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In human evolution, reading and writing are relatively recent capabilities. Consequently, to comprehend written language, our brains have had to adapt parts of the visual system to connect with language-processing centers. This adaptation was long believed to mostly happen in the cerebral cortex, the brain's outer layer. However, a recent study involving illiterate adults in their thirties who learned to read over a six-month period revealed that reading activates even deeper brain regions, providing new insights into how we learn and potential treatments for dyslexia. Their findings were published in the journal Science Advances.
Falk Huettig, one of the researchers at the Max Planck Institute for Human Cognitive and Brain Sciences, explains via email to Mytour: "In order to learn to read, the brain must undergo a sort of recycling process. Areas that evolved for recognizing complex objects, like faces, become involved in converting letters into language."
To investigate this process, the researchers chose participants from India, where the literacy rate is approximately 63 percent, a figure impacted by poverty, which limits educational opportunities, especially for girls and women. The majority of participants in this study were women in their thirties who began the study unable to read a single word.
The participants were split into two groups: one group received reading training, while the other served as a control and received no training. Both groups underwent functional magnetic resonance imaging (fMRI) scans of their brains before and after the six-month study. Some participants were excluded due to incomplete scanning sessions, leaving 30 participants in the final analysis.
The participants were taught to read Devanagari, the script that forms the basis of Hindi and other South Asian languages. This alpha-syllabic script consists of intricate characters that represent whole syllables or words.
The instruction was provided by a professional teacher who adhered to the region’s standard method of teaching reading. In the first month, participants learned to read and write 46 basic Devanagari characters simultaneously. After mastering the letters and reading simple words, they proceeded to learn two-syllable words. In total, they studied about 200 words during the first month.
By the second month, participants began reading and writing simple sentences, and by the third month, they progressed to more complex three-syllable words. In the latter half of the program, they were introduced to fundamental grammar rules. "For example, participants learned to distinguish between nouns, pronouns, verbs, proverbs, and adjectives, and also about basic rules of tense and gender," Huettig explains.
After six months, participants who had started with a vocabulary of zero to eight words had achieved a first-grade reading level, according to Huettig. "The process was truly remarkable," he says. "Learning to read is a complex skill, as arbitrary script characters must be linked to the corresponding units of spoken language."
When the researchers examined the brain scans before and after the six-month training, Huettig explains that they initially expected to find results consistent with past studies: that changes would be confined to the cortex, which is known for adapting quickly to new challenges.
However, what surprised them was the discovery of changes in deeper regions of the brain. "We found that the learning process triggers a reorganization that reaches into deeper brain areas, such as the thalamus and the brainstem." More specifically, learning to read affected the superior colliculus in the brainstem and the pulvinar in the thalamus, which "adjust their activity timing to align with that of the visual cortex," Huettig explains.
These deeper brain regions assist the visual cortex in filtering essential information from the overwhelming flood of visual input, even before we consciously register it. "It appears that these brain systems refine their communication as learners become increasingly skilled in reading," he adds.
In essence, the more the participants read, the better they became at it. The study also revealed that the adult brain is more adaptable than previously believed. "Even learning to read in your thirties significantly reshapes brain networks," says Huettig. "The adult brain is incredibly flexible in adapting to new challenges."
Even more encouraging, these findings offer new insights into a potential cause of dyslexia, a language-processing disorder that researchers have long associated with dysfunctions in the thalamus. Since just a few months of reading training can alter the thalamus, Huettig suggests, "it could be that individuals with dyslexia exhibit different brain activity in the thalamus due to a less well-trained visual system compared to that of proficient readers."
Huettig believes that the social impact of this research is enormous, not only for individuals with dyslexia but also for the hundreds of millions of adults worldwide who are either completely or functionally illiterate. He suggests that the new findings could help "develop literacy programs with the best chance of success in supporting these individuals."
