Intra-Individual Variability Among Children with ADHD on a Working Memory Task: An Ex-Gaussian Approach

Buzy, Wendy M.; Medoff, Deborah R.; Schweitzer, Julie B.

doi:10.1080/09297040802646991

Cited by 90 publications

(103 citation statements)

References 72 publications

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“…[6][7][8][9][10][11][12][13][14] Compared with reports on τ, reports on alterations of μ and σ in patients with ADHD have been less consistent, and findings seem more taskdependent. 10 The disorder has been associated with decreased μ, 7,9,12 increased σ, 7,9,[12][13][14] or no differences in μ 8,11,13,14 or σ. 8,11 These studies show that ADHD-related RTV is predominantly determined by extremely long RTs, which are best captured by an elevation in τ.…”

Section: Introductionmentioning

confidence: 66%

“…Several studies in children and adolescents have applied exGaussian analyses to RT data and have shown consistently that increased τ is associated with ADHD. [6][7][8][9][10][11][12][13][14] To our knowledge, the present study is the first of this size performed in adults that used ex-Gaussian analyses to demonstrate that these childhood findings may represent a persistent deficit in patients with ADHD. In addition, the correlation of τ with inattention symptoms supports earlier literature suggesting that excessively long RTs represent lapses of attention.…”

Section: Discussionmentioning

confidence: 99%

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Lower white matter microstructure in the superior longitudinal fasciculus is associated with increased response time variability in adults with attention-deficit/hyperactivity disorder

Wolfers

Onnink

Zwiers

et al. 2015

jpn

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IntroductionAttention-deficit/hyperactivity disorder (ADHD) is characterized by a pervasive pattern of age-inappropriate inattentive behaviour and/or impulsiveness and hyperactivity. Although ADHD is often viewed as a childhood disorder, it also affects 2.5% of adults, 1 which has profound negative implications for the patients themselves, their social environment and society. The pathophysiology of ADHD is still poorly understood owing in part to its substantial clinical and etiological heterogeneity. Increased response time variability (RTV) is one of the most common characteristics of patients with ADHD. Response time variability is the moment-to-moment fluctuation of performance in neuropsychological response time experiments and has been found to be increased in patients with ADHD across a number of different experimental paradigms, including sustained attention, flanker interference and working memory tasks (for reviews see the studies by Tamm and colleagues 3 and Kofler and colleagues 4 ). Recent studies suggest that increased performance variability in patients with ADHD might be a neurocognitive marker and may serve as a potential endophenotype for this disorder. 5,6 In addition to capturing RTV through standard deviation (SD) of response time (RT), other quantitative measures of RTV have also been reported. The exponentially modified Gaussian (ex-Gaussian) method, for example, provides quantification of the shapes of Background: Response time variability (RTV) is consistently increased in patients with attention-deficit/hyperactivity disorder (ADHD). A right-hemispheric frontoparietal attention network model has been implicated in these patients. The 3 main connecting fibre tracts in this network, the superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF) and the cingulum bundle (CB), show microstructural abnormalities in patients with ADHD. We hypothesized that the microstructural integrity of the 3 white matter tracts of this network are associated with ADHD and RTV. Methods: We examined RTV in adults with ADHD by modelling the reaction time distribution as an exponentially modified Gaussian (ex-Gaussian) function with the parameters μ, σ and τ, the latter of which has been attributed to lapses of attention. We assessed adults with ADHD and healthy controls using a sustained attention task. Diffusion tensor imaging-derived fractional anisotropy (FA) values were determined to quantify bilateral microstructural integrity of the tracts of interest. Results: We included 100 adults with ADHD and 96 controls in our study. Increased τ was associated with ADHD diagnosis and was linked to symptoms of inattention. An inverse correlation of τ with mean FA was seen in the right SLF of patients with ADHD, but no direct association between the mean FA of the 6 regions of interest with ADHD could be observed. Limitations: Regions of interest were defined a priori based on the attentional network model for ADHD and thus we might have missed effects in other networks. Conclusion: This stud...

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Section: Introductionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Lower white matter microstructure in the superior longitudinal fasciculus is associated with increased response time variability in adults with attention-deficit/hyperactivity disorder

Wolfers

Onnink

Zwiers

et al. 2015

jpn

View full text Add to dashboard Cite

show abstract

“…In particular, the authors reported a significant effect of WM load on ISV that was greater in ADHD compared to control participants when assessed using SDRT, but not for the CVRT; ex-Gaussian measures were not examined. Using ex-Gaussian measures, Buzy and colleagues (2009) found increases in tau in ADHD compared to TD participants during a WM task, but no increase in tau associated with increased working memory demands. In addition, Epstein and colleagues (2011) reported increased ISV (SDRT, CVRT and tau) in children with ADHD compared to TD controls across five different cognitive tasks that varied in their complexity and response requirements, although they did not report a differential effect of task for children with ADHD compared to TD children.…”

mentioning

confidence: 86%

“…For example, while deficient response control in children with ADHD has been demonstrated across a variety of cognitive tasks, there is inconsistent evidence as to how task characteristics, such as complexity, influence response control (Buzy et al 2009; Epstein et al 2011; Klein et al 2006; Vaurio et al 2009). In one of the first examinations of ISV across multiple cognitive tasks, Klein et al (2006) reported notable effect size differences between the ADHD and TD groups based on task complexity.…”

mentioning

confidence: 99%

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

Seymour

Mostofsky

Rosch

2015

J Abnorm Child Psychol

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Children with attention-deficit hyperactivity disorder (ADHD) consistently show impaired response control, including deficits in response inhibition and increased intrasubject variability (ISV) compared to typically-developing (TD) children. However, significantly less research has examined factors that may influence response control in individuals with ADHD, such as task or participant characteristics. The current study extends the literature by examining the impact of increasing cognitive demands on response control in a large sample of 81children with ADHD (40 girls) and 100 TD children (47 girls), ages 8–12 years. Participants completed a simple Go/No-Go (GNG) task with minimal cognitive demands, and a complex GNG task with increased cognitive load. Results showed that increasing cognitive load differentially impacted response control (commission error rate and tau, an ex-Gaussian measure of ISV) for girls, but not boys, with ADHD compared to same-sex TD children. Specifically, a sexually dimorphic pattern emerged such that boys with ADHD demonstrated higher commission error rate and tau on both the simple and complex GNG tasks as compared to TD boys, whereas girls with ADHD did not differ from TD girls on the simple GNG task, but showed higher commission error rate and tau on the complex GNG task. These findings suggest that task complexity influences response control in children with ADHD in a sexually dimorphic manner. The findings have substantive implications for the pathophysiology of ADHD in boys versus girls with ADHD.

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“…One of the more consistent findings in the ADHD neuropsychology literature is increased reaction time variability (RTV), also known as intra-individual variability, on computerized tasks [5]. Elevated RTV among individuals with ADHD compared with typically-developing children has been documented across multiple studies using a wide variety of computerized tasks, including those assessing working memory [6][7][8], attention [9], inhibitory control [8,[10][11][12][13], and choice discrimination [14]. These ADHD between-group differences on RTV tend to be larger in magnitude than most other neuropsychological indicators [15].…”

Section: Introductionmentioning

confidence: 96%

Reaction Time Variability in ADHD: A Review

et al. 2012

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For the past decade, intra-individual variability in reaction times on computerized tasks has become a central focus of cognitive research on Attention-Deficit/Hyperactivity Disorder (ADHD). Numerous studies document increased reaction time variability among children and adults with ADHD, relative to typically developing controls. However, direct comparisons with other disorders with heightened reaction time variability are virtually nonexistent, despite their potential to inform our understanding of the phenomenon. A growing literature examines the sensitivity of reaction time variability to theoretically and clinically relevant manipulations. There is strong evidence that stimulus treatment reduces reaction time variability during a range of cognitive tasks, but the literature is mixed regarding the impact of motivational incentives and variation in stimulus event rate. Most studies of reaction time variability implicitly assume that heightened reaction time variability reflects occasional lapses in attention, and the dominant neurophysiological interpretation suggests this variability is linked to intrusions of task-negative brain network activity during task performance. Work examining the behavioral and neurophysiological correlates of reaction time variability provides some support for these hypotheses, but considerably more work is needed in this area. Finally, because conclusions from each of domains reviewed are limited by the wide range of measures used to measure reaction time variability, this review highlights the need for increased attention to the cognitive and motivational context in which variability is assessed and recommends that future work always supplement macro-level variability indices with metrics that isolate particular components of reaction time variability.

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Intra-Individual Variability Among Children with ADHD on a Working Memory Task: An Ex-Gaussian Approach

Cited by 90 publications

References 72 publications

Lower white matter microstructure in the superior longitudinal fasciculus is associated with increased response time variability in adults with attention-deficit/hyperactivity disorder

Lower white matter microstructure in the superior longitudinal fasciculus is associated with increased response time variability in adults with attention-deficit/hyperactivity disorder

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

Reaction Time Variability in ADHD: A Review

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