Researchers move closer to pinpointing age of brain activity changes related to language

The number of sites in children's brains involved in language recognition decreases as the children age, according to a University of Cincinnati (UC) study.

The finding, says Jerzy Szaflarski, MD, PhD, an assistant professor of neurology at the UC Academic Health Center, suggests that as a child grows more language proficient, recalling words may involve less effort.

It also supports earlier explanations as to why young children who injure a large part of one side of the brain often recover completely, or almost completely.

Funded by the National Institute of Child Health and Human Development, the study will be presented April 6 at the annual meeting of the American Academy of Neurology in San Diego. The paper will also appear in print in the April Annals of Neurology.

"The decrease in activity sites may mean that language areas in the brain are more flexible when children are younger and become more specialized as they mature," Dr. Szaflarski says.

"This raises hope for rehabilitation of brain function in children after stroke or traumatic brain injuries," he says.

Dr. Szaflarski and senior coauthor Scott Holland, PhD, a UC professor who also heads pediatric brain-imaging research at Cincinnati Children's Hospital Medical Center, led a study of 30 children, starting when they were aged 5, 6 and 7. For five years they monitored the children's responses using functional magnetic resonance (fMRI) brain imaging, a technique that shows what part of the brain "lights up" with activity during a specific exercise.

They concluded that more brain areas are involved during a language exercise in a 5-year-old than in an 11-year-old.

The children used in the study were healthy, native English-speakers. During fMRI scanning, each child was given a list of nouns and told to think of verbs or actions that would go with them. For example, the word "ball" could have "throw" or "kick" before it.

The children listened through earphones as the words were read to them five seconds apart. The fMRI monitored their brain activity as they silently thought of actions associated with the words.

To break the chain of thought associated with individual words, the children were told to tap their fingers after each one--giving researchers a control to separate each brain scan during verb generation.

The fMRI images showed larger areas and more sites of activity in the brains of the younger children. "But, as the child's brain matured," Dr. Holland says, "the number of activity sites decreased and concentrated more on the left side of the brain."

The researchers' earlier studies of both children and adults showed that language-related brain activity increased on the dominant side of children's' brains, which is typically the left side in right-handed people. Adults over 25 showed a decrease in language-related brain activity on the dominant side and a more even pattern in both sides of the brain.