Increased Intrasubject Variability in Boys with ADHD Across Tests of Motor and Cognitive Control

Abstract

Increased intrasubject variability (ISV), or short-term, within-person fluctuations in behavioral performance is consistently found in Attention-Deficit/Hyperactivity Disorder (ADHD). ADHD is also associated with impairments in motor control, particularly in boys. The results of the few studies that have examined variability in self-generated motor output in children with ADHD have been inconsistent. The current study examined variability in motor control during a finger sequencing task among boys with and without ADHD as well as the relationship between intrasubject variability during motor and cognitive control tasks. Changes in performance over the course of the task and associations with ADHD symptom domains were also examined to elucidate the nature of impaired motor control in children with ADHD. Fifty-one boys (ages 8 to 12 years) participated in the study, including 28 boys with ADHD and 23 typically developing (TD) boys. Participants completed a finger sequencing task and a Go/No-Go task providing multiple measures of response speed and variability. Boys with ADHD were slower and more variable in both intertap interval on the finger sequencing task and reaction time on the Go/No-Go task, with measures of speed and variability correlated across the two tasks. For the entire cohort, the only unique predictor of parent ratings of hyperactive-impulsive symptoms was variability in intertap interval during finger sequencing, whereas inattentive symptoms were only predicted by reaction time variability on the Go/No-Go task. These findings suggest that inefficient motor control is implicated in the pathophysiology of ADHD, particularly in regards to developmentally inappropriate levels of hyperactivity and impulsivity.

Cognitive Load Differentially Impacts Response Control in Girls and Boys with ADHD

“…Participants completed two computer-based GNG paradigms similar to the tasks described in previous studies: a simple GNG paradigm and a complex GNG paradigm (Mostofsky et al 2003; Shiels Rosch et al 2013; Vaurio et al 2009; Wodka et al 2007). …”

Motor overflow in children with attention-deficit/hyperactivity disorder is associated with decreased extent of neural activation in the motor cortex

“…The finger-sequencing task performed outside of the scanner was very similar to the one performed inside the scanner except that it consisted of 10 blocks (5 per hand) which included a ten second baseline, during which the participant remained still, followed by finger-sequencing until they completed ~45 individual finger taps as determined by the examiner (MacNeil et al, 2011; Shiels Rosch et al, 2013). Participants sat in a chair with a pillow on their lap, which served as a rest position for their non-tapping hand and were instructed to bend the elbow of their tapping hand.…”

“…It is well established that children with ADHD perform motor tasks more slowly (Denckla and Rudel, 1978), with more variability (Rubia et al, 1999; Shiels Rosch et al, 2013), and show greater motor overflow (Denckla and Rudel, 1978; Szatmari and Taylor, 1984; Mostofsky et al, 2003a) compared with typically developing children. Abnormal persistence of motor overflow movements is a notable and clinically relevant aspect of ADHD, reflecting an impaired ability to inhibit unintentional movement.…”

Reduced intrasubject variability with reinforcement in boys, but not girls, with ADHD: Associations with prefrontal anatomy

“…Participants completed a computer-based Go/No-Go (GNG) task (e.g., Shiels Rosch, Dirlikov, & Mostofsky, 2013). Task stimuli consisted of green spaceships for “go” trials and red spaceships for “no-go” trials (20% of trials) presented for 300 ms with an interstimulus interval of 2000 ms.…”

“…For responses to no-go stimuli (i.e., commission errors), participants lost 50 cents and feedback consisting of 3 purple frowning faces and 50 cents crossed out with a red “X”) was presented (Figure 1). Immediate feedback regarding the accuracy of the response and the amount of money earned or lost was intended to maximize the impact of the contingencies on task performance relative to the standard GNG, similar to previous studies in the literature (e.g., Bubnik et al, 2015; Shiels Rosch et al, 2013; Strand et al, 2012). This task was typically administered on the second day of testing.…”