This month, The Clinical Neuropsychologist published a study showing that a region of the brain important for cognitive and motor control was smaller in preschoolers (ages 4 and 5) with attention-deficit hyperactivity disorder than in typically developing children of the same age range. The study was among the first to use magnetic-resonance-imaging technology to examine the brain structures of children under age 7, the official upper age limit to diagnose ADHD.
ADHD is the single most-common child behavioral diagnosis, affecting approximately 2 million children. By age 4, as many as 40 percent of children have sufficient problems with attention to be of concern to parents and preschool teachers.
Researchers analyzed high resolution MRI brain images in 26 preschoolers, 13 with ADHD symptoms and 13 without, and found differences in the caudate nucleus, a group of nerve cells in the subcortical region of the brain that is associated with cognitive and motor control.
Results showed that children with ADHD symptoms had significantly smaller caudate nuclei compared with the children who did not present with ADHD symptoms.
"Clinically, this abnormal brain development sets the stage for the symptoms of ADHD that contribute to cognitive challenges and problems in school," said Dr. Mark Mahone, lead author and Director of Neuropsychology at the Kennedy Krieger Institute, in Baltimore. "Earlier identification and treatment of children presenting with attention problems in the preschool years may minimize the impact of ADHD in the long-term."
As Education Week has previously reported, scientists have observed that the prefrontal cortex of children with ADHD tends to develop more slowly than that of normally developing peers. This study examined a different part of the brain's anatomy than the earlier research--a structure deeper inside the brain.
The researchers will continue to follow the brain development of these children to determine if abnormalities persist or regress with age. Right now it's unknown whether this brain difference represents a developmental delay or a permanent abnormality.