Babies process words using the same brain structures as adults, and in the same amount of time, according to a study by the University of California, San Diego. They are also able to understand words as more than simple sounds and comprehend the meanings of many of the words they hear.
“Babies are using the same brain mechanisms as adults to access the meaning of words from what is thought to be a mental ‘database’ of meanings, a database which is continually being updated right into adulthood,” says first author Katherine E. Travis of the Department of Neurosciences and the Multimodal Imaging Laboratory.
For the study, scientists used MRI and MEG (scan that measures magnetic fields emitted by neurons in the brain) to non-invasively analyze brain activity in infants, ages 12 to 18 months.
It was previously assumed that babies process words with a completely different learning mechanism, and it was believed that learning begins primitively—later evolving into the more “adult way” of learning. It has been difficult for scientists to figure out which areas of the brain are most involved in language learning because there is a lack information on how this process works in the developing brain.
Although lesions in two brain areas — Broca’s and Wernicke’s — have long been associated with loss of language skills in adults, these areas seem to have little impact on language development in early childhood. Some scientists have addressed this anomaly by theorizing that the right hemisphere and inferior frontal regions are vital for childhood language development, and that the other language areas of adulthood become dominant only when language development has matured.
Others have hypothesized that the plasticity of an infant’s brain allows other regions to take over the work of language-learning if the left frontotemporal regions become damaged at a young age.
During the first part of the experiment, the babies listened to words accompanied with sounds that have similar acoustic properties, but no meaning, to see if the infants could determine the difference between the two.
In the second part, the researchers wanted to see if the babies were able to understand the meaning of these words. For example, babies were shown pictures of familiar objects and then heard words that were either the correct or incorrect names for these objects: a picture of a ball followed by the spoken word ball, versus a picture of a ball followed by the spoken word dog.
It was determined through brain images that the infants could detect the mismatch between a picture and a word, as shown by the degree of brain activity. An incorrectly matched word triggered a classic brain response located in the same left frontotemporal areas known to process word meaning in the adult brain. The tests were then given to adults to confirm if the same mismatched picture/word combinations shown to babies would create larger responses in left frontotemporal areas.
“Our study shows that the neural machinery used by adults to understand words is already functional when words are first being learned,” said Eric Halgren, Ph.D., professor of radiology in the School of Medicine.
“This basic process seems to embody the process whereby words are understood, as well as the context for learning new words.”
The scientists believe the results could affect future studies. For example, the development of brain imaging tests could diagnose whether a baby has normal word understanding even before he or she can talk. This could allow early prediction for language disabilities or autism.
Source: University of California