A study of people who learned to read in their thirties has found that the new skill changed their brains, and some of the differences were much deeper inside than anticipated. The discovery may change the way we understand dyslexia, and perhaps change educational responses to the condition.
As animals evolve skills, parts of the brain become allocated to their operation. However, reading and writing are so recent in our evolutionary history, we have no region specifically devoted to this enormously important capacity. Instead, regions previously devoted to tasks such as facial recognition gained a dual purpose, and others had to act as bridges between our visual and language systems.
"Until now it was assumed that these changes are limited to the outer layer of the brain, the cortex, which is known to adapt quickly to new challenges," said Dr Falk Huettig of the Max Planck Institute for Psycholinguistics in a statement.
The brains of young children develop so fast that identifying which changes are brought on by the process of learning to read is almost impossible, but that is not the case for adults. Huettig teamed up with Indian scientists tackling the high rate of illiteracy among Indian women.
A group of 21 adults from northern Indian villages, all but one being women in their late twenties or thirties, were offered basic reading education, in return for having functional Magnetic Resonance Imaging (fMRI) scans conducted before and afterward. At the start of the program, most subjects could not read a single written word of Hindi, their native language, and none could read more than eight words. By the end, they were reading at a first-grade level. This development took just six months, despite Hindi being written in the Devanagari script, which has 46 primary characters and combines them in complex ways.
Science Advances reports that changes were seen not just in the expected places in the outer brain, but in much older regions. "We observed that the so-called colliculi superiores, a part of the brainstem, and the pulvinar, located in the thalamus, adapt the timing of their activity patterns to those of the visual cortex," said first author Dr Michael Skeide of the Max Planck Institute for Human Cognitive and Brain Science. The function of these structures is to filter important information received by our eyes so we notice what is important.
As the subjects' reading improved, signal timing between brain regions aligned, which Skeide said indicates an ability to navigate efficiently through text. Similar changes were not seen among the nine controls who were not taught to read.
Thalamus dysfunctions have been blamed for dyslexia, but Skeide said the rapid modifications to the thalamus throw this into question. “Beginning readers appear to train their subcortical sensory and attentional systems intensively,” the paper argues. The authors think the reason dyslexics have different thalamus brain activity may be because this region is less well trained, since their struggles to read mean there has been less opportunity to rewire the brain. It's possible, then, that neural pathways connecting the thalamas with other sections of the brain may be responsible. Huettig proposed assessing children before they learn to read to see if those who subsequently develop dyslexia show differences in the thalamus from the start.
The program initially enrolled another 21 participants, 12 of them as controls, who were dropped as a result of being unable to complete the scanning tests, or producing unclear fMRI data. Those unable to conduct the scans generally showed higher non-symbolic intelligence and had fewer literate family members, but the authors are not sure of the reasons for these failures, or if there is anything to learn from them.