Time Course Analysis of Motor Excitability in a Response Inhibition Task According to the Level of Hyperactivity and Impulsivity in Children with ADHD

Abstract

Short interval intracortical inhibition (SICI) of motor cortex, measured by transcranial magnetic stimulation (TMS) in a passive (resting) condition, has been suggested as a neurophysiological marker of hyperactivity in attention-deficit/hyperactivity disorder (ADHD). The aim of this study was to determine motor excitability in a go/nogo task at stages of response preparation, activation and suppression in children with ADHD, depending on the level of hyperactivity and impulsivity. Motor evoked potentials were recorded in 29 typically developing children and 43 children with ADHD (subdivided in two groups with higher and lower levels of hyperactivity/impulsivity; H/I-high and H/I-low). In the H/I-high group, SICI was markedly reduced in the resting condition and during response preparation. Though these children were able to increase SICI when inhibiting a response, SICI was still reduced compared to typically developing children. Interestingly, SICI at rest and during response activation were comparable, which may be associated with their hypermotoric behaviour. In the H/I-low group, response activation was accompanied by a pronounced decrease of SICI, indicating reduced motor control in the context of a fast motor response. In summary, different excitability patterns were obtained for the three groups allowing a better understanding of dysfunctional response activation and inhibition processes within the motor cortex in children with ADHD.

Effects of prenatal alcohol consumption on cognitive development and ADHD‐related behaviour in primary‐school age: a multilevel study based on meconium ethyl glucuronide

“…In the second and third task block, a monetary reward (10 cents per trial) was given for fast responses in go‐trials to increase motivation. The time window, for which fast responses were rewarded, was based on a tracking algorithm and was dynamically adjusted to the 75th percentile of reaction times (go‐trials) of the previous block (Hoegl et al., ). The same amount of money was subtracted in the case of an incorrect reaction (reaction to a nogo trial or no reaction to a go‐stimulus).…”

Reduced Short Interval Cortical Inhibition Correlates With Atomoxetine Response in Children With Attention-Deficit Hyperactivity Disorder (ADHD)

“…SICI was selected as a primary candidate based on case-control studies showing reduced SICI in ADHD and correlations between less SICI and greater ADHD symptom severity. 7,10,16,20 Moreover, in prior studies, SICI did appear to be sensitive to single doses of psychostimulants and of norepinephrine reuptake inhibitors reboxetine and ATX. 6,8,16,31 Most single dose studies have recruited small samples of healthy adults or children.…”

Online Transcranial Magnetic Stimulation Protocol for Measuring Cortical Physiology Associated with Response Inhibition

“…Some groups have successfully used TMS during GNG task to show differences in cortical physiology in children and adults. 14,23,34 However, GNG task should ideally be conducted at a relatively fast pace to elicit prepotent motor response throughout the task so that inhibitory control can be adequately examined in Nogo trials. 35,36 From methodological standpoint, a fast-paced GNG task imposes difficulties for online fTMS experiments as device capacitors require time to recharge for the next stimulation pulse.…”

“…Furthermore, one study showed that a single dose of methylphenidate changed motor cortical physiology of healthy adults during an fTMS/GNG experiment. 22 To date, there are two groups that have published pediatric fTMS studies using GNG task to characterize cortical physiology of ADHD 23 and Tourette Syndrome 17 . There is currently no published fTMS study utilizing SST in the pediatric population.…”