title: Quantifying excessive mirror overflow in children with attention-deficit/hyperactivity disorder.
abstract: OBJECTIVE
  Qualitative observations have revealed that children with attention-deficit/hyperactivity disorder (ADHD) show increased overflow movements, a motor sign thought to reflect impaired inhibitory control. The goal of this study was to develop and implement methods for quantifying excessive mirror overflow movements in children with ADHD.
  
  
  METHODS
  Fifty right-handed children aged 8.2-13.3 years, 25 with ADHD (12 girls) and 25 typically developing (TD) control children (10 girls), performed a sequential finger-tapping task, completing both left-handed (LHFS) and right-handed finger sequencing (RHFS). Phasic overflow of the index and ring fingers was assessed in 34 children with video recording, and total overflow in 48 children was measured by calculating the total angular displacement of the index and ring fingers with electrogoniometer recordings.
  
  
  RESULTS
  Phasic overflow and total overflow across both hands were greater in children with ADHD than in TD children, particularly during LHFS. Separate gender analyses revealed that boys, but not girls, with ADHD showed significantly more total phasic overflow and total overflow than did their gender-matched control children.
  
  
  CONCLUSIONS
  The quantitative overflow measures used in this study support past qualitative findings that motor overflow persists to a greater degree in children with ADHD than in age-matched TD peers. The quantitative findings further suggest that persistence of mirror overflow is more prominent during task execution of the nondominant hand and reveal gender-based differences in developmental neural systems critical to motor control. These quantitative measures will assist future physiologic investigation of the brain basis of motor control in ADHD.
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: L K
authors.initials: LK
authors.lastname: Macneil
authors.forename: P
authors.initials: P
authors.lastname: Xavier
authors.forename: M A
authors.initials: MA
authors.lastname: Garvey
authors.forename: D L
authors.initials: DL
authors.lastname: Gilbert
authors.forename: M E
authors.initials: ME
authors.lastname: Ranta
authors.forename: M B
authors.initials: MB
authors.lastname: Denckla
authors.forename: S H
authors.initials: SH
authors.lastname: Mostofsky
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications / Q000175:diagnosis*; D002648:Child; D005260:Female; D005385:Fingers / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008662:Metacarpophalangeal Joint / Q000503:physiopathology*; D009068:Movement / Q000502:physiology*; D011569:Psychiatric Status Rating Scales; D011596:Psychomotor Disorders / Q000175:diagnosis* / Q000209:etiology; D012737:Sex Factors; D013223:Statistics as Topic