Context-dependent Dynamic Processes in Attention Deficit/Hyperactivity Disorder: Differentiating Common and Unique Effects of State Regulation Deficits and Delay Aversion

Abstract

The ability to specify differential predictions is a mark of a scientific models' value. State regulation deficits (SRD) and delay aversion (DAv) have both been hypothesized as context-dependent dynamic dysfunctions in ADHD.However, to date there has been no systematic comparison of their common and unique elements. Here we review these hypotheses -and describe the core and secondary manifestations of the two constructs and review evidenceIn support of them. Second, we focus on what are seen as the hallmark indicators of the two deficits -preference of small immediate over large delayed rewards for DAv and the slow event rate effect for SRD. We describe the overlap between these two manifestations and then explore how experimental manipulations and the analysis of neuropsychological and physiological mediators of effects can allow us to differentiate these two patterns of neuropsychological dysfunction on the basis of specific predictions. Finally, we highlight the implications of neuropsychological heterogeneity for the practical implementation of tests of DAv and SRD.Key words: Attention Deficit/Hyperactivity Disorder; delay aversion; state regulation; cognitive energetic; event rate; delay of gratification; delayed reward. 4 MOVING BEYOND FIXED DEFICIT MODELS OF ADHDAttention Deficit/Hyperactivity Disorder (ADHD) is a prevalent child and adolescent condition, which often persists into adulthood, marked by developmentally inappropriate and pervasive expressions of inattention, overactivity and impulsiveness (Banaschewski et al., in press). It is associated with functional impairments across multiple academic and social domains and is commonly accompanied by a range of externalising (e.g., conduct disorder) and internalising (e.g., anxiety) comorbid disorders (Taylor and SonugaBarke, 2008). Until recent times dominant neuropsychological theories of ADHD have focused on cognitive impairments associated with deficits in executive functions such as inhibitory control (Nigg, 2005) and working memory (Rapport et al., 2008). These are postulated to be grounded in altered fronto-striatal neural circuits modulated by catecholamine-based neuro-transmitters (Arnsten, 2009). Support for executive impairments in ADHD of the sort predicted by these models come from many studies (e.g. Willcutt et al., 2005;Bitsakou et al., 2008). However, it now seems unlikely that such deficits mediate the link between ADHD and its underlying causes (i.e., genes and environments; in any straightforward way . For instance, many children with ADHD appear not to have dysfunctional executive processes, while many children without ADHD, either with others disorders or with no disorder at all, do (Willcutt et al., 2005). Even where ADHD and executive dysfunction co-present the pattern is 5 rather fragmented and variable so that pervasive and severe executive deficit appears quite rare . Perhaps reflecting the influence of the classical bio-medical framework (Singh, 2008) and neuropsychological models of brain insult (Loge et al., 1990), ...

Event-rate effects in the flanker task: ERPs and task performance in children with and without AD/HD

“…However, it was found that the control group made more errors at the slow than medium event-rate, whereas the AD/HD group made more errors at the medium than slow eventrate. This result is surprising considering performance deficits in AD/HD most commonly occur to slow event-rates (Sonuga-Barke et al, 2010;Wiersema et al, 2006b). However, as energetic state is both idiosyncratic and task-dependent, the findings of the present study may be attributable to the unique task requirements of the flanker task (Sonuga-Barke et al, 2010).…”

“…This result is surprising considering performance deficits in AD/HD most commonly occur to slow event-rates (Sonuga-Barke et al, 2010;Wiersema et al, 2006b). However, as energetic state is both idiosyncratic and task-dependent, the findings of the present study may be attributable to the unique task requirements of the flanker task (Sonuga-Barke et al, 2010). Conversely, as mentioned previously, a larger interference effect (incongruent>neutral) was found for omission errors in the AD/HD compared to the control group.…”

“…Event-rate (i.e., the speed at which stimuli are presented) varies the rate at which motor responses are required, making it an appropriate manipulation of energetic state (Sanders, 1983). Compared to a medium event-rate, a fast event-rate is thought to induce over-arousal and fast inaccurate responding, and a slow event-rate is thought to induce under-arousal and slow inaccurate responding (Sergeant, 2000;Sonuga-Barke et al, 2010). Thus, the CEM predicts that the effect of arousal-level on task performance should follow a U-shaped pattern.…”

A Meta-Analytic Study of Event Rate Effects on Go/No-Go Performance in Attention-Deficit/Hyperactivity Disorder

“…Second, there is accumulating evidence for the context-dependent nature of deficits when they do occur -performance of an individual subject may vary from setting to setting as a function of the motivational and energetic state that they engender (5). For instance, performance on a wide range of cognitive tasks is affected in non-specific ways by the rate at which stimuli are presented (i.e., event rate (ER)), which is determined by inter-stimulus interval (ISI) (6,7).…”

“…These ER effects have been observed on tasks of different sorts including go/no-go (8), stop signal (9) vigilance (10) and associative learning (11) tasks. Such task nonspecific ER effects have been explained in different ways (5). The most often invoked explanation is based on the cognitive energetic model of Sanders (12).…”