By Nick Bascom
A sense-mixing condition in which people taste colors or see smells tends to run in families, and recent studies have homed in on a selection of genes that may contribute to the phenomenon, called synesthesia. Understanding the condition’s genetic basis might reveal why it has perpetuated in humans and help scientists develop cures for degenerative neurological diseases.
Only about 3 percent of the population claim to experience some form of synesthesia, but nearly half of those report having a close family member whose senses become similarly entangled. “We know that synesthesia tends to travel in families,” says experimental psychologist David Brang of the University of California, San Diego who, along with V.S. Ramachandran, discusses synesthesia genetics in an article published online November 22 in PLoS Biology.
But children often exhibit different forms of synesthesia than do their parents. This “complicates the picture and hints at the idea that more than one gene is involved,” says Brang.
A recent study led by neuroscientist David Eagleman from the Baylor College of Medicine in Houston zeroed in on a region on chromosome 16, which he and his colleagues believe holds the gene responsible for the most common form of the condition, colored sequence synesthesia (where letters and numbers are associated with a specific color). “We don’t know which gene it is yet, but we’re getting closer every day,” says Eagleman, who published his findings September 30 in Behavioural Brain Research.