title: Working memory and intraindividual variability as neurocognitive indicators in ADHD: examining competing model predictions.
abstract: OBJECTIVE
  The current study examined competing predictions of the default mode, cognitive neuroenergetic, and functional working memory models of attention-deficit/hyperactivity disorder (ADHD) regarding the relation between neurocognitive impairments in working memory and intraindividual variability.
  
  
  METHODS
  Twenty-two children with ADHD and 15 typically developing children were assessed on multiple tasks measuring intraindividual reaction time (RT) variability (ex-Gaussian: tau, sigma) and central executive (CE) working memory. Latent factor scores based on multiple, counterbalanced tasks were created for each construct of interest (CE, tau, sigma) to reflect reliable variance associated with each construct and remove task-specific, test-retest, and random error.
  
  
  RESULTS
  Bias-corrected, bootstrapped mediation analyses revealed that CE working memory accounted for 88% to 100% of ADHD-related RT variability across models, and between-group differences in RT variability were no longer detectable after accounting for the mediating role of CE working memory. In contrast, RT variability accounted for 10% to 29% of between-group differences in CE working memory, and large magnitude CE working memory deficits remained after accounting for this partial mediation. Statistical comparison of effect size estimates across models suggests directionality of effects, such that the mediation effects of CE working memory on RT variability were significantly greater than the mediation effects of RT variability on CE working memory.
  
  
  CONCLUSIONS
  The current findings question the role of RT variability as a primary neurocognitive indicator in ADHD and suggest that ADHD-related RT variability may be secondary to underlying deficits in CE working memory.
authors.affiliation: Department of Human Services, University of Virginia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kofler
authors.affiliation: Department of Psychology, Oklahoma State University.
authors.forename: R Matt
authors.initials: RM
authors.lastname: Alderson
authors.affiliation: Department of Psychology, University of Central Florida.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Raiker
authors.affiliation: Department of Psychology, University of Tennessee, Knoxville.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bolden
authors.affiliation: Curry School of Education, University of Virginia.
authors.forename: Dustin E
authors.initials: DE
authors.lastname: Sarver
authors.affiliation: Department of Psychology, University of Central Florida.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Rapport
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications*; D057189:Checklist; D002648:Child; D002755:Choice Behavior; D003072:Cognition Disorders / Q000209:etiology*; D056344:Executive Function / Q000502:physiology; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology*; D015233:Models, Statistical; D009483:Neuropsychological Tests; D011930:Reaction Time