Abstract
The current study aimed to explore the neural substrate for atomoxetine effects on attentional control in school-aged children with attention deficit hyperactivity disorder (ADHD) using functional near-infrared spectroscopy (fNIRS), which can be applied to young children with ADHD more easily than conventional neuroimaging modalities. Using fNIRS, we monitored the oxy-hemoglobin signal changes of 15 ADHD children (6 to 14 years old) performing an oddball task before and 1.5h after atomoxetine or placebo administration, in a randomized, double-blind, placebo-controlled, crossover design. Fifteen age-, gender-, and intelligence quotient-matched normal controls without atomoxetine administration were also monitored. In the control subjects, the oddball task recruited the right prefrontal and inferior parietal cortices. The right prefrontal and parietal activation was normalized after atomoxetine administration in ADHD children. This was in contrast to our previous study using a similar protocol showing methylphenidate-induced normalization of only the right prefrontal function. fNIRS allows the detection of differential neuropharmacological profiles of both substances in the attentional network: the neuropharmacological effects of atomoxetine to upregulate the noradrenergic system reflected in the right prefrontal and inferior parietal activations and those of methylphenidate to upregulate the dopamine system reflected in the prefrontal cortex activation.
Highlights
Attention deficit hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder of childhood, with a prevalence rate estimated to be between 3% and 7%.1,2 ADHD is characterized with heterogeneous phenotypes, including age-inappropriate inattention, impulsivity, and hyperactivity
Control-subject reaction times (RT) for correct trials were significantly shorter than those of premedicated, postplacebo, and post-ATX ADHD subjects. These results suggest that while RT for correct trials represented the slower behavioral performance of premedicated ADHD children well, it was not normalized by administration of ATX
Control-subject omission error rates for target trials were marginally lower than those for premedicated and post-ATX ADHD subjects, and significantly lower than those for postplacebo ADHD subjects. These results suggest that omission error rates partially reflected the less-correct behavioral performance of premedicated ADHD children, but failed to indicate normalization by ATX administration (Table 2)
Summary
Attention deficit hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder of childhood, with a prevalence rate estimated to be between 3% and 7%.1,2 ADHD is characterized with heterogeneous phenotypes, including age-inappropriate inattention, impulsivity, and hyperactivity. Attention deficit hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder of childhood, with a prevalence rate estimated to be between 3% and 7%.1,2. ADHD is characterized with heterogeneous phenotypes, including age-inappropriate inattention, impulsivity, and hyperactivity. ADHD symptoms are most often identified during early elementary school years.[3,4,5,6] ADHD patients often suffer from academic difficulties and develop antisocial behaviors that result from emotional and social problems associated with ADHD-related core symptoms.[7] The disorder persists into adolescence and adulthood in 65% to 85% of cases, leads to impaired educational and vocational performance, and increases the risk of developing antisocial behaviors that are not directly related to ADHD.[8] ADHD during childhood can robustly predict later depression and suicidal risk in adolescence and adulthood.[9]
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