Objective The purpose of the research study was to examine the manifestation of variability in reaction times (RT) in children with Attention Deficit Hyperactivity Disorder (ADHD) and to examine whether RT variability presented differently across a variety of neuropsychological tasks, was present across the two most common ADHD subtypes, and whether it was affected by reward and event rate (ER) manipulations. Method Children with ADHD-Combined Type (n=51), ADHD-Predominantly Inattentive Type (n=53) and 47 controls completed five neuropsychological tasks (Choice Discrimination Task, Child Attentional Network Task, Go/No-Go task, Stop Signal Task, and N-back task), each allowing trial-by-trial assessment of reaction times. Multiple indicators of RT variability including RT standard deviation, coefficient of variation and ex-Gaussian tau were used. Results Children with ADHD demonstrated greater RT variability than controls across all five tasks as measured by the ex-Gaussian indicator tau. There were minimal differences in RT variability across the ADHD subtypes. Children with ADHD also had poorer task accuracy than controls across all tasks except the Choice Discrimination task. Although ER and reward manipulations did affect children’s RT variability and task accuracy, these manipulations largely did not differentially affect children with ADHD compared to controls. RT variability and task accuracy were highly correlated across tasks. Removing variance attributable to RT variability from task accuracy did not appreciably affect between-group differences in task accuracy. Conclusions High RT variability is a ubiquitous and robust phenomenon in children with ADHD.

Abstract— The sodium‐dependent high affinity choline uptake into synaptosomes from rat brain has been studied after in vivo treatments which would alter the activity of cholinergic neurons. We utilized a number of treatments to reduce the activity of cholinergc neurons in the brain. Administration of pentobarbital (65 mg/kg), chloral hydrate (40 mg/kg) and γbutyrelactone (750 mg/kg) caused a 50‐80% reduction in sodium‐dependent high affinity choline uptake in several brain regions (30 min). This depression was not found 24 h after injection. Interruption of the cholinergic septal‐hippocampal or habenuleinterpeduncular tracts by lesions (10 min‐1 h) also caused a similar, large reduction in sodium‐dependent high affinity choline uptake in the hippocampus and the interpeduncular nucleus respectively. We reversed the inactivity after pentobarbital administration by direct electrical stimulation of the cholinergic septal‐hippocampal tract. Stimulation (40 Hz) for 10‐15 min completely reversed the depression in sodium‐dependent high affinity choline uptake. Stimulation at lower frequencies or for shorter times caused a partial reversal. Administration of pentylenetetrazol (75 mg/kg), a convulsant, was utilized to increase the activity of central cholinergic neurons. After drug administration, we found a large (60%) increase in sodium‐de‐pendent high affinity choline uptake. This increase was not found in the hippocampus when cholinergic afferents were interrupted by septal lesion prior to drug administration. We also examined the uptake after administration of cholinergic drugs. Oxotremorine (0.75 mg/kg), a muscarinic agonist which reduces acetylcholine release and turnover, caused a reduction in uptake. On the other hand, administration of scopolamine (5 mg/kg), a cholinergic antagonist which increases acetylcholine turnover, caused an increase in sodium‐dependent high affinity choline uptake. Addition of any drug utilized, drectly to uptake samples, did not alter uptake. We examined the conversion of [3H]choline to [3H]acetylcholine in hippocampal synaptosomes after septal lesion, pentylenetetrazol administration and in untreated controls. In all cases, 60‐70% of the total sodium‐dependent tritium content was present as [3H]acetylcholine. Evidence was presented that homoexchange is not or is less involved in choline uptake than in GABA uptake. A kinetic analysis of sodium‐dependent high affinity choline uptake was performed after all treatments. We found changes in Vmax, after all treatments, which were consistently in the same direction as the alterations in activity. The proposal is made that the sodium‐dependent high affinity choline uptake is coupled to cholinergic activity in such a way as to regulate the entry of choline for the maintenance of acetylcholine synthesis. The findings also lead us to propose that sodium‐dependent high affinity choline uptake in vitro be utilized as a rapid, relative measure of the activity of cholinergic nerve terminals in vivo.

The high affinity uptake systems for iron and copper ions in Saccharomyces cerevisiae involve metal-specific permeases and two known cell surface Cu(II) and Fe (

Parent-teacher agreement on Attention Deficit/Hyperactivity Disorder (ADHD) symptom ratings range from low to moderate. Most studies evaluating parent-teacher agreement have not assessed measurement invariance across raters. Hence, it is unclear whether discordance across raters is due to differing ADHD constructs across raters or other factors (e.g., subjective differences across raters). Additionally, the effect of development on parent-teacher agreement is relatively unknown. To address these limitations, the present study utilized parent and teacher ADHD ratings from a large (N=6,659), developmentally diverse (ages 4–17) sample. Exploratory structural equation modeling using half the sample and then Confirmatory Factor Analysis (CFA) on the second half of the sample identified a two-factor structure for the 18 ADHD symptoms. CFA invariance analyses demonstrated that the two factor symptom structure was similar across raters and age groups. Also, parents reported greater severity of ADHD symptoms than teachers and both parents and teachers report higher levels of HI in younger children than older children and consistent levels of inattention across development. Finally, correlations between parent-teacher ratings of like-factor ratings were weak for Inattention (IA) and moderate-strong for Hyperactivity/Impulsivity (HI) and that the magnitude of parent-teacher agreement did not vary across development. In conclusion, while parent and teacher ratings of ADHD behaviors are only weakly to moderately correlated, each reporter provides unique and valid clinical information as it relates to ADHD symptom presentation.