New research finds evidence of differences in brain function in kids with attention-deficit/hyperactivity disorder (ADHD) that may underlie problems recognizing emotion in facial expressions.
Children with ADHD frequently exhibit inattention, hyperactivity, and impulsivity. These behaviors may explain why they are often excluded from peer activities, according to researchers led by Ryusuke Kakigi, M.D., Ph.D., of Japan’s National Institutes of Natural Sciences.
The researchers measured changing blood flow in the brain — called hemodynamics — to uncover the neural basis for the recognition of facial expression; they found differences between children with ADHD and typically developing children.
In the study, researchers showed images of a happy expression or an angry expression to 13 children with ADHD and 13 typically developing children and identified the area of the brain the expressions activated.
Investigators used non-invasive near-infrared spectroscopy to measure brain activity. Near-infrared light, which normally passes through the body, was projected through the skull and the absorbed or scattered light was measured.
The strength of the light depends on the concentration of oxyhemoglobin — the oxygen-loaded form of hemoglobin, the predominant protein in red blood cells — which fuels the active neurons.
Typically developing children showed significant hemodynamic response to both the happy expression and angry expression in the right hemisphere of the brain.
But kids with ADHD had a significant hemodynamic response only to the happy expression; there was no specific brain activity seen for the angry expression.
The researchers suggested this difference might be responsible for ADHD children’s difficulties with social recognition and establishing peer relationships.
The findings are discussed in the online journal Neuropsychologia.