Processing speed may improve earlier than response inhibition/ interferens in children with ADHD-combined type receiving methylphenidate: a single-center study

The effects of first-dose methylphenidate on the neural signatures of visual selective attention in children with attention-deficit/hyperactivity disorder

Although methylphenidate (MPH) has been shown to significantly improve selective attention in children with attention-deficit/hyperactivity disorder (ADHD), the neural mechanism of this effect remains unclear. We investigated the effects of first-dose MPH on the neural signatures of visual selective attention in children with ADHD. We measured the impact of first-dose MPH on electrophysiological indexes from eighteen children with ADHD (8.9-15.2 years; 15 boys) while they performed a visual search task. MPH was administered in a double-blind placebo-controlled crossover design. MPH led to decreases in behavioral error rates and reaction times. For the electrophysiological indexes, MPH significantly increased the target-elicited N2pc amplitude and posterior P3 amplitude during the selective attention process. The trial-based correlation analysis revealed that the enhanced N2pc (more negative) and P3 (more positive) promoted the behavioral response speed for children with ADHD. The lower individual P3 amplitude was associated with higher severity of inattention symptoms. The severer inattention symptoms were related to weaker MPH effect on N2pc amplitude. These findings suggest that N2pc and P3 are closely related to the mechanism of MPH in the ADHD treatment.

Specific dopaminergic genetic variants influence impulsivity, cognitive deficit, and disease severity of Indian ADHD probands

BACKGROUND

Impulsivity (Imp), being one of the cardinal symptoms of Attention Deficit Hyperactivity Disorder (ADHD), often leads to inappropriate responses to stimuli. Since the dopaminergic system is the primary target for pharmaceutical intervention in ADHD, we investigated the association between ADHD-related Imp and functional gene variants of the dopamine transporter (SLC6A3) and catechol-O-methyltransferase involved in dopamine clearance.

METHODS AND RESULTS

Indo-Caucasoid families with ADHD probands (N = 217) were recruited based on the Diagnostic and Statistical Manual of Mental Disorders (DSM). Imp of the probands was assessed using the Domain Specific Imp Scale for Children and DSM. Peripheral blood was collected after obtaining informed written consent for participation, genomic DNA was isolated, and target sites were genotyped by DNA sequencing. The association of genetic variants with Imp was examined by the Quantitative trait analysis (QTA) and Analysis of variance (ANOVA). Post-Hoc analysis following QTA and ANOVA showed significant associations of rs2254408, rs2981359, and rs2239393 with different domains of Imp (P < 0.05). Various haplotypic combinations also showed statistically significant associations with Imp (P < 0.05). Multifactor dimensionality reduction models revealed strong effects of the variants on Imp. ADHD probands harboring the risk alleles exhibited a deficit in performance during cognitive assessment. Longitudinal follow-up revealed a significant association of rs2254408 with trait persistence.

CONCLUSION

The present study indicates the influence of the studied genetic variants on ADHD-associated imp, executive deficit, and disease persistence. Thus, these variants may be helpful as predictors for the success of individual therapeutic sessions during cognitive training.

The Relationship of Comorbid Overweight-Obesity With Cold Executive Functions, Verbal Short-Term Memory, and Learning in Attention Deficit Hyperactivity Disorder

ABSTRACT

The aim of this study was to investigate the relationship between comorbid obesity/overweight and cold executive functions, verbal short-term memory, and learning in children with attention deficit and hyperactivity disorder (ADHD). Our study was conducted on 100 drug-naive participants, including 70 patients with ADHD and 30 healthy controls. In our study, patients diagnosed with ADHD were divided into two groups according to body mass index as above the 85th percentile and at or below the 85th percentile. Cold executive functions were evaluated by the Stroop Test (ST) and Cancellation Test (CT). Serial Digit Learning Test (SDLT) was administered to measure verbal short-term memory and learning capacity. To evaluate the severity of ADHD objectively, the parents completed the Conners' Parents Rating Scale-Revised Short Version (CPRS-RS). There was no statistically significant difference in ST, SDLT, CT scores, and CPRS-RS subscale scores between the two groups with ADHD. This study show that overweight/obesity comorbid with ADHD may not be associated with cold executive functions, verbal short-term memory, learning, or ADHD symptom severity.