title: Does processing speed mediate the effect of pediatric traumatic brain injury on working memory?
abstract: OBJECTIVE
  Processing speed (PS) and working memory (WM), core abilities that support learning, are vulnerable to disruption following traumatic brain injury (TBI). Developmental increases in WM are related to age-related changes in PS. The purpose of this study was to investigate whether WM deficits in children with TBI are mediated by PS.
  
  
  METHODS
  The performance of children with complicated mild, moderate, and severe TBI (n = 77) was examined relative to an orthopedic injury (n = 30) and a healthy comparison group (n = 40) an average of 4 years after injury (range 8 months to 12 years). Coding was utilized as a measure of PS, while the WM measures included complex verbal and visual-spatial span tasks with parallel processing requirements. Mediation analysis examined whether TBI might have an indirect effect on WM through PS.
  
  
  RESULTS
  Children in the TBI group performed more poorly than the combined comparison groups on coding and visual-spatial WM. Verbal WM scores were lower in TBI and the healthy comparison relative to the orthopedic group. TBI severity group differences were found on coding, but not WM measures. The relation between coding and both the WM tasks was similar. Bootstrap regression analyses suggested that PS, as measured by coding, might partially mediate the effect of group performance on WM.
  
  
  CONCLUSIONS
  TBI disrupts core PS and WM abilities that scaffold more complex abilities. Importantly, slowed PS was associated with WM deficits commonly identified following pediatric TBI. Implications of our findings regarding the relation between PS and WM may suggest interventions for children and adolescents following TBI.
authors.affiliation: Department of Pediatrics and Children's Learning Institute, University of Texas Health Science Center at Houston.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Gorman
authors.affiliation: Department of Pediatrics and Children's Learning Institute, University of Texas Health Science Center at Houston.
authors.forename: Marcia A
authors.initials: MA
authors.lastname: Barnes
authors.affiliation: School of Public Health, University of Texas Health Science Center at Houston.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Swank
authors.affiliation: Department of Pediatrics and Children's Learning Institute, University of Texas Health Science Center at Houston.
authors.forename: Mary
authors.initials: M
authors.lastname: Prasad
authors.affiliation: Department of Pediatric Surgery, University of Texas Health Sciences Center at Houston.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Cox
authors.affiliation: Department of Pediatrics and Children's Learning Institute, University of Texas Health Science Center at Houston.
authors.forename: Linda
authors.initials: L
authors.lastname: Ewing-Cobbs
mesh_terms: D000293:Adolescent; D001307:Auditory Perception; D001930:Brain Injuries / Q000523:psychology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007223:Infant; D007361:Intelligence Tests; D008137:Longitudinal Studies; D008297:Male; D008569:Memory Disorders / Q000209:etiology / Q000523:psychology*; D008570:Memory, Short-Term; D009035:Mothers; D011446:Prospective Studies; D011597:Psychomotor Performance