Effect of Atomoxetine Hydrochloride on Working Memory in Children with ADHD: A Functional Near-infrared Spectroscopy Study

Objective: This study aimed to investigate the effect of atomoxetine hydrochloride (ATX) on the activation of the prefrontal complex (PFC) in children with ADHD during a working memory task. Methods: We recruited 14 drug-naive children with ADHD. PFC functional blood oxygen was recorded by using fNIRS during the n-back task. Clinical symptoms were assessed by parents using the Swanson, Nolan, and Pelham-IV rating scale and Conners measuring scale (parent symptom questionnaire) at the same time. After 8 weeks of treatment with ATX, these children were re-evaluated by using fNIRS, SNAP-IV, and Conners scales. Statistical methods were used to compare the physiological and psychological test indicators in the pre- and post-ATX conditions. Simultaneously, oxygenated hemoglobin concentration variation and the scores of the two scales were used as indicators for correlation analysis between PFC activation and clinical symptoms. Results: Based on the performance data, children showed higher accuracy and lower omission error during the n-back task after ATX treatment. According to fNIRS data, the hemodynamic changes between pre-ATX and post-ATX conditions suggested that high-level activation in channel 36 was found in children under post-ATX conditions. The associated channels were located in frontopolar PFC, dorsolateral PFC, and orbitofrontal cortex. Enhanced trends were also found in channels 5 and 7. Regarding the rating scale scores, children under post-ATX conditions showed relatively lower inattention scores, hyperactivity scores, oppositional defiant score, and total scores on the SNAP-IV scale. Lower conduct problem score, learning problem score, hyperactivity-impulsivity score, and hyperactivity index of Conners measuring scale were observed in children who received treatment. These values were statistically and significantly different. A significantly negative correlation was observed between oxygenated hemoglobin concentration changes and the total score on the SNAP-IV scale. Conclusions: fNIRS is a helpful tool for identifying the effects of ATX on children with ADHD, and its combination with the SNAP-IV scale can provide an objective physiological index for evaluating the efficacy of ATX．ATX can improve the core symptoms and executive function of children with ADHD.