title: Effects of event probability and sequence on children with attention-deficit/hyperactivity, reading, and math disorder.
abstract: BACKGROUND
  We investigated the impact of stimulus probability and sequence on performance and event-related potentials of 310 children classified into 12 combinations of attention-deficit/hyperactivity disorder (Not-attention-deficit/hyperactivity disorder, Inattentive and Combined subtypes) with presence/absence of reading disorder and math disorder.
  
  
  METHODS
  Subjects pressed buttons to displays of the letters O and X, which were presented with probabilities of either .17/.83 or .50/.50. Greater response selection was required in the .17/.83 condition.
  
  
  RESULTS
  Stimulus probability had comparable effects on all diagnostic groups. The extent of mismatch between a stimulus and preceding events elicited less systematic increases in errors, P3b latency, and P3b amplitude among both attention-deficit/hyperactivity disorder subtypes than controls. Mismatch with preceding trials more greatly reduced math disorder and reading disorder + math disorder children's speed in the Rare task and accuracy in both conditions. Math disorder and reading disorder + math disorder subjects also registered less the effects of alternations of the infrequent O on N2 amplitude and on P3b latency.
  
  
  CONCLUSIONS
  Math disorder and reading disorder + math disorder youngsters' lower sensitivity to sequence irregularity in their event-related potentials along with greater disruption of performance suggest working memory deficits that adversely affected response selection. Comorbidity of attention-deficit/hyperactivity disorder and reading disorder did not affect the results.
authors.affiliation: Meliora Hall, University of Rochester, RC Box 270266, Rochester, NY 14620-0266, USA.
authors.forename: Rafael
authors.initials: R
authors.lastname: Klorman
authors.forename: Joan E
authors.initials: JE
authors.lastname: Thatcher
authors.forename: Sally E
authors.initials: SE
authors.lastname: Shaywitz
authors.forename: Jack M
authors.initials: JM
authors.lastname: Fletcher
authors.forename: Karen E
authors.initials: KE
authors.lastname: Marchione
authors.forename: John M
authors.initials: JM
authors.lastname: Holahan
authors.forename: Karla K
authors.initials: KK
authors.lastname: Stuebing
authors.forename: Bennett A
authors.initials: BA
authors.lastname: Shaywitz
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology; D002648:Child; D004410:Dyslexia / Q000150:complications / Q000503:physiopathology; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007859:Learning Disabilities / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008433:Mathematics; D008568:Memory; D011930:Reaction Time; D013647:Task Performance and Analysis