Working memory in children with attention deficit hyperactivity disorder:a near-infrared spectroscopy study

Objective To investigate the working memory profiles in children with Attention Deficit Hyperactivity Disorder(ADHD).Methods We investigated 39 children with ADHD(DSM-IV),including ADHD combined type(ADHD-C)(n = 14),ADHD inattentive type(ADHD-I)(n = 14)and ADHD hyperactive/impulsive type(ADHD-HI)(n = 11),and 19 normal controls matched for age,sex,handedness,and intelligence during a working memory task.Prefrontal brain activity was measured by concentration changes of oxygenated haemoglobin(oxyHb).Functional near-infrared spectroscopy(NIRS)was used to obtain the oxyHb.Results The results of working memory task:(1)ADHD children had more total errors(3.51±3.025)and comparison errors(2.41±2.149)than controls(P 0.05).(2)There was no significant difference in reaction time between ADHD and control group(P0.05).(3)ADHD-C patients had more reaction errors(1.71±2.016)than ADHD-HI's(P 0.05);on comparison errors,ADHD-HI children had more than ADHD-C's(P 0.05),and ADHD-I children also had more than ADHD-C's(P 0.05).But there was no significant difference between ADHD-I and ADHD-HI group.(4)ADHD-HI group had longer reaction time than ADHD-I's(P 0.05).The results of NIRS:(1)There was no significant difference in concentration changes of oxygenated haemoglobin(oxyHb)between ADHD and control group when they performed working memory task.(2)Concentration levels of oxyHb in ADHD-C decreased in the left-down prefrontal cortex area during performing reaction commission than ADHD-I[(-2.46±9.62)×10-4 vs.(10.47±14.18)×10-4 P 0.05].Conclusion There are significant deficiencies in working memory in children with ADHD;ADHD subtypes differ in working memory profile.