Motor cortex inhibition: a marker of ADHD behavior and motor development in children

Neurology. 2011 Feb 15;76(7):615-21. doi: 10.1212/WNL.0b013e31820c2ebd.


Objective: Attention-deficit/hyperactivity disorder (ADHD) is a childhood-onset behavioral diagnosis in which children often fail to meet age norms in development of motor control, particularly timed repetitive and sequential movements, motor overflow, and balance. The neural substrate of this motor delay may include mechanisms of synaptic inhibition in or adjacent to the motor cortex. The primary objective of this study was to determine whether transcranial magnetic stimulation (TMS)-evoked measures, particularly short interval cortical inhibition (SICI), in motor cortex correlate with the presence and severity of ADHD in childhood as well as with commonly observed delays in motor control.

Methods: In this case-control study, behavioral ratings, motor skills, and motor cortex physiology were evaluated in 49 children with ADHD (mean age 10.6 years, 30 boys) and 49 typically developing children (mean age 10.5 years, 30 boys), all right-handed, aged 8-12 years. Motor skills were evaluated with the Physical and Neurological Examination for Subtle Signs (PANESS) and the Motor Assessment Battery for Children version 2. SICI and other physiologic measures were obtained using TMS in the left motor cortex.

Results: In children with ADHD, mean SICI was reduced by 40% (p < 0.0001) and less SICI correlated with higher ADHD severity (r = -0.52; p = 0.002). Mean PANESS motor development scores were 59% worse in children with ADHD (p < 0.0001). Worse PANESS scores correlated modestly with less SICI (r = -.30; p = 0.01).

Conclusion: Reduced TMS-evoked SICI correlates with ADHD diagnosis and symptom severity and also reflects motor skill development in children.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Attention Deficit Disorder with Hyperactivity / complications*
  • Attention Deficit Disorder with Hyperactivity / pathology*
  • Case-Control Studies
  • Child
  • Developmental Disabilities / complications*
  • Electromyography / methods
  • Evoked Potentials, Motor / physiology
  • Female
  • Humans
  • Logistic Models
  • Male
  • Motor Activity / physiology
  • Motor Cortex / physiopathology*
  • Movement Disorders / etiology*
  • Neural Inhibition / physiology*
  • Psychiatric Status Rating Scales
  • Statistics, Nonparametric