New research reveals genetic mysteries behind synesthesia – a condition in which different senses seem to be crossed up in the brain, causing a person to “taste” words or even “feel” numbers. The phenomenon has been intriguing neuroscientists for years and this research could unlock new doors to understanding how our brains process sensory input.

Scientists have observed that synesthesia seems to run in families before.  Now, researchers from the University of Cambridge and the Max Planck Institute for Psycholinguistics confirmed that there is almost certainly a genetic component to the condition and described the broader mechanism of action in their study published in the journal Proceedings of the National Academy of Sciences.

“We knew that our genetics can influence other aspects of perception, like the intensity of pain or bitter flavors, but connections between senses like in synesthesia have been harder to study,” Amanda Tilot, lead author of the research and a geneticist at the Max Planck Institute, told Seeker.

Many of the previous brain imaging studies have demonstrated that people with synesthesia process sensory input in a different way to those without the condition. One question stayed open and intrigued scientists – how the perceptual differences develop in the first place?

“We hope our results will help us get closer to bridging the gap between knowing that synesthesia is at least partially genetic and knowing how the brains of adult synesthetes are wired a little differently compared to non-synesthetes,” said Tilot.

Recent advances in genome sequencing provided researchers with the possibility to track three different families in which three or more generations have experienced color when listening to sounds.  At least five members were affected with auditory-visual synesthesia.

“Each of the synaesthetes in the families had sound-color synesthesia,” Tilot said. “Their experiences were confirmed using a test where they listened to sounds and chose which color they associated with what they heard. The sounds were repeated in random order, so we could see if they were consistent in matching certain sounds with particular colors.”

The research group searched for genetic clues that would explain the phenomenon. They analyzed individual DNA samples and detected rare DNA changes in each family. Researchers also noted the similarity in the way synesthesthetic brains handle axonogenesis – an essential process for neuronal connections within and across brain regions.

The research group and Tilot would like to expand the project. Their goal is to study all known forms of synesthesia.

“Some synaesthetes describe numbers, for example, as having specific personalities – this is called ordinal-linguistic personification,” she said. “In one rarer form, words can be connected to specific tastes, a type called lexical-gustatory synesthesia.”

The researchers from the Max Planck Institute for Psycholinguistics are looking for more volunteers:

“Although we studied families where several people all experience the same form of synesthesia, there are lots of people who are synesthetic but do not have a family history of synesthesia,” she said. “We are currently studying hundreds of unrelated people who link colors with letters or numbers, to learn about the genetics of synesthesia from a different angle.”

Learn more about synesthesia in the video below:

Do you want to see what it’s like to hear colors? Watch the video below:

By Andreja Gregoric, MSc