Increased intra-individual reaction time variability in attention-deficit/hyperactivity disorder across response inhibition tasks with different cognitive demands

Abstract

One of the most consistent findings in children with ADHD is increased moment-to-moment variability in reaction time (RT). The source of increased RT variability can be examined using ex-Gaussian analyses that divide variability into normal and exponential components and Fast Fourier transform (FFT) that allow for detailed examination of the frequency of responses in the exponential distribution. Prior studies of ADHD using these methods have produced variable results, potentially related to differences in task demand. The present study sought to examine the profile of RT variability in ADHD using two Go/No-go tasks with differing levels of cognitive demand. A total of 140 children (57 with ADHD and 83 typically developing controls), ages 8–13 years, completed both a “simple” Go/No-go task and a more “complex” Go/No-go task with increased working memory load. Repeated measures ANOVA of ex-Gaussian functions revealed for both tasks children with ADHD demonstrated increased variability in both the normal/Gaussian (significantly elevated sigma) and the exponential (significantly elevated tau) components. In contrast, FFT analysis of the exponential component revealed a significant task × diagnosis interaction, such that infrequent slow responses in ADHD differed depending on task demand (i.e., for the simple task, increased power in the 0.027–0.074 Hz frequency band; for the complex task, decreased power in the 0.074–0.202 Hz band). The ex-Gaussian findings revealing increased variability in both the normal (sigma) and exponential (tau) components for the ADHD group, suggest that both impaired response preparation and infrequent “lapses in attention” contribute to increased variability in ADHD. FFT analyses reveal that the periodicity of intermittent lapses of attention in ADHD varies with task demand. The findings provide further support for intra-individual variability as a candidate intermediate endophenotype of ADHD.

Altered spontaneous low frequency brain activity in Attention Deficit/Hyperactivity Disorder

“…Recent research by the same group (Di Martino et al, 2008) as well as others (e.g. Johnson et al, 2007;Vaurio et al, 2009) have also found a predictable pattern of increased power in VLF RTV (<0.1 Hz) in children with ADHD. In contrast, Geurts et al (2008) did not find any evidence for increased RTV in children with ADHD in terms of oscillatory power after applying spectral analysis, ex-Gaussian techniques and intra-individual variability analysis.…”

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

“…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.…”

“…[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.…”

Sustaining visual attention in the face of distraction: a novel gradual-onset continuous performance task

“…Second, intraindividual variability in RTs has been linked to impairments of attention and executive function (e.g., attention-deficit hyperactivity disorder, ADHD), such that more erratic responding is related to greater deficits (SonugaBarke & Castellanos, 2007;Stuss, Murphy, Binns, & Alexander, 2003;West, Murphy, Armilio, Craik, & Stuss, 2002). For example, even when overall speed is controlled, those with ADHD show more variable correct responses and more prominent RT fluctuations every 12-40 s (Castellanos, Sonuga-Barke, Milham, & Tannock, 2006;Di Martino et al, 2008;Vaurio, Simmonds, & Mostofsky, 2009). Important to the goals of the present study, previous work has yet to explore changes in within-subjects response variability as attention fluctuates over time (for one exception, see Faulkner, 1962).…”