Synaesthesia is a genetic condition caused by the crossing of sensory nerves, although it can be influenced by the environment, and presents in a number of forms. Generally, when a synaesthete experiences a certain sense, they unconsciously and uncontrollably experience other senses as well. For example some people associate words with colours (grapheme à colour synaesthesia), while some associate sounds with taste. This can cause problems if not diagnosed, especially for children, as it can cause distraction and affect learning capabilities. For example, if a child associate’s sound with colour, then a noisy classroom would overwhelm them with colours and prevent them from learning. At present there are only behavioural tests which are used to diagnose synaesthesia, which can be unreliable, as the child may not understand how to do the test. By determining which genes cause this phenomenon it can facilitate the development of a genetic test which would allow for early diagnoses and improve academic capabilities of synaesthetes.
A study performed by Julian Asher of the Imperial College in London and the Wellcome Trust Centre for Human Genetics at the University of Oxford found that certain chromosomes have strong links to synaesthesia. They tested 196 individuals from 43 families and found that 121 of these participants exhibited the trait of associating a specific colour after hearing a sound. They analysed the genome of each person by tracking “common markers”, which are “specific sets of base pairs that are repeated throughout the genome and which vary from person to person”. These markers were then compared within families and the researchers could infer which parent this is inherited from. Finally, by looking at which participants exhibited symptoms, the regions associated with synaesthesia could be identified.
There were regions on four chromosomes that strongly exhibited links to synaesthesia. Chromosome 2, which is associated with autism and epilepsy, showed the strongest link. Some autistic savants (people who suffer developmental disorders but show extraordinary proficiency in select areas), have shown to have a combination of both autism and synaesthesia. The researchers believe this may indicate that they are all subtly linked on a genetic or neurological level. Chromosomes 5, 6 and 12 also seem to be linked and are associated with brain structure and functions.
With further study, they are hoping to determine the specific gene sequence and formulate a diagnostic test for this condition. For more information visit the New Scientist link below.
References
About Synesthesia. (2009, April 23). Retrieved 27th April, 2009, from The Australian Synesthesia website: http://www.synesthesia.com.au/id1.html
Genetic Roots of Synaesthesia unearthed. (2009, February 5). Retrieved 26th April, 2009, from the New Scientist website: http://www.newscientist.com/article/dn16537-genetic-roots-of-synaesthesia-unearthed.html
By Kelly Baker
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