New research challenges the previously held belief that infants' brains don't divide into left-brain/right-brain dominance until puberty. A new study finds the brain's left hemisphere plays the leading role in processing most language functions beginning almost immediately after birth.
Researchers are using functional magnetic resonance imaging, or fMRI, to study infant brain activity in response to speech. They say this is the first time fMRI has been used to study infants. It is a noninvasive way to study neuronal responses, and the doctors say it does not use radiation or pharmaceutical injections.
Infants were asleep during the procedure, but not sedated. The infants listened to tapes consisting of scanner noise, nonsense speech, and "motherese" speech. Doctors found definite left-side-dominant activation patterns when the infants heard speech as opposed to when they heard scanner noise. This test, however, was not able to determine whether the infant brains were able to distinguish between the two types of speech.
Prior to this study, most doctors thought the left-dominance in response to speech was not fully developed until puberty. This study seems to show that language lateralization -- the localization of a speech to the right of left side of the brain -- is established almost from birth.
This specific study was conducted as part of a larger, ongoing study monitoring the cognitive development of infants with brain injury from birth to age 2. The researchers performed the fMRI exams on 42 infants with documented brain injury, but the fMRI analysis only included cases where both sides of the brain were equally capable of developing. Children with brain trauma that was evident on the MR images were excluded.
However specialists feel that a detailed knowledge about the neural mechanisms associated with increasing levels of speech should prove useful in the study of developmental language disorders, which are the single largest handicapping condition of childhood. Specialists also hope that the mapping of specific brain-language relationships will foster understanding of the mental processes underlying language itself.