These differences are visible when more fit kids are reading straightforward sentences or sentences that contain errors of grammar or syntax. (Agencies)
The new findings, however, do not prove that higher fitness directly influences the changes seen in the electrical activity of the brain, the researchers say.
Although, it offers a potential mechanism to explain why fitness correlates so closely with better cognitive performance on a variety of tasks.
"All we know is there is something different about higher and lower fit kids. Whether that difference is caused by fitness or maybe some third variable that (affects) both fitness and language processing, we do not know yet," explained Professor Charles Hillman from the University of Illinois.
The researchers used electroencephalography (EEG), placing an electrode cap on the scalp of children to capture some of the electrical impulses associated with brain activity.
The readouts from the electrodes look like seismic readings captured during an earthquake, and characteristic wave patterns are associated with different tasks.
"These patterns are called 'event-related potentials' (ERPs) and vary according to the person being evaluated and the nature of the stimulus," said Scudder, a graduate student from Professor Hillman's team.
For example, if you hear or read a word in a sentence that makes sense ("You wear shoes on your feet"), the component of the brain waveform known as the N400 is less pronounced than if you read a sentence in which the word no longer makes sense ("At school we sing shoes and dance," for example).
The researchers also looked at another ERP, the P600, which is associated with the grammatical rules of a sentence.
They found that children who were more fit (as measured by oxygen uptake during exercise) had higher amplitude N400 and P600 waves than their less-fit peers when reading normal or nonsensical sentences.
"Previous reports have shown that greater N400 amplitude is seen in higher-ability readers," Scudder said.
The results, published in the journal Brain and Cognition, add to a growing body of research that finds strong links between fitness and healthy brain function.
These differences are visible when more fit kids are reading straightforward sentences or sentences that contain errors of grammar or syntax.