Genetic basis of synethesia shown to relate to ability of neurons to form connections in the brain

By Tereza Pultarova

About 4 percent of the people on Earth experience a mysterious phenomenon called synesthesia: They hear a sound and automatically see a color; or, they read a certain word, and a specific hue enters their mind’s eye. The condition has long puzzled scientists, but a small new study may offer some clues.

The study, published March 5 in the journal Proceedings of the National Academy of Sciences, offers insight into what might be happening in the brains of people with synesthesia.

Previous “studies of brain function using magnetic resonance imaging confirm that synesthesia is a real biological phenomenon,” said senior study author Simon Fisher, director of the Max Planck Institute for Psycholinguistics in the Netherlands. For example, when people with synesthesia “hear” color, brain scans show that there’s activity in the parts of the brain linked to both sight and sound, he said. (Not all people with the condition “hear” sights, however; the condition can also link other senses.)Indeed, the brains of people with synesthesia previously have been shown to be more connected across different regions than the brains of people whose senses are not cross-linked, Fisher told Live Science. The question, however, was what causes this different brain wiring, he said.

To answer that question, Fisher and his team looked to genetics.

Synesthesia frequently runs in families, so the researchers decided to look for genes that might be responsible for the development of the condition. They chose three families, in which multiple members across at least three generations had a specific type of synesthesia, the so-called sound-color synesthesia, meaning that hearing sounds evokes perceptions of colors. Typically, a specific sound or musical tone is consistently associated with a specific color for people who have this type of synesthesia. However, different members of a single family can see different colors when hearing the same sound, Fisher said.

The scientists used DNA sequencing to study the participants’ genes, Fisher said. Then, to identify genes that might be responsible for the condition, the scientists compared the genes of family members with synesthesia to the genes of family members without it, he said.

But the findings didn’t yield a straightforward result: “There was not a single gene that could explain synesthesia in all three families,” Fisher said. Instead, “there were 37 candidate variants,” or possible gene variations, he said.

Because the study included only a small number of people, there wasn’t enough data to single out the specific genes, of the 37 possibilities, that played a role in synesthesia. So, instead, the scientists looked at the biological functions of each gene to see how it could be related to the development of the condition. “There were just a few biological themes that were significantly enriched across the candidate genes identified,” Fisher said. “One of those was axonogenesis, a crucial process helping neurons get wired up to each other in the developing brain.” Axonogenesis refers to the development of neurons.

This is consistent with prior findings of altered connectivity in brain scans of people with synesthesia, Fisher said. In other words, the genes identified in the study play a role in how the brain is wired, offering a potential explanation for why the brains of people with synesthesia appear to be wired differently.

Brain Connections Set Creative Thinkers Apart

By Tereza Pultarova

Being creative is all about making connections — in your brain, that is.

In a new study, scientists found that the brains of highly creative people have more connections among three specific regions compared to the brains of less creative thinkers. Plus, the more-creative brains were better able to fire up these regions in coordinated way compared with other brains.

The three brain regions are ones that scientists understand well, said lead study author Roger Beaty, a postdoctoral fellow studying cognitive neuroscience at Harvard University. They include the default network, which is involved in spontaneous thinking and imagination; the salience network, which picks up on important information from the environment; and the executive control network, which is involved in cognitive control functions and evaluation.

And though the default network seems like it should be the key source of creativity, people need the salience and the executive control networks to act as a sort of inner critic that judges whether ideas are any good or useful for the given task, Beaty told Live Science.

“You have these three different systems that are all located in different parts of the brain, but they are all co-activated at once,” Beaty said. “People who are better able to co-activate them [came] up with more-creative responses.”

To measure creativity and brain connections, the researchers scanned the brains of about 160 participants using functional magnetic resonance imaging (fMRI), a tool that monitors brain activity by measuring changes in blood flow in various areas the brain. With their heads inside the scanner, the participants were asked to perform a creative-thinking task called divergent thinking. This involves coming up with creative ways to use common objects, such as a knife, a cup or a brick.

“Just thinking about new and unusual ways to use these [objects] has been shown to be a valid way of [measuring] creative thinking,” Beaty said.

The researchers found that performing the divergent-thinking task simultaneously activated the three different networks in the brain. And the greater the interconnectedness and synchronization of these three networks, the better the performance in the divergent-thinking task. In other words, the more connected and in-sync the brain is, the better it does on a creative task.

After establishing what distinguishes creative people’s brains from those of their less creative peers, the researchers wanted to see whether they could reverse the process and use brain activity as a predictor of creative performance.

“We had data sets of previously published studies were people were doing similar creative thinking tasks, and we wanted to see whether someone with weak connectivity in [these networks] has less-creative ideas than someone with stronger connectivity,” Beaty said. “And that’s what we found across three data sets.”

The researchers are now planning to look for similar patterns of brain activity in specific areas of creativity such as writing or music, Beaty said. In addition, the scientists want to find out if the brain activity can in fact change as people become more proficient at certain skills, he said.

The study was published today (Jan. 15) in the journal Proceedings of the National Academy of Sciences.