New genetic clues that could help explain the biology of synaesthesia are reported by scientists from the Max Planck Institute for Psycholinguistics and the University of Cambridge. The researchers carefully analysed the DNA of three families in which multiple members, across several different generations, experience colour when listening to sounds.
One in 25 people have synesthesia, in which an experience involving one sense is associated with perception in another sense — for example, seeing colors when listening to music.
Some people with synaesthesia may see sounds, while others may taste them or feel them as shapes. This kind of sensory cross-talk comes in many forms, and develops during early childhood. It has been known for over a century that synaesthesia runs in families, giving a strong hint that inherited factors are important.
Dr. Amanda Tilot, a geneticist at the Max Planck Institute for Psycholinguistics, said;
“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. We suspect some of the answers lie in people’s genetic makeup.”
The team took advantage of advances in genome sequencing, enabling them to identify genetic variants in the synaesthesia families and track how they were passed on from one generation to the next.
In particular, they focused attention on rare DNA changes that altered the way genes code for proteins, and that perfectly matched the inheritance of synaesthesia in each of the three families.
While the highlighted DNA variants differed between the three families, a common theme emerged to connect them: an enrichment for genes involved in axonogenesis and cell migration. Axonogenesis, the formation of new axons, is a key process enabling brain cells to wire up to their correct partners.
Professor Simon Fisher, Director of the Max Planck Institute, who led the research, said,
“We knew from earlier studies by the Cambridge team that no single gene can account for this intriguing trait; even families who experience the same form of synaesthesia are likely to differ in terms of specific genetic explanations. Our hope was that the DNA data might point to shared biological processes as candidates for involvement in synaesthesia.”
Professor Simon Baron-Cohen, Director of the Autism Research Centre, Cambridge University, commented,
“This research is revealing how genetic variation can modify our sensory experiences, potentially via altered connectivity in the brain. Synaesthesia is a clear example of neurodiversity which we should respect and celebrate.”
To better understand these findings, the team is looking for new families and individuals to join their study. To learn more about their research and take a short test to find out if you experience a common form of synaesthesia, go to http://www.mpi.nl/synaesthesia.
Support for the work was provided by the European Commission, the Hertie Foundation through the Eric Kandel Young Neuroscientists Prize and by the Max Planck Society.
Amanda K. Tilot, Katerina S. Kucera, Arianna Vino, Julian E. Asher, Simon Baron-Cohen, Simon E. Fisher
Rare variants in axonogenesis genes connect three families with sound–color synesthesia
Proceedings of the National Academy of Sciences Mar 2018, 201715492; DOI: 10.1073/pnas.1715492115
Top Image: Dominik from Germany CC BY-SA 2.0, via Wikimedia Commons