title: Attention and inhibition in children with ASD, ADHD and co-morbid ASD + ADHD: an event-related potential study.
abstract: BACKGROUND
  Substantial overlap has been reported between attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Deficits in executive function (EF) are characteristic of both disorders but these impairments have not been compared directly across pure and co-morbid cases using event-related potentials (ERPs).
  
  
  METHODS
  Behavioural parameters and ERPs were recorded during a flankered cued-continuous performance test (CPT-OX) administered to 8-13-year-old boys with ASD (n = 19), ADHD (n = 18), co-morbid ASD + ADHD (n = 29) and typically developing controls (TD; n = 26). Preparatory processing (contingent negative variation, CNV) and attentional orienting (Cue-P3) at cues, response execution at targets (Go-P3), inhibitory processing at non-targets (NoGo-P3) and conflict monitoring between target and non-target trials (Go-N2 v. NoGo-N2) were examined.
  
  
  RESULTS
  Categorical diagnoses and quantitative trait measures indicated that participants with ADHD (ADHD/ASD + ADHD) made more omission errors and exhibited increased reaction-time (RT) variability and reduced amplitude of the Cue-P3 and NoGo-P3 compared to TD/ASD participants. Participants with ASD (ASD/ ASD + ADHD) demonstrated reduced N2 enhancement from Go to NoGo trials compared to TD/ADHD participants. Participants with ASD-only displayed enhanced CNV amplitude compared to ASD + ADHD and TD participants.
  
  
  CONCLUSIONS
  Children with ADHD show deficits in attentional orienting and inhibitory control whereas children with ASD show abnormalities in conflict monitoring and response preparation. Children with co-morbid ASD + ADHD present as an additive co-occurrence with deficits of both disorders, although non-additive effects are suggested for response preparation. Measuring ERPs that index attention and inhibition is useful in disentangling cognitive markers of ASD and ADHD and elucidating the basis of co-occurring ASD + ADHD to guide clinical assessment.
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Tye
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, UK.
authors.forename: P
authors.initials: P
authors.lastname: Asherson
authors.affiliation: Child and Adolescent Psychiatry, Institute of Psychiatry, King's College London, UK.
authors.forename: K L
authors.initials: KL
authors.lastname: Ashwood
authors.affiliation: Child and Adolescent Psychiatry, Institute of Psychiatry, King's College London, UK.
authors.forename: B
authors.initials: B
authors.lastname: Azadi
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, UK.
authors.forename: P
authors.initials: P
authors.lastname: Bolton
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, UK.
authors.forename: G
authors.initials: G
authors.lastname: McLoughlin
mesh_terms: D000293:Adolescent; D001288:Attention / Q000502:physiology*; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000503:physiopathology*; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology / Q000503:physiopathology*; D015897:Comorbidity; D003265:Contingent Negative Variation / Q000502:physiology; D018913:Event-Related Potentials, P300 / Q000502:physiology; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*