Effects of Motivation and Medication on Electrophysiological Markers of Response Inhibition in Children with Attention-Deficit/Hyperactivity Disorder

Abstract

BackgroundTheories of attention-deficit/hyperactivity disorder (ADHD) posit either executive deficits and/or alterations in motivational style and reward processing as core to the disorder. Effects of motivational incentives on electrophysiological correlates of inhibitory control and relationships between motivation and stimulant medication have not been explicitly tested.MethodsChildren (9–15 years) with combined-type ADHD (n = 28) and matched typically developing children (CTRL) (n = 28) performed a go/no-go task. Electroencephalogram data were recorded. Amplitude of two event-related potentials, the N2 and P3 (markers of response conflict and attention), were measured. The ADHD children were all stimulant responders tested on and off their usual dose of methylphenidate; CTRLs were never medicated. All children performed the task under three motivational conditions: reward; response cost; and baseline, in which points awarded/deducted for inhibitory performance varied.ResultsThere were effects of diagnosis (CTRL > ADHD unmedicated), medication (on > off), and motivation (reward and/or response cost > baseline) on N2 and P3 amplitude, although the N2 diagnosis effect did not reach statistical significance (p = .1). Interactions between motivation and diagnosis/medication were nonsignificant (p > .1).ConclusionsMotivational incentives increased amplitudes of electrophysiological correlates of response conflict and attention in children with ADHD, towards the baseline (low motivation) amplitudes of control subjects. These results suggest that, on these measures, motivational incentives have similar effects in children with ADHD as typically developing CTRLs and have additive effects with stimulant medication, enhancing stimulus salience and allocation of attentional resources during response inhibition.

Ten years on: A follow-up review of ERP research in attention-deficit/hyperactivity disorder

“…Liotti et al (2009) presented a similar conclusion, with their results indicating deficient cognitive monitoring operations, rather than a simple account in terms of inhibitory control. Groom et al (2010b) identified the important role of motivational factors, providing some support for the model proposed by Sonuga-Barke (2002). There is also ERP evidence for a developmental lag in inhibition but not attention processes (Doehnert et al, 2010), in line with EEG findings which characterise AD/HD in terms of a maturational lag (see Barry et al, 2003a).…”

“…However, many instances of less than ideal age-ranges can also be identified, with children and young adolescents grouped together (e.g. Johnstone et al, 2007a;Groom et al, 2010b), or broad ranges with age not used as a grouping factor in the analysis (e.g. Williams et al, 2008).…”

“…Groom et al (2008) reported that adolescents with AD/HDcom showed reduced N2 in a Go/Nogo but not Oddball task, and no P3 differences in either task, suggesting persistence of inhibition deficits into adolescence. Groom et al (2010b) examined the influence of motivation on Go/Nogo task performance, and reported that N2 and P3 were larger when the incentive to inhibit was increased for all participants, and children with AD/HDcom showed reduced P3 (indicating decreased attention) to the task relevant stimuli regardless of incentives (Groom et al, 2010b).…”

Differential modulation of the N2 and P3 event-related potentials by response conflict and inhibition

“…Studies using go/no-go and stop signal tasks 7 have often reported high rates of inhibitory errors coupled with reduced N2 amplitude (Barry, Johnstone, & Clarke, 2003;Brandeis et al, 1998;Groom et al, 2010;Liotti, Pliszka, Perez, Kothmann, & Woldorff, 2005) interpreted as poor inhibitory control. However, as outlined above, response inhibition paradigms may reflect conflict between competing responses as well as (or instead of) the cancellation of a planned or prepotent response.…”

“…Impaired cognitive control has been reported in a range of neurodevelopmental disorders, particularly attention deficit/hyperactivity disorder (ADHD) (Groom et al, 2008;Groom et al, 2010;Pliszka, Liotti, & Woldorff, 2000;Yong-Liang et al, 2000) and schizophrenia (Groom et al, 2008;Kiehl, Smith, Hare, & Liddle, 2000;Roche et al, 2004). However the precise features of cognitive control that are impaired have not been well characterised, partly because of a lack of consistency in how these processes are measured and described.…”