Working memory assessed by functional near-infrared spectroscopy in child patients with attention deficit hyperactivity disorder

Abstract

Objective To study the activation characteristics in the prefrontal cortex(PFC) of children with attention deficit hyperactivity disorder (ADHD) in the working memory tasks by using functional near-infrared spectroscopy(fNIRS). Methods In this study, 12 children with ADHD and 13 typically developing children were studied. N-back task was chosen as the neuropsychology task. The functional blood oxygen metabolism signals and the correct number of key-press were recorded when the children performed n-back task by using fNIRS. The average change of the hemoglobin concentration and the correct number of keys were compared by t test. Results (1) In the behavior data, ADHD children had a lower correct number of key-press compared with typically developing children at both 0-back and 1-back task conditions (0-back: t=-2.222, P=0.043; 1-back: t=-3.276,P=0.005). (2)For the 0-back task condition, there was no statistical difference between the two groups. For the 1-back task condition, task-related increment of the oxygen-Hb concentration, the marker of cortex activation, in ADHD children was significantly smaller than the typically developing children for channel 18, which was located in left dorsolateral prefrontal cortex (DLPFC) (ADHD children: (0.022±0.040) mmol/(L·mm); Typical Developing Children: (0.085±0.040) mmol/(L·mm); t=3.88,P<0.05). Conclusions The PFC activation in ADHD children may be significantly decreased, which probably indicates a working memory defect in ADHD children. Key words: Attention deficit disorder with hyperactivity; Spectroscopy, near-infrared; Child; Working memory