Ahead of the (ROC) Curve: A Statistical Approach to Utilizing Ex-Gaussian Parameters of Reaction Time in Diagnosing ADHD Across Three Developmental Periods.

INTRODUCTION: Performance on executive function (EF) tasks is only modestly predictive of a diagnosis of Attention Deficit Hyperactivity Disorder (ADHD), despite the common assumption that EF deficits are ubiquitous to the disorder. The current study sought to determine whether ex-Gaussian parameters of simple reaction time are better able to discriminate between children and adults with and without ADHD, compared with traditional measures of inhibitory control. METHODS: Receiver Operating Characteristic (ROC) analyses and the area under the curve (AUC) were used to examine the ability of performance on two commonly used tasks of inhibitory control (i.e. stop signal reaction time (SSRT) and go-no-go tasks) to predict ADHD status in preschool (N = 108), middle childhood (N = 309), and young adulthood (N = 133). RESULTS: Across all samples, SSRT, go-no-go percentage of failed inhibits, and standard deviation of reaction (SDRT) time to "go" trials, all successfully discriminated between individuals with and without ADHD. Ex-Gaussian decomposition of the RT distribution indicated that both larger tau and larger sigma drove findings for SDRT. Contrary to predictions, traditional measures of inhibitory control were equal if not better predictors of ADHD status than ex-Gaussian parameters. CONCLUSIONS: Findings support ongoing work to quantify the separate contributions of cognitive subprocesses that drive task performance, which in turn is critical to developing and improving process-based approaches in clinical assessment.

Implementation of the diffusion model on dot-probe task performance in children with behavioral inhibition.

Attentional bias to threat, the process of preferentially attending to potentially threatening environmental stimuli over neutral stimuli, is positively associated with behavioral inhibition (BI) and trait anxiety. However, the most used measure of attentional bias to threat, the dot-probe task, has been criticized for demonstrating poor reliability. The present study aimed to assess whether utilizing a sequential sampling model to describe performance could detect adequate test-retest reliability for the dot-probe task, demonstrate stronger cueing effects, and improve the association with neural signals of early attention. One hundred and twenty children aged 9-12 years completed the dot-probe task twice. During the second administration, event-related potentials (ERPs) were obtained as time-sensitive neural markers of attention. BI was not associated with traditional or diffusion model measures of performance. Traditional and diffusion model measures of performance were also not associated with N1, P2, or N2 ERP amplitude. There were main effects of Visit, in which RTs were faster and standard deviation of RT smaller during the second administration due to an increase in drift rate and a decrease in non-decision time. The traditional RT bias score (r = 0.06) and bias scores formed via diffusion model parameters (all r's < 0.40) all demonstrated poor reliability. Results confirm recommendations to move away from using the dot-probe task as the primary or sole index of attentional bias.

A New Spin on Spatial Cognition in ADHD: A Diffusion Model Decomposition of Mental Rotation.

OBJECTIVES: Multiple studies have found evidence of task non-specific slow drift rate in ADHD, and slow drift rate has rapidly become one of the most visible cognitive hallmarks of the disorder. In this study, we use the diffusion model to determine whether atypicalities in visuospatial cognitive processing exist independently of slow drift rate. METHODS: Eight- to twelve-year-old children with (n = 207) and without ADHD (n = 99) completed a 144-trial mental rotation task. RESULTS: Performance of children with ADHD was less accurate and more variable than non-ADHD controls, but there were no group differences in mean response time. Drift rate was slower, but nondecision time was faster for children with ADHD. A Rotation × ADHD interaction for boundary separation was also found in which children with ADHD did not strategically adjust their response thresholds to the same degree as non-ADHD controls. However, the Rotation × ADHD interaction was not significant for nondecision time, which would have been the primary indicator of a specific deficit in mental rotation per se. CONCLUSIONS: Poorer performance on the mental rotation task was due to slow rate of evidence accumulation, as well as relative inflexibility in adjusting boundary separation, but not to impaired visuospatial processing specifically. We discuss the implications of these findings for future cognitive research in ADHD.

Using inspection time and ex-Gaussian parameters of reaction time to predict executive functions in children with ADHD.

Slower and more variable performance in speeded reaction time tasks is a prominent cognitive signature among children with Attention Deficit Hyperactivity Disorder (ADHD), and is often also negatively associated with executive functioning ability. In the current study, we utilize a visual inspection time task and an ex-Gaussian decomposition of the reaction time data from the same task to better understand which of several cognitive subprocesses (i.e. perceptual encoding, decision-making, or fine-motor output) may be responsible for these important relationships. Consistent with previous research, children with ADHD (n = 190; 68 girls) had longer/slower SD and tau than non-ADHD peers (n = 76; 42 girls), but there were no group differences in inspection time, mu, or sigma. Smaller mu, greater sigma, longer tau, and slower inspection time together predicted worse performance on a latent executive function factor, but only tau partially mediated the relationship between ADHD symptomology and EF. These results suggest that the speed of information accumulation during the decision-making process may be an important mechanism that explains ADHD-related deficits in executive control.

Memory-guided force output is associated with self-reported ADHD symptoms in young adults.

Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed mental health disorder in childhood and persists into adulthood in up to 65 % of cases. ADHD is associated with adverse outcomes such as the ability to gain and maintain employment and is associated with an increased risk for substance abuse obesity workplace injuries and traffic accidents A majority of diagnosed children have motor deficits; however, few studies have examined motor deficits in young adults. This study provides a novel examination of visuomotor control of grip force in young adults with and without ADHD. Participants were instructed to maintain force production over a 20-second trial with and without real-time visual feedback about their performance. The results demonstrated that when visual feedback was available, adults with ADHD produced slightly higher grip force than controls. However, when visual feedback was removed, adults with ADHD had a faster rate of decay of force, which was associated with ADHD symptom severity and trait impulsivity. These findings suggest that there may be important differences in the way that adults with ADHD integrate visual feedback during continuous motor tasks. These may account for some of the motor impairments reported in children with ADHD. These deficits could result from (1) dysfunctional sensory motor integration and/or (2) deficits in short-term visuomotor memory.

A diffusion modeling approach to understanding contextual cueing effects in children with ADHD.

BACKGROUND: Strong theoretical models suggest implicit learning deficits may exist among children with Attention Deficit Hyperactivity Disorder (ADHD). METHOD: We examine implicit contextual cueing (CC) effects among children with ADHD (n = 72) and non-ADHD Controls (n = 36). RESULTS: Using Ratcliff's drift diffusion model, we found that among Controls, the CC effect is due to improvements in attentional guidance and to reductions in response threshold. Children with ADHD did not show a CC effect; although they were able to use implicitly acquired information to deploy attentional focus, they had more difficulty adjusting their response thresholds. CONCLUSIONS: Improvements in attentional guidance and reductions in response threshold together underlie the CC effect. Results are consistent with neurocognitive models of ADHD that posit subcortical dysfunction but intact spatial attention, and encourage the use of alternative data analytic methods when dealing with reaction time data.

Sex differences in the prospective association of excessively long reaction times and hazardous cannabis use at six months.

Objective: The neurocognitive risk mechanisms predicting divergent outcomes likely differ between men and women who use cannabis recreationally. Increasingly, the use of descriptive distributions including the ex-Gaussian has been applied to draw stronger inferences about neurocognitive health in clinical populations. The current project examines whether the long tail of reaction times (RTs) in a distribution, as characterized by the ex-Gaussian parameter tau which may represent difficulty with the regulation of arousal, predicts problematic cannabis use 6 months later in those who use cannabis recreationally, and whether sex moderates these prospective associations. Method: Young adults (ages 18-30, mean age 20.5 years, N =159, 57.2% women, 69.2% Caucasian) who recreationally used cannabis either occasionally (at least once per month) or frequently (three times or more per week) completed the Stroop Color-Word Task at baseline. Ex-Gaussian parameter tau was estimated for each participant. Self-report of hazardous cannabis use (CUDIT-R) and dysregulation of negative (DERS) and positive emotions (DERS-Positive) were obtained at baseline and 6-month follow-up. Results: For those with larger tau at baseline, being a man (but not a woman) was associated with increased difficulty regulating positive emotions concurrently (b = -0.01, F (1,159) = 5.48, p = 0.02), and with hazardous cannabis use six months later (b = -0.007, F (1,159) = 4.42, p = 0.037) after controlling for baseline hazardous cannabis use. Conclusions: Excessively long RTs during cognitive performance may help characterize men at risk for increased hazardous use, which contributes to understanding between-sex heterogeneity in pathways towards cannabis use disorders.

Is reaction time variability in ADHD mainly at low frequencies?

BACKGROUND: Intraindividual variability in reaction times (RT variability) has garnered increasing interest as an indicator of cognitive and neurobiological dysfunction in children with attention deficit hyperactivity disorder (ADHD). Recent theory and research has emphasized specific low-frequency patterns of RT variability. However, whether group differences are specific to low frequencies is not well examined. METHOD: Two studies are presented. The first is a quantitative review of seven previously published studies that have examined patterns of RT variability in ADHD. The second provides new data from a substantially larger sample of children than in prior studies (N(Control) = 42; NADHD = 123). The children completed a choice RT task as part of a traditional go/stop task. Fast-Fourier transform analyses were applied to assess patterns of variability. RESULTS: Quantitative review of previous studies indicated that children with ADHD demonstrate more low-frequency variability than non-ADHD controls (Hedge's g = .39; 95% CI: .16-.62), but an equivalent excess variability in a faster frequency comparison band (g = .36; 95% CI: .03-.69), with a trivial and nonsignificant difference between ESs in each band. New data replicated results of the quantitative review with nearly identical effects in the low-frequency (g = .39; 95% CI: .05-.75) and faster frequency comparison bands (g = .40; 95% CI: .04-.74) and no evidence of diagnosis × frequency interaction (p = .954). CONCLUSIONS: Results suggest that theories of RT variability in ADHD that focus on low-frequency variability will need to be modified to account for the presence of variability at a broader range of frequencies.

Preferential Choice to Exert Cognitive Effort in Children with ADHD: a Diffusion Modelling Account.

Greater sensitivity to the cost of effortful engagement has long been implicated in the development of Attention Deficit Hyperactivity Disorder (ADHD). The current study evaluated preferential choice to engage in demanding tasks, and did so in combination with computational methods to interrogate the process of choice. Children aged 8-12 with (n = 49) and without (n = 36) ADHD were administered the cognitive effort discounting paradigm (COG-ED, adapted from Westbrook et al., 2013). Diffusion modelling was subsequently applied to the choice data to allow for a better description of the process of affective decision making. All children showed evidence of effort discounting, but, contrary to theoretical expectations, there was no evidence that children with ADHD judged effortful tasks to be lower in subjective value, or that they maintained a bias towards less effortful tasks. However, children with ADHD developed a much less differentiated mental representation of demand than their non-ADHD counterparts even though familiarity with and exposure to the experience of effort was similar between groups. Thus, despite theoretical arguments to the contrary, and colloquial use of motivational constructs to explain ADHD-related behavior, our findings strongly argue against the presence of greater sensitivity to costs of effort or reduced sensitivity to rewards as an explanatory mechanism. Instead, there appears to be a more global weakness in the metacognitive monitoring of demand, which is a critical precursor for cost-benefit analyses that underlie decisions to engage cognitive control.

Mechanism-based groups of children with ADHD are associated with distinct domains of impairment.

Person-oriented analyses are commonly used to identify subgroups of children with mental health conditions in the hopes that they will meaningfully inform the taxonomy, assessment, and treatment of psychological disorder. However, whether these data-driven groups are demonstrably better at predicting important aspects of adaptive functioning than standard DSM taxonomy has not been established. Using Attention-Deficit-Hyperactivity-Disorder (ADHD) as a model condition, we utilized dimensions of personality and cognitive ability to identify person-centered profiles of school-aged children (N=246) and evaluated the association of these profiles with critical areas of adaptive functioning. A single profile ("Conscientious") represented non-ADHD controls and was characterized by faster drift rate and higher executive functioning scores. Three profiles ("Disagreeable," "Negative Emotionality," and "Extraverted") were identified for children with ADHD. Drift rate, but not executive functioning, distinguished among ADHD profiles, which were also distinctly associated with comorbid externalizing and internalizing psychopathology, social skills, and academic achievement. In contrast, the Diagnostic and Statistical Manual (DSM) presentations were not informative and showed similar patterns of impairment across domains. Person-centered profiles of children with ADHD are associated with distinct adaptive functioning deficits and may be useful in informing clinical practice.

Frontal alpha asymmetry in anxious school-aged children during completion of a threat identification task.

Asymmetry of EEG alpha power in the frontal lobe has been extensively studied over the past 30 years as a potential marker of emotion and motivational state. However, most studies rely on time consuming manipulations in which participants are placed in anxiety-provoking situations. Relatively fewer studies have examined alpha asymmetry in response to briefly presented emotionally evocative stimuli. If alpha asymmetry can be evoked in those situations, it would open up greater methodological possibilities for examining task-driven changes in neural activation. Seventy-seven children, aged 8-12 years old (36 of whom were high anxious), completed three different threat identification tasks (faces, images, and words) while EEG signal was recorded. Alpha power was segmented and compared across trials in which participants viewed threatening vs. neutral stimuli. Threatening images and faces, but not words, induced lower right vs. left alpha power (greater right asymmetry) that was not present when viewing neutral images or faces. Mixed results are reported for the effect of anxiety symptomatology on asymmetry. In a similar manner to studies of state- and trait-level withdrawal in adults, frontal neural asymmetry can be induced in school-aged children using presentation of brief emotional stimuli.

Manual dexterity and strength and in young adults with and without Attention-Deficit/Hyperactivity Disorder (ADHD).

Manual motor deficits are common in children with attention deficit/hyperactivity disorder (ADHD); however, it is unclear whether these impairments persist into adulthood. The aim of this study was to examine manual dexterity and strength in young adults with ADHD aged 18-25 years. Sixty-one individuals with confirmed ADHD and 56 adults without ADHD completed Purdue Pegboard tasks for manual dexterity and maximal hand- and pinch-grip tests for strength. In the Purdue Pegboard task, participants placed pins using the right, left, and both-hands, respectively. In addition, participants built assemblies using pins, washers, and collars with alternating hand movements. The results demonstrated that women without ADHD out-performed the other three groups in the right-hand, bimanual, and assembly PPB tasks. Both maximal hand strength tests demonstrated that men were stronger than women, but no differences were observed between adults with and without ADHD. The current findings suggest that adults with ADHD may have deficits in manual dexterity and tasks requiring bimanual coordination.

Development of implicit and explicit category learning.

We present two studies that examined developmental differences in the implicit and explicit acquisition of category knowledge. College-attending adults consistently outperformed school-age children on two separate information-integration paradigms due to children's more frequent use of an explicit rule-based strategy. Accuracy rates were also higher for adults on a unidimensional rule-based task due to children's more frequent use of the irrelevant dimension to guide their behavior. Results across these two studies suggest that the ability to learn categorization structures may be dependent on a child's ability to inhibit output from the explicit system.

Examining relationships between executive functioning and delay aversion in attention deficit hyperactivity disorder.

Although motivation and cognition are often examined separately, recent theory suggests that a delay-averse motivational style may negatively impact development of executive functions (EFs), such as working memory (WM) and response inhibition (RI) for children with Attention Deficit Hyperactivity Disorder (ADHD; Sonuga-Barke, 2002 ). This model predicts that performance on delay aversion and EF tasks should be correlated for school-age children with ADHD. However, tests of these relationships remain sparse. Forty-five children ages 8 to 12 with ADHD and 46 non-ADHD controls completed tasks measuring EFs and delay aversion. Children with ADHD had poorer WM and RI than non-ADHD controls, as well as nonsignificantly worse delay aversion. Consistent with previous research, RI was not related to delay aversion. However, delay aversion did predict WM scores for children with and without ADHD. Implications for the dual-pathway hypothesis and future research on cognitive and motivational processing in ADHD are discussed.

Slow drift rate predicts ADHD symptomology over and above executive dysfunction.

Slow drift rate has become one of the most salient cognitive deficits among children with ADHD, and has repeatedly been found to explain slow, variable, and error-prone performance on tasks of executive functioning (EF). The present study applies the diffusion model to determine whether slow drift rate better predicts parent and teacher ratings of ADHD than standard EF metrics. 201 children aged 8-12 completed two tests of speeded decision-making analyzed with the diffusion model and two traditionally scored tests of EF. Latent EF and drift rate factors each independently predicted the general ADHD factor in a bifactor model of ADHD, with poor EF and slow drift rate associated with greater ADHD symptomology. When both EF and drift rate were entered into the model, slow drift rate (but not EF) continued to predict elevated symptomology. These findings suggest that using drift rate to index task performance improves upon conventional approaches to measuring and conceptualizing cognitive dysfunction in ADHD. Implications for future cognitive research in ADHD are discussed.

Neural correlates of working memory's suppression of aversive olfactory distraction effects.

Human cognitive performance is often disrupted by distractions related to aversive stimuli and affective states, but, paradoxically, there is also evidence to suggest that high working memory demands reduce the impact of aversive distraction. Previous empirical work suggests this latter effect occurs because working memory demands reduce attention to off-task processes, but the brain regions that mediate this effect remain uncertain. The current study utilizes a novel distraction manipulation involving unpleasant odorants to identify neural structures that buffer performance from aversive distraction under high working memory demands, and to clarify their connectivity in this context. Twenty-one healthy young adults (12 women) completed a verbal n-back task under two levels of load and were concurrently exposed to either room air or aversive odorants. Three brain regions displayed increases in neural responses to olfactory distractors under high load only; the left dorsolateral prefrontal cortex, the left ventrolateral prefrontal cortex and right cerebellar Crus I. Of these regions, only the ventrolateral prefrontal cortex also displayed context-specific connectivity with a region thought to be involved in off-task processes: the dorsomedial prefrontal cortex. Overall, results suggest that, under high working memory demands, areas of the prefrontal cortex and cerebellum shield cognition from aversive distraction, potentially through interactions with brain structures involved in off-task processes.

Test-Retest Reliability and Measurement Invariance of Executive Function Tasks in Young Children With and Without ADHD.

Objective: Measurement reliability is assumed when executive function (EF) tasks are used to compare groups or to examine relationships between cognition and etiologic and maintaining factors of psychiatric disorders. However, the test-retest reliabilities of many commonly used EF tasks have rarely been examined in young children. Furthermore, measurement invariance between typically developing and psychiatric populations has not been examined. Method: Test-retest reliability of a battery of commonly used EF tasks was assessed in a group of children between the ages of 5 and 6 years old with (n = 63) and without (n = 44) ADHD. Results: Few individual tasks achieved adequate reliability. However, confirmatory factor analysis (CFA) models identified two factors, working memory and inhibition, with test-retest correlations approaching 1.0. Multiple indicators multiple causes (MIMIC) models confirmed configural measurement invariance between the groups. Conclusion: Problems created by poor reliability, including reduced power to detect group differences, index change over time, or to identify relationships with other measures, may be mitigated using latent variable approaches.

Making the Most of It: Application of Planned Missingness Design to Increase the Efficiency of Diagnostic Assessment.

Multimethod assessment is recommended as "best practice" in clinical assessment and is often implemented through the combined use of symptom rating scales and structured interviews. While this approach increases confidence in the validity of assessment, it also increases burden, expense, and leads to the accumulation of redundant information. To address this problem, we evaluate the use a planned missingness design within the framework of adult Attention Deficit/Hyperactivity Disorder (ADHD) assessment. In a sample of 169 young adults, we fit a two-method measurement (TMM) model using ADHD symptoms obtained from rating scales and a structured diagnostic interview. Based on an estimated 8:1 differential between the cost of conducting an in-person diagnostic interview vs. completing questionnaires online, we conducted a series of Monte Carlo simulations to determine the utility of combining TMM with a planned missingness design. We find that even when costs are kept constant, statistical power of the TMM/planned missingness design was equal to the power that would have been obtained had nearly twice the number of participants with complete data been recruited. Conversely, costs could be decreased by 20-25%, while maintaining statistical power equivalent to a design with complete data. Our results suggest the TMM design is a promising technique for reducing the cost and burden of diagnostic assessment within research settings.

A diffusion model analysis of sustained attention in children with attention deficit hyperactivity disorder.

OBJECTIVE: Whether children with attention deficit hyperactivity disorder (ADHD) have deficits in sustained attention remains unresolved due to the ongoing use of cognitive paradigms that are not optimized for studying vigilance and the fact that relatively few studies report performance over time. METHOD: In three independent samples of school-age children with (total N = 128) and without ADHD (total N = 59), we manipulated event rate, difficulty of discrimination, and use signal detection (SDT) and diffusion models (DM) to evaluate the cause of the vigilance decrement during a continuous performance task. RESULTS: For both groups of children, a bias toward "no-go" over time (as indexed by the SDT parameter B″ and the DM parameter z/a) was responsible for generating the vigilance decrement. However, among children with ADHD, the rate at which information accumulated to make a no-go decision (vNoGo) also increased with time on task, representing a possible secondary mechanism that biases children against engagement. At all time points, children with ADHD demonstrated reduced sensitivity to discriminate targets from nontargets. CONCLUSION: Children with ADHD are particularly sensitive to the cost of task engagement, but nonspecific slower drift rate may ultimately provide a better conceptualization of the cognitive atypicalities commonly observed in that group. Results are interpreted in the context of updated conceptualizations of sustained attention and vigilance. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Abnormal spatial asymmetry of selective attention in ADHD.

BACKGROUND: Evidence for a selective attention abnormality in children with attention deficit hyperactivity disorder (ADHD) has been hard to identify using conventional methods from cognitive science. This study tested whether the presence of selective attention abnormalities in ADHD may vary as a function of perceptual load and target lateralisation. Given evidence of right-hemisphere dysfunction in ADHD we predicted increased interference effects for right, but not left-sided target displays, particularly under low perceptual load. METHOD: Fourteen children with ADHD-C and 14 typically developing children were tested on a modified flanker task under low and high perceptual load. We also sought evidence for our hypothesis in a re-analysis of an independent data set (42 ADHD; 34 typically developing) in which load effects on selective attention in ADHD were previously examined (Huang-Pollock, Nigg, & Carr, 2005). RESULTS: As predicted, all children showed evidence of greater interference by flankers under low compared with high perceptual load conditions. Crucially, however, children with ADHD showed the greatest interference effect for right-sided target displays under low but not high perceptual load. In contrast, typically developing children showed the greatest interference for left-sided target displays. The magnitude of interference for right-sided targets was also positively correlated with ADHD symptom levels. Re-analysis of an independent data set (Huang-Pollock et al., 2005) further confirmed our findings. CONCLUSIONS: This study demonstrates that interference effects in children with ADHD and typically developing children are spatially asymmetrical but opposite in direction. The pattern of right-sided interference effects in children with ADHD suggests disruption within right hemisphere attentional networks in ADHD.