Children who are physically fit have faster and more robust
neuro-electrical brain responses during reading than their less-fit peers,
researchers report.
These differences correspond with better language skills in
the children who are more fit, and occur whether they're reading
straightforward sentences or sentences that contain errors of grammar or
syntax.
The new findings, reported in the journal Brain and
Cognition, do not prove that higher fitness directly influences the changes
seen in the electrical activity of the brain, the researchers say, but offer 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," said University of Illinois kinesiology and
community health professor Charles Hillman, who led the research with graduate
student Mark Scudder and psychology professor Kara Federmeier. "Now
whether that difference is caused by fitness or maybe some third variable that
(affects) both fitness and language processing, we don't know yet."
The researchers used electroencephalography (EEG), placing
an electrode cap on the scalp to capture some of the electrical impulses
associated with brain activity. The squiggly 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, Scudder said.
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), Scudder said.
"We focused on the N400 because it is associated with
the processing of the meaning of a word," he said. "And then we also
looked at another ERP, the P600, which is associated with the grammatical rules
of a sentence." Federmeier, a study co-author, is an expert in the
neurobiological basis of language. Her work inspired the new analysis.
The researchers 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. The
N400 also had shorter latency in children who were more fit, suggesting that
they processed the same information more quickly than their peers.
Most importantly, the researchers said, these differences in
brain activity corresponded to better reading performance and language
comprehension in the children who were more fit.
"Previous reports have shown that greater N400
amplitude is seen in higher-ability readers," Scudder said.
"Our study shows that the brain function of higher fit
kids is different, in the sense that they appear to be able to better allocate
resources in the brain towards aspects of cognition that support reading
comprehension," Hillman said.
More work must be done to tease out the causes of improved
cognition in kids who are more fit, Hillman said, but the new findings add to a
growing body of research that finds strong links between fitness and healthy
brain function.
Many studies conducted in the last decade, on children and
older adults, "have repeatedly demonstrated an effect of increases in
either physical activity in one's lifestyle or improvements in aerobic fitness,
and the implications of those health behaviors for brain structure, brain
function and cognitive performance," Hillman said.
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