What does green taste like? What colour is the note B#? Synesthesia is a rare neurological condition affecting less than one percent of the population; in which the stimulation of one sensory pathway produces an experience in another. For example, hearing a certain sound might trigger someone with synesthesia to see the colour yellow. It can also produce a result within a different facet of the same sensory pathway (eg: The letter N might always be seen as light warm brown).
For long this conditioned was often dismissed and attributed to an over active imagination, however now it is known to have a biological basis.
A recent study published on the 15th of February in the American Journal of Human Genetics made major developments towards finding the genes underlying synaesthesia; with this research even carrying possible implications towards an improved understanding of cognitive development.
The study's author, Dr. Julian E. Asher claims that the "genetics of synaesthesia are not well understood". The research, conducted as part of Dr. Asher's PHD involved a genome-wide screen, searching for susceptibility genes linked to auditary-visual synaesthesia. Four regions linked to susceptibility to synaesthesia were found, however a previous theory related to the X-chromosome could not be supported. This suggests that the origins are more complex than first thought and the genetic basis may in fact be may be a result of multiple genes subject to multiple modes of inheritance. Although it is difficult to identify specific candidate genes due to the resolution of the scan, a number of interesting observations were made.
The region on chromosome two with the strongest connection has known links to autism and within the four candidate regions are genes associated with epilepsy, dyslexia, learning and memory. Dr Asher proclaimed that the "study comprises a significant step towards identifying the genetic substrates underlying synaesthesia, with important implications for our understanding of the role of genes in human cognition and perception".
Top Right: How a person with synaesthesia might see letters and numbers.
Above: A human chromosome.
Sources:
http://www.sciencedaily.com/releases/2009/02/090205133728.htm
http://www.sciencedaily.com/videos/2007/0107-what_color_is_a.htm
Images:
http://secretartgallery.com/articles/synesthesia/
http://sfari.org/uploads/2f3a26fc-a705-e0a4-85c5-2712b4bfacfd_400.jpg
