Ka-Ka-Ka-r-r-r-et-et-et: Carrot. For parents helping their children learn to read, sounding out words like that is a daily occurrence. Letter-by-letter, syllable-by-syllable, kids make the sounds before thinking about the meaning of the words. As they become reading proficient, they can recognize the words without this painstaking process.
The path that children take to reading proficiency is enabled by changes in the physical structure of the brain – with gray matter waning in some areas as the brain becomes more efficient at particular reading skills, researchers have found. In a new study that followed first graders for two years, neuroscientists have found that the most proficient readers started with increased gray matter for speech processing and, as they became better readers, regions of the brain associated with sounding out words decreased in volume – leading to the possibility that unnecessary neural connections are eliminated to make them more efficient readers.
Given evidence that the brain adapts to the learning of new skills via plastic structural changes, we were curious to examine which structural changes are related to the acquisition of written language,” says Janosch Linkersdörfer of the German Institute for International Educational Research in Frankfurt. He was fascinated by the fact that people can acquire complex reading and math skills that are recent cultural inventions and, therefore, lack dedicated neural systems. Although scientists have explored the neural processes that support reading, few have determined how the brain itself changes to learn how to read.
So Linkersdörfer and colleagues from Frankfurt University invited children to come into their lab at two different times in their reading lives – in the first and second years of elementary school. Each year, the children participated in a behavioral assessment of their reading skills and a structural MRI session. Using a technique called “tensor-based morphometry” which can very accurately align 3-D images of the brain, the researchers mapped out differences between gray matter volume at the two different time points and matched those changes to reading proficiency scores.
As published in the Journal of Cognitive Neuroscience, they found two major patterns in their data: First, they found that children with higher volumes of gray matter in a left hemispheric region that has been associated with the perception and production of speech sounds became more reading proficient in second grade than those with correspondingly lower gray matter volumes. They believe the results are evidence that children have significant individual neurostructural differences before they learn how to read.
The other major result they found was a decrease in gray matter volume as children transitioned from being reading ready in first grade to being more reading proficient in second grade. These decreases in gray matter were in regions known to be involved in the manipulation of speech sounds. As children become better readers, they rely less on sounding out every word and are able to use their neural networks more efficiently.
We were surprised to find a negative association between cortical volume changes and reading proficiency,” says Linkersdörfer. “Previous studies that examined neurostructural correlates of reading, mostly in adults, usually reported positive associations between structural features of the brain and reading proficiency.” But, he points out, this study is the first to look at such structural changes over more than one time point in a child’s life.
This new study, Linkersdörfer says, also examined children much younger than has been typical of such studies – looking at children at the very beginning of reading instruction. “In children of this age group, neurostructural development is mainly dominated by synaptic pruning processes,” whereby experience guides the strengthening of frequently used neural connections and the weakening or elimination of sparsely used connections.
This phase might mark a shift toward a more accurate and efficient – more adult-like – processing in specialized neural networks,” he says. “Our results might thus indicate the formation of a more mature and fine-tuned cortical network for the processing of written language in the left hemisphere.”
Importantly for parents and children alike, the study supports the idea that the brain is highly malleable and adapts to external demands. Therefore, reading success depends on the amount of effort put in.
It also, however, points to structural brain differences that might give some children a leg up in the reading process. “It will be important to investigate whether these differences reflect genetic predispositions or differences in speech and language experience in the first years of life,” Linkersdörfer says.
In future studies, Linkersdörfer’s team will follow children over longer periods of time to further examine how the brain dynamically changes over different stages of reading development. They are also interested in conducting similar studies with other academic skills such as mathematics. “Ultimately, we hope that our work will contribute to a better understanding of how the brain adapts to facilitate these academic skills,” he says.
-Lisa M.P. Munoz
The paper, “The Association between Gray Matter Volume and Reading Proficiency: A Longitudinal Study of Beginning Readers” by Janosch Linkersdörfer, Alina Jurcoane, Sven Lindberg, Jochen Kaiser, Marcus Hasselhorn, Christian J. Fiebach, and Jan Lonnemanm, was published in the Journal of Cognitive Neuroscience online on Sept. 9, 2014.