Infant Brain Makes Sense of Language
Speech processing at 3 months of age, French study suggests
THURSDAY, Dec. 5, 2002 (HealthDayNews) -- A baby's brain can process language as early as 3 months of age, a French study suggests.
However, the finding doesn't settle a long-running debate about whether the brain is naturally wired to understand language or picks up that ability over time.
"Our results provide evidence that should be accommodated by any model of language development," says Dr. Ghislaine Dehaene-Lambertz, a scientist at the National Center for Scientific Research in Paris.
A report in tomorrow's issue of Science describes how Dehaene-Lambertz and her colleagues used functional magnetic resonance imaging (fMRI) -- which shows what parts of the brain are activated by tracing the flow of blood -- to get a more detailed picture of infants' reactions to speech.
Taking great care to ensure the comfort of their 30 young subjects, the French researchers used fMRIs to measure brain activity as they spoke "sense" and "nonsense" to the 2- and 3-month-olds. The sense consisted of short French sentences; the nonsense consisted of the same sentences, recorded and played back in reverse. Having some sentences played backward was done because some earlier studies found infants just 4 days old could distinguish between a sentence in their native language and a sentence in a foreign language.
Other scientists have done the same kind of study before, but always with babies who were sedated or asleep, Dehaene-Lambertz says. The results have varied. Some tests got the kind of response expected in the adult brain; in others, very young babies showed a different response.
In this study, both the sense and the nonsense activated the left temporal lobe of the brain, which is known to be involved in adult speech processing, the researchers say. However, other parts of the infant brain responded more to the forward-spoken sentences.
"The main thing is that the baby brain is already organized to process speech at that age," Dehaene-Lambertz says. "But maybe it responds to any sound rather than just to speech."
What is certain is that even at 3 months, the infant brain is structured into several functional regions, she says. However, does that mean the brain is equipped with genetically determined mechanisms of language processing, as one side of the debate maintains, or that the infant brain is gradually trained to understand language as it hears words?
"We're not sure if the language-processing ability of the brain is already learned at 3 months or if it is present at birth," Dehaene-Lambertz says. "What we can show is that it is already functioning. Either they have learned something about their native language so they can recognize sentences, or the ability is innate."
More important, the study found the frontal cortex of the infants' brains, the region of advanced thinking processes, was active during the test sessions. This region of the brain "can no longer be assumed to be silent in the first months of life," the report says.
What To Do
Brown University recently did a study on 6-month-old infants and speech.