Relationship between reaction time variability and motor skill development in ADHD

Slower and more variable reaction times to computerized tasks have been documented in children diagnosed with attention deficit/hyperactivity disorder (ADHD). Recent research supports a role for attentional lapses in generating abnormally variable and slow responses. However, given the association between ADHD and impairments in motor control, we hypothesized that slower or more variable reaction times might also correlate with motor development. The aim of this case-control study was to explore the relationship between motor function, reaction speed and variability, and ADHD. After comprehensive educational and clinical assessments, motor skill development was evaluated in 35 children ages 9 to 14 (19 with ADHD) using the Physical and Neurological Examination for Subtle Signs (PANESS) test battery. Finger-sequencing speed and variability were quantified with goniometers. Reaction times were measured with 20 trials each of computerized simple and choice (binary) tasks. Compared to healthy controls, children with ADHD had slower and more variable reaction times, and these findings correlated with impaired motor development (PANESS) and slow and variable finger sequencing (goniometers). Further studies of motor development in ADHD may identify factors influencing speed and variability of reaction times.     

Working memory and behavioral inhibition in children with attention-deficit/hyperactivity disorder (ADHD): an examination of varied central executive demands,construct overlap,and task impurity

The stop-signal paradigm is the premier metric of behavioral inhibition in contemporary attention-deficit/hyperactivity disorder (ADHD) research. The stop-signal paradigm’s choice-reaction time component, however, arguably places greater demands on working memory processes (e.g., controlled-focused attention) relative to alternative inhibition metrics (i.e., go/no-go (GNG) tasks), and consequently obscures conclusions about inhibition and working memory deficits in affected children. The current study, therefore, aimed to determine whether shared variance between stop-signal behavioral inhibition and working memory performance in children with ADHD reflects overlap between the working memory and inhibition constructs or insufficient specificity of the stop-signal paradigm. Fifty-five children (8–12 years) with and without ADHD were administered established phonological (PH) and visuospatial (VS) working memory measures, as well as stop-signal and GNG tasks that vary with respect to demands on controlled-focused attention. Although working memory and GNG performance each uniquely predicted children’s inattention, stop-signal task performance was not a significant predictor of unique variance in inattention, above and beyond variance associated with working memory. Collectively, these findings suggest that performance on the stop-signal task, compared to the GNG task, is confounded by greater demands associated with working memory and consequently reflects an impure estimate of the inhibition construct.     

Teachers' and education students' perceptions of and reactions to children with and without the diagnostic label "ADHD"

Thirty-four elementary school teachers and 32 education students from Canada rated their reactions towards vignettes describing children who met attention-deficit/hyperactivity disorder (ADHD) symptom criteria that included or did not include the label “ADHD.” “ADHD”-labeled vignettes elicited greater perceptions of the child's impairment as well as more negative emotions and less confidence in the participants, although it also increased participants' willingness to implement treatment interventions. Ratings were similar to vignettes of boys versus girls; however, important differences in ratings between teachers and education students emerged and are discussed. Finally, we investigated the degree to which teachers' professional backgrounds influenced bias based on the label “ADHD.” Training specific to ADHD consistently predicted label bias, whereas teachers' experience working with children with ADHD did not.     

Working Memory Deficits in Boys with Attention-deficit/Hyperactivity Disorder (ADHD): The Contribution of Central Executive and Subsystem Processes

The current study investigated contradictory findings from recent experimental and meta-analytic studies concerning working memory deficits in ADHD. Working memory refers to the cognitive ability to temporarily store and mentally manipulate limited amounts of information for use in guiding behavior. Phonological (verbal) and visuospatial (nonverbal) working memory were assessed across four memory load conditions in 23 boys (12 ADHD, 11 typically developing) using tasks based on Baddeley's (Working memory, thought, and action, Oxford University Press, New York, 2007) working memory model. The model posits separate phonological and visuospatial storage and rehearsal components that are controlled by a single attentional controller (CE: central executive). A latent variable approach was used to partial task performance related to three variables of interest: phonological buffer/rehearsal loop, visuospatial buffer/rehearsal loop, and the CE attentional controller. ADHD-related working memory deficits were apparent across all three cognitive systems--with the largest magnitude of deficits apparent in the CE--even after controlling for reading speed, nonverbal visual encoding, age, IQ, and SES.     

Experiences of physical and relational victimization in children with ADHD: The role of social problems and aggression

The social risk factors for physical and relational peer victimization were examined within a mixed‐gender sample of children with and without attention‐deficit/hyperactivity disorder (ADHD). Participants were 124 children (ages 8–12 years; 48% boys), with 47% exhibiting sub‐clinical or clinical elevations in ADHD symptoms. ADHD and oppositional defiant disorder (ODD) symptom counts were assessed based on parent‐ and teacher‐reports; parents rated children's social problems and teachers rated children's use of physical and relational aggression and experiences of physical and relational victimization. A multiple mediator model was used to test whether there were indirect effects of ADHD or ODD symptoms on physical and relational victimization through social problems, physical aggression, or relational aggression. At the bivariate level, ADHD and ODD symptoms were both significantly associated with higher rates of physical and relational victimization. In the mediational model, there were significant indirect effects of ADHD symptoms on relational victimization via social problems, of ODD on relational victimization via relational aggression, and of ODD symptoms on physical victimization via physical aggression. Results suggest that there are distinct risk factors implicated in the physical and relational victimization of youth with ADHD and that the co‐occurrence of ODD symptoms is important to assess. Clinical implications for addressing victimization in children with ADHD are discussed.

     

Written expression in boys with ADHD: The mediating roles of working memory and oral expression

The written expression difficulties experienced by children with ADHD are widely recognized; however, scant empirical evidence exists concerning the cognitive mechanisms and processes underlying these deficiencies. The current study investigated the independent and potentially interactive contributions of two developmentally antecedent cognitive processes – viz., working memory (WM) and oral expression – hypothesized to influence written expression ability in boys. Thirty-three boys with ADHD-Combined Presentation and 27 neurotypical (NT) boys 8–12 years of age were administered standardized measures of oral and written expression, and multiple counterbalanced tasks to assess WM central executive (CE) processes, WM phonological short-term memory (PH STM), and WM visuospatial short-term memory (VS STM). Bias-corrected bootstrapped mediation analyses revealed a significant mediation effect, wherein the independent and interactive effects of PH STM and oral expression collectively explained 76% of the diagnostic status to written expression relation. The implications of the obtained results for clinical practice suggest that children with ADHD may benefit by incorporating a blended approach that simultaneously strengthens PH STM capacity and oral expression abilities as antecedents to engaging in writing-related activities.     

Neurocognitive performance of 5- and 6-year-old children who met criteria for attention deficit/hyperactivity disorder at 18 months follow-up: results from a prospective population study

The aim of this prospective study was to examine whether neurocognitive performance of children aged 5–6 years distinguished children who were later diagnosed with attention deficit/hyperactivity disorder (ADHD) or borderline ADHD from children without ADHD after adjustment for behavioral measures and to examine the influence of comorbid psychopathology. Out of a general population of 1,317 children, 366 children were selected on the basis of their scores on the Child Behavior Checklist (CBCL). Eighteen months later, the parents were interviewed using a standardized child psychiatric interview: 33 children were classified as ADHD and 75 children as borderline ADHD, and there were 258 children without ADHD. Children with rated ADHD were significantly impaired on measures of visuomotor ability and working memory compared to children without ADHD after adjustment for CBCL results. The performance of borderline ADHD children was in between that of children with and without ADHD. In addition, 4 groups of children were analyzed: 9 ADHD, 24 ADHD with comorbid oppositional defiant disorder/conduct disorder (ODD/CD), 59 ODD/CD, and 274 controls. Children with rated comorbid ADHD and ODD/CD performed significantly worse on these tasks compared to children with rated ODD/CD and control children while they did not differ from ADHD children. Our results imply that neurocognitive measures can contribute to the early identification of ADHD with and without comorbid ODD/CD.     

Effects of methylphenidate on sensitivity to reinforcement in children diagnosed with attention deficit hyperactivity disorder: an application of the matching law

The behavior of children diagnosed with attention deficit hyperactivity disorder (ADHD) has been hypothesized to be the result of decreased sensitivity to consequences compared to typical children. The present study examined sensitivity to reinforcement in 2 boys diagnosed with ADHD using the matching law to provide more precise and quantitative measurement of this construct. This experiment also evaluated the effects of methylphenidate (MPH) on sensitivity to reinforcement of children with ADHD. Subjects completed math problems to earn tokens under four different variable-interval (VI) schedules of reinforcement presented in random order under both medicated and nonmedicated conditions. Results showed that, in the medicated condition, the matching functions for both subjects resulted in higher asymptotic values, indicating an overall elevation of behavior rate under these conditions. The variance accounted for by the matching law was also higher under the medicated conditions, suggesting that their behavior more closely tracked the changing rates of reinforcement while taking MPH compared to placebo. Under medicated conditions, the reinforcing efficacy of response-contingent tokens decreased. Results are discussed with respect to quantifying behavioral changes and the extent to which the drug interacts with prevailing contingencies (i.e., schedule values) to influence behavioral variability.     

Stimulant Treatment Reduces Lapses in Attention among Children with ADHD: The Effects of Methylphenidate on Intra-Individual Response Time Distributions

Recent research has suggested that intra-individual variability in reaction time (RT) distributions of children with ADHD is characterized by a particularly large rightward skew that may reflect lapses in attention. The purpose of the study was to provide the first randomized, placebo-controlled test of the effects of the stimulant methylphenidate (MPH) on this tail and other RT distribution characteristics. Participants were 49 9- to 12-year-old children with ADHD. Children participated in a 3-day double-blind, placebo-controlled medication assessment during which they received long-acting MPH (Concerta®), with the nearest equivalents of 0.3 and 0.6 mg/kg t.i.d. immediate-release MPH. Children completed a simple two-choice speeded discrimination task on and off of medication. Mode RT and deviation from the mode were used to examine the peak and skew, respectively, of RT distributions. MPH significantly reduced the peak and skew of RT distributions. Importantly, the two medication effects were uncorrelated suggesting that MPH works to improve both the speed and variability in responding. The improvement in variability with stimulant treatment is interpreted as a reduction in lapses in attention. This, in turn, may reflect stimulant enhancement of self-regulatory processes theorized to be at the core of ADHD.     

Motor timing deficits in community and clinical boys with hyperactive behavior: the effect of methylphenidate on motor timing

In a previous paper we showed that community children with hyperactive behavior were more inconsistent than controls in the temporal organization of their motor output. In this study we investigated: (1) various aspects of motor timing processes in 13 clinically diagnosed boys with attention deficit hyperactivity disorder (ADHD) who were compared to 11 community boys with hyperactive behavior and to a control group and (2) the effect of methylphenidate on the motor timing processes in the clinical group with ADHD in a double blind, cross-over, medication-placebo design, including 4 weeks of medication. The clinical group with ADHD, like the community group with hyperactivity, showed greater variability in sensorimotor synchronization and in sensorimotor anticipation relative to controls. The clinical group was also impaired in time perception, which was spared in the community group with hyperactivity. The persistent, but not the acute dose, of methylphenidate reduced the variability of sensorimotor synchronization and anticipation, but had no effect on time perception. This study shows that motor timing functions are impaired in both clinical and community children with hyperactivity. It is the first study to show the effectiveness of persistent administration of methylphenidate on deficits in motor timing in ADHD children and extends the use of methylphenidate from the domain of attentional and inhibitory functions to the domain of executive motor timing.     

Multiple family therapy for Chinese families of children with attention deficit hyperactivity disorder (ADHD): treatment efficacy from the children’s perspective and their subjective experiences

This paper reports the results of our study that assessed the treatment efficacy of multiple family therapy (MFT) from the perspective of participating Chinese children with attention deficit hyperactivity disorder (ADHD) and identified their subjective experiences. Forty‐three children with ADHD in the experimental group (EG) completed a forty‐two‐hour MFT, whilst forty‐five children with ADHD in the control group (CG) had attended two writing classes scheduled three months apart that were similar to those of the MFT. Data from the outcome study were gathered using standardized questionnaires and data from the qualitative study were drawn from thirteen children with ADHD who had completed the MFT and attended the focus group interviews (n = 5) or individual interviews (n = 8) conducted in the post‐treatment phase. The results of the Paired sample t‐test and MANOVA indicated no significant changes on the scores for the four measures adopted (perception of competence, hopefulness, parent‐child relationship and perceived social support) in the pre‐ and post‐treatment for the EG and the CG. Five themes emerged from the narratives of children with ADHD, which revealed the children’s subjective experiences with the MFT: (a) full of fun; (b) building friendships through common experiences; (c) a happy family time; (d) safe space; and (e) positive parental responses and communications.