title: Diminished modulation of preparatory sensorimotor mu rhythm predicts attention-deficit/hyperactivity disorder severity.
abstract: BACKGROUND
  Attention-deficit/hyperactivity disorder (ADHD) is characterized by problems in regulating attention and in suppressing disruptive motor activity, i.e. hyperactivity and impulsivity. We recently found evidence that aberrant distribution of posterior α band oscillations (8-12 Hz) is associated with attentional problems in ADHD. The sensorimotor cortex also produces strong 8-12 Hz band oscillations, namely the μ rhythm, and is thought to have a similar inhibitory function. Here, we now investigate whether problems in distributing α band oscillations in ADHD generalize to the μ rhythm in the sensorimotor domain.
  
  
  METHODS
  In a group of adult ADHD (n = 17) and healthy control subjects (n = 18; aged 21-40 years) oscillatory brain activity was recorded using magnetoencephalography during a visuo-spatial attention task. Subjects had to anticipate a target with unpredictable timing and respond by pressing a button.
  
  
  RESULTS
  Preparing a motor response, the ADHD group failed to increase hemispheric μ lateralization with relatively higher μ power in sensorimotor regions not engaged in the task, as the controls did (F 1,33 = 8.70, p = 0.006). Moreover, the ADHD group pre-response μ lateralization not only correlated positively with accuracy (r s = 0.64, p = 0.0052) and negatively with intra-individual reaction time variability (r s = -0.52, p = 0.033), but it also correlated negatively with the score on an ADHD rating scale (r s = -0.53, p = 0.028).
  
  
  CONCLUSIONS
  We suggest that ADHD is associated with an inability to sufficiently inhibit task-irrelevant sensorimotor areas by means of modulating μ oscillatory activity. This could explain disruptive motor activity in ADHD. These results provide further evidence that impaired modulation of α band oscillations is involved in the pathogenesis of ADHD.
authors.affiliation: Karakter Child and Adolescent Psychiatry University Centre,Nijmegen,The Netherlands.
authors.forename: N
authors.initials: N
authors.lastname: Ter Huurne
authors.affiliation: Donders Institute for Brain,Cognition and Behaviour,Radboud University,Nijmegen,The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Lozano-Soldevilla
authors.affiliation: Department of Human Genetics,Radboudumc,Nijmegen,The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Onnink
authors.affiliation: Department of Psychiatry,Radboudumc,Nijmegen,The Netherlands.
authors.forename: C
authors.initials: C
authors.lastname: Kan
authors.affiliation: Karakter Child and Adolescent Psychiatry University Centre,Nijmegen,The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Buitelaar
authors.affiliation: Centre for Human Brain Health,School of Psychology,University of Birmingham,Birmingham,UK.
authors.forename: O
authors.initials: O
authors.lastname: Jensen
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological / Q000502:physiology; D001288:Attention / Q000502:physiology*; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D058256:Brain Waves / Q000502:physiology*; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D015225:Magnetoencephalography; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D066191:Sensorimotor Cortex / Q000503:physiopathology*; D012720:Severity of Illness Index; D013028:Space Perception / Q000502:physiology; D014796:Visual Perception / Q000502:physiology; D055815:Young Adult
keywords: Alpha activity; attention-deficit/hyperactivity disorder; inhibition; magnetoencephalography; mu rhythm