- In most adults, processing language only happens in the left hemisphere
- In very young children, however, language can often be recovered even if the left hemisphere is badly damaged
- This is very good news for young children who experience a neural injury
Adults process language on one side of the brain, but kids use both hemispheres, a new study suggests.
The finding might explain why children recover more easily from brain injuries than adults, the study authors added.
"This is very good news for young children who experience a neural injury," said researcher Elissa Newport. She's a neurology professor at Georgetown University Medical Center in Washington, D.C.
"Use of both hemispheres provides a mechanism to compensate after a neural injury," Newport said in a Georgetown news release. "For example, if the left hemisphere is damaged from a perinatal stroke – one that occurs right after birth – a child will learn language using the right hemisphere. A child born with cerebral palsy that damages only one hemisphere can develop needed cognitive abilities in the other hemisphere. Our study demonstrates how that is possible."
Both hemispheres involved
In nearly all adults, processing sentences is only possible in the left hemisphere. But in very young children, language can be recovered in many patients even if the left hemisphere is severely damaged.
"It was unclear whether strong left dominance for language is present at birth or appears gradually during development," Newport noted.
Using functional MRI (fMRI), the researchers showed that adult language patterns are not established in young children, where both hemispheres are involved in language during early development.
For the study, the researchers enrolled 39 healthy children, aged 4 to 13; and 14 adults, aged 18 to 29.
The participants were given a sentence comprehension task. The researchers analysed fMRI activation patterns in each hemisphere of the participants' brains.
The investigators then compared the language activation maps for children and adults. They also looked at the whole brain to identify areas where language activation was correlated with age.
Enhancement of right hemisphere
The findings showed that even young children had left-brain language activation. Many of the youngest children also had activation in the right hemisphere.
In adults, the right hemisphere is activated while processing emotions expressed with the voice. In young children, however, areas in both hemispheres were each activated in the meaning of sentences and emotion.
If researchers could do the same analysis in even younger children, "it is likely we would see even greater functional involvement of the right hemisphere in language processing than we see in our youngest participants (ages four to six years)," Newport said.
"Our findings suggest that the normal involvement of the right hemisphere in language processing during very early childhood may permit the maintenance and enhancement of right hemisphere development if the left hemisphere is injured," she said.
The report was published online in the Proceedings of the National Academy of Sciences.