Age Differences in Language Processing

By Melissa Lee Phillips Neuroscience for Kids Consultant June 17, 2002 The human brain undergoes extraordinary changes from embryo to adult. One way to examine such changes is by studying differences in how the brain functions in adults and in children. Although adults' and children's brains work similarly for some tasks, even small physiological differences can shed light on how the brain develops. Understanding these processes may be important for treating childhood disorders such as dyslexia. A study from Washington University in St. Louis, Missouri, shows that children and adults sometimes use different parts of their brains for the same task. The research team led by Bradley Schlaggar used functional magnetic resonance imaging (fMRI) to measure brain activity during a single-word verbal response task. In this task, the subjects looked at individual words on a computer screen. They then responded by speaking a new word, such as a related verb, a word that rhymed, or a word with the opposite meaning of the word seen on the screen. Each person's brain blood flow was measured while performing this task. The scientists observed 21 adults (ages 18-35) and 19 children (ages 7-10) and looked for differences in brain activity.

One problem with some experiments designed to test differences between children and adults is that children tend to be slower and less accurate at language tasks. Therefore, it is difficult to know if the results are due to age differences or simply due to differences in ability. To get around this problem, the researchers looked at children and adults whose abilities were the same. They assumed that if the adults and the children were equally good at the task, then any variations in brain activity would be due only to age. The scientists found two major differences in the brain activity of children and adults. The children had more activity in the left extrastriate cortex and the adults had more activity in the left frontal cortex. Both of these areas are known to be important in language processing. This is the first study to show that adults and children may be using these brain areas differently. Studies such as these are important to learn how adult human brains develop. By comparing young and old brains, researchers can begin to piece together a timeline of brain development. This knowledge may someday help in understanding and treating many developmental brain disorders.

Approximate location of differences in brain activity between adults and children.