The man who hunts ducks out on weekends.
If you needed a moment to extract meaning from that sentence, you are not alone. But you probably did grasp the sense rather quickly: The man, who hunts something, ducks out on weekends.
But if you struggle with dyslexia, that hunter may have set your brain buzzing in a nonproductive effort to comprehend. It’s not the words that stump you. It’s the sense, the meaning of the whole sentence.
The neurological basis for that buzz is one of the findings reported in a recent study published in Cerebral Cortex. Investigators Sheryl Rimrodt and Laurie Cutting and their team at the Kennedy Krieger Institute used functional magnetic resonance imaging (fMRI) to examine the brain activity associated with word recognition and sentence comprehension in 29 children ages 9 through 14. Fifteen of the children were typically developing readers; 14 were impaired readers.
While in the scanner, the children decided whether short, six-word sentences were meaningful or nonmeaningful. They also responded to lists of words, indicating when a word was repeated. By comparing the two tasks, Cutting says, “we tried to parcel out the brain activation that was associated with comprehension after accounting for that associated with reading the single words.”
The two groups of children were equally speedy and accurate on the word recognition task but showed important differences when comprehension was assessed. Typically developing readers performed the sentence task better, and they used a tightly coordinated network of brain regions to do it.
In contrast, children with reading disabilities showed diffuse, widespread brain activity as they performed the comprehension task. Their brain scans showed greater activity than those of the normal readers in areas associated with linguistic processing (left middle/superior temporal gyri) and attention and response selection (bilateral insula, right cingulate gyrus, right superior frontal gyrus and right parietal lobe).
The results showed a correlation between increased activity in those brain regions and poorer performance on reading and language tests. The overactivation was driven by the brain’s response to nonmeaningful sentences, the researchers said.
“For nonmeaningful sentences, [children with reading difficulties] weren’t able to process in the same way as typically developing readers,” Cutting says. “That suggests that they do not have the flexibility in their comprehension that typically developing readers do.”
Most past research in this field has focused on the word-recognition capacities of beginning readers, not on the more complex processes of sentence comprehension.
“This is a vital area of investigation,” Cutting says, “because sentence comprehension becomes a critical aspect of reading as children move into fourth grade and are required not just to recognize words, but to learn from the text they are reading.”
“This study provides the first important step to a better understanding of the brain basis for impaired reading comprehension,” says Guinevere Eden, director of the Center for the Study of Learning at Georgetown University Medical Center and president-elect of the International Dyslexia Association. “Future work may also aid in understanding which treatment options are most beneficial to these students,” she says.