Synaesthesia is the curious non-pathological phenomenon, thought to occur in 5-10% of people, where stimulation of one sensory or cognitive pathway leads to involuntary stimulation of another (or multiple) sensory or cognitive pathway(s).
Some people with synaesthesia perceive letters or numbers as inherently coloured; others feel that numbers, months of the year, or days of the week have a specific location in space, and so on.
The phenomenon is more prevalent in people with autism spectrum disorder and savant abilities. A list of confirmed and proposed “synaesthetes” (both living and dead) can be found here.
While the underlying biological mechanisms of synaesthesia haven’t yet been discovered, it has been known for over a century that sensory cross-talk tends to run in families.
“Brain imaging of adults with synaesthesia suggests that their circuits are wired a little differently compared to people who don’t make these extra sensory associations. What we don’t know yet is how these differences develop,” said Dr Amanda Tilot, a geneticist at the Max Planck Institute for Psycholinguistics (MPP).
By leveraging advances in the field of genomic sequencing, a group of researchers from MPP and the University of Cambridge had succeeded in gleaning a number of new genetic clues that could bring the development of a full biological picture that much closer.
In the study, the researchers carefully analysed the DNA of three unrelated families in which at least five members, across three or more generations, had reported experiencing colour in parallel with sound.
By focusing on rare DNA changes that alter the way genes code for proteins, the group had identified a common theme running across the different variants of DNA: an enrichment for genes involved in axonogenesis (a key process for neuronal connections within and across brain regions) and cell migration.
“Over 130 years after the first reports of familiar synaesthesia, these results provide a molecular starting point for studies addressing the origins of healthy variation in sensory integration”, wrote the authors in their paper, published in the journal PNAS.
Since the study is currently ongoing, the research team is looking for volunteers. If you’re interested in taking a synaesthesia test, and/or taking part in the study, go to https://www.mpi.nl/synaesthesia.