. Some also struggle with spacial navigation such as distinguishing left from right or following directions.
There is no treatment for this condition. Even if there were, most synesthetes would not want to be treated as they see their condition as a gift and an aid which optimises their functioning. In fact, many describe non-synesthetes as seeing the world in black and white.
What causes it?
The exact cause is not yet known. Synesthesia is a very difficult condition to study because research is anecdotal and has relied on self-report. What we know is that it is unlearned and involuntary. We also know that it has a genetic cause - many synesthetes have parents or siblings with the condition.
Some believe that all people are born synesthetes and have many neural connections between different areas of the brain. In non-synesthetes, many of the cross-wiring dissapear and the areas of the brain become more separated. In people with synesthesia, these connections remain for the rest of their lives.
Researchers have begun to study this phenomenon by using magnetic resonance brain imaging (MRI). It has been reported that images of the brains of colour-language synesthetes or those who report coloured hearing, show increased activation of the colour-processing areas of the cortex in response to the triggering stimulus.
A form of synesthesia can be acquired later in life. Acquired synesthesia is seen in temporal lobe epilepsy, head trauma, and mass lesions affecting the medial temporal lobe. It may also be induced temporarily by sensory deprivation, antiserotonergic hallucinogens such as LSD and peyote, or direct electrical stimulation of subcortical limbic structures.
Who has this condition?
No-one knows how prevalent this condition is. Estimates vary from between one in 2 000 and one in 25 000 people. It is more common in women than in men and left-handed people are more affected.
Famous examples of synethetes include novelist Vladimir Nabokov, composer Franz Liszt and artists David Hockney and Wassily Kandinsky. -( Ilse Pauw, updated September 2010)
Source: HealthDay News
Carte Blanche Medical interviewed people with synaesthesia. Watch the video here .
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