Living in the Fast Lane: Evidence for a Global Perceptual Timing Deficit in Childhood ADHD Caused by Distinct but Partially Overlapping Task-Dependent Cognitive Mechanisms

Abstract

Dysfunctions in perceptual timing have been reported in children with ADHD, but so far only from studies that have not used the whole set of timing paradigms available from the literature, with the diversity of findings complicating the development of a unified model of timing dysfunctions and its determinants in ADHD. Therefore, we employed a comprehensive set of paradigms (time discrimination, time estimation, time production, and time reproduction) in order to explore the perceptual timing deficit profile in our ADHD sample. Moreover, we aimed to detect predictors responsible for timing task performance deficits in children with ADHD and how the timing deficits might be positively affected by methylphenidate. Male children with ADHD and healthy control children, all aged between 8 and 13 years, participated in this longitudinal study with three experimental sessions, where children with ADHD were medicated with methylphenidate at the second session but discontinued their medication at the remaining sessions. The results of our study reveal that children with ADHD were impaired in all timing tasks, arguing for a general perceptual timing deficit in ADHD. In doing so, our predictor analyses support the notion that distinct but partially overlapping cognitive mechanisms might exist for discriminating, estimating/producing, and reproducing time intervals. In this sense, working memory deficits in terms of an abnormally fast internal counting process might be common to dysfunctions in the time estimation/time production tasks and in the time reproduction task, with attention deficits (e.g., in terms of disruptions of the counting process) additionally contributing to time estimation/time production deficits and motivational alterations additionally contributing to time reproduction deficits. Methylphenidate did not significantly alter performance of the ADHD sample, presumably due to limited statistical power of our study. The findings of our study demonstrate a pivotal role of disturbed working memory processes in perceptual timing task performance in childhood ADHD, at the same time broadening the view for additional attentional and motivational determinants of impaired task performance.

Deficits in Visuo-Motor Temporal Integration Impacts Manual Dexterity in Probable Developmental Coordination Disorder

“…The attention-deficit hypothesis has been discussed in the context of ADHD ( 120 ). The timing deficit hypothesis, which has been mainly verified as the etiology of ADHD ( 121 ), has also been suggested to underlie DCD ( 122 ). However, several studies investigating the automatization deficit of DCD also reported negative results ( 16 , 123 – 127 ).…”

Perceptual timing in children with attention-deficit/hyperactivity disorder (ADHD) as measured by computer-based experiments versus real-life tasks: protocol for a cross-sectional experimental study in an ambulatory setting

“…In this sense, WM should be crucial only for timing performance from about 1 s and longer, when temporal characteristics of the experimental stimuli have to be analysed and information has to be held in mind until the comparison stimulus is displayed. Beyond WM, time discrimination performance in children and adolescents with ADHD was associated with measures of attention and impulsivity, but only in studies using longer stimulus presentation durations5 14 and longer ISI 17. In addition, we suggested delay aversion and its secondary adaptations, that is, the motivational tendency to escape from delay by investing less time in a task if this helps to reduce overall experimental duration,18 as a further potential predictor of disturbed timing processes in ADHD.…”

“…The latter, in contrast, require additional cognitive resources, as they ask the child to provide a verbal duration estimation of a previously presented stimulus (time estimation), to produce a previously specified time interval, for example, by pressing a response button (time production), or to infer the duration of a stimulus that had been previously presented for a defined time interval and to indicate this time interval subsequently by pressing a response button (time reproduction). Based on our experimental findings using these four paradigms,5 we recently proposed a model of disturbed perceptual timing in children with ADHD, consisting of two distinct but partially overlapping neurocognitive mechanisms: (i) working memory (WM) and attention processes that cause time estimation and time production deficits and (ii) WM and motivational processes that cause time reproduction deficits. Moreover, we found time discrimination deficits in these children as well, but these deficits were not explained by our predictor variables.…”

“…In more detail, successful management of perceptual timing tasks seems to depend on different functions, such as (i) WM which is crucial for holding temporal reference information online during task processing, (ii) attention to time such as attention allocation to the ongoing task and adjustment of motor responses and (iii) inhibition of premature responses 14. Whereas this was found to be true for paradigms that operate in the range of several seconds,5 the body of literature suggests that these mechanisms may also play a role for temporal processing in the range of milliseconds, that is, time discrimination. For WM, it was shown that children and adolescents with ADHD were more impaired in their time discrimination performance depending on the duration of the stimuli that had to be compared with each other (the constant reference stimulus was either presented for 300, 800 or 1200 ms), and WM was associated with task performance at longer (800 ms), but not at shorter (300 ms) presentation duration 13.…”

A short note on the reliability of perceptual timing tasks as commonly used in research on developmental disorders

“…Perceptual timing tasks include paradigms operating in the range of several seconds where participants are asked (1) to provide a verbal duration estimation of a previously presented stimulus (time estimation paradigm), (2) to produce a previously specified time interval by pressing a button (time production paradigm), (3) or to reproduce the duration of a previously presented stimulus by pressing a button (time reproduction paradigm), as well as (4) time discrimination paradigms where participants have to discriminate between stimuli that differ in their duration by tens or hundreds of milliseconds.…”