People who learn to read as adults show profound changes in deep structures of the brain, according to a new study. The findings may change researchers’ perspectives on the extent of plasticity in the adult brain, the study said.
In the study, researchers recruited a group of completely illiterate women from villages in northern India and taught them to read. The women also underwent brain scans, both before and after they learned to read.
The researchers, to their surprise, observed changes in deep, evolutionarily old structures of the brain that were thought to be rather inflexible in adults.
“What previously has been found is that changes occur in the outer layer of the brain, in the cortex,” said Falk Huettig, a senior investigator at the Max Planck Institute for Psycholinguistics in the Netherlands, who led the study, published May 24 in the journal Science Advances. “But what was quite surprising [was] that even the very deep structures, such as the thalamus and the brain stem, change and couple their activity with the outer layers of the brain.”
The thalamus works to filter visual information and helps one of those outer layers, the visual cortex, pick out the important bits even before people consciously perceive the information. The better the coordination between the thalamus and the visual cortex, the better a person’s reading performance, Huettig told Live Science.
The women in the study were all at least 30 years old and all were able to achieve a level of reading ability similar to that of a first grader in only six months. As the women’s reading skills improved, the exchange of information between their thalami and cortices became more efficient, the researchers found.
“We knew that children’s brains are very flexible, and that’s why they are so much better in learning foreign languages, for example, than adults,” Huettig said. “However, what we found in this study [is] that even adults’ brains are still very flexible and adaptable for the learning of new skills, and the extent in which this is possible was quite surprising.”
The researchers focused on reading because it’s a rather new skill from the perspective of human evolution, they said. Humans started using written words only 5,000 years ago, which means the human brain — which had evolved over the course of several million years previously — does not have structures specialized to support reading. Instead, when humans started reading, structures that had developed in response to other environmental pressures began to cooperate and adapt, allowing the understanding of written words, the researchers said.
“We are trying to understand, on the basic level, how the brain works and functions,” Huettig said. “One of the ways to do it is to look at these cultural inventions and what changes in the brain when it adapts to these completely new things.”
However, the new study was aimed at more than just gaining a better theoretical understanding of how changes in the brain may work, he said. The researchers also wanted to gain more insight into disorders, such as dyslexia, that develop when the brain circuitry cooperates in less optimal ways, Huettig said.
“In previous studies, we observed that people with dyslexia show abnormalities in these areas deep inside the brain, compared to people who read normally, he said. “But our study shows that these abnormalities are probably not the cause of dyslexia. These differences in these brain structures are essentially just a function of reading experience.”
That means that the more a person reads, the better the various brain areas involved in reading may synchronize their activity, and the better the person will become at reading, Huettig said.
“There still must be a cause of dyslexia, but quite a lot of differences between people who read very well and people who don’t read very well is [explained] just [by] experience,” he said. “That means that everybody should be encouraged to read as much as possible, even if it’s a challenge.”