Impaired transcallosally mediated motor inhibition in adults with attention-deficit/hyperactivity disorder is modulated by methylphenidate

J Neural Transm (Vienna). 2008 May;115(5):777-85. doi: 10.1007/s00702-007-0008-1. Epub 2008 Jan 15.


Using transcranial magnetic stimulation (TMS) in children with ADHD, an impaired transcallosally mediated motor inhibition (ipsilateral silent period, iSP) was found, and its restoration was correlated with improvement of hyperactivity under medication with methylphenidate (MPH). Hyperactivity has been reported to decrease during transition into adulthood, although some motor dysfunction might persist. As one underlying neurophysiological process, a development-dependent normalization of motor cortical excitability might be postulated. In order to test this hypothesis, we measured the iSP in 21 adult ADHD patients and twenty-one sex- and age-matched healthy controls. In 16 of these patients, a second TMS was performed under treatment with MPH. Our results indicate a persistence of impaired transcallosally mediated motor cortical inhibition (shortened duration) in ADHD adults, which was correlated with clinical characteristics of hyperactivity and restlessness, and was restored by MPH. In contrast to ADHD in childhood, the iSP latency was not impaired, suggesting a partial development-dependent normalization of motor cortical excitability in ADHD adults. ISP duration appears to be a sensitive parameter for the assessment of disturbed intercortical inhibition in adults with ADHD.

Publication types

  • Controlled Clinical Trial

MeSH terms

  • Adult
  • Attention Deficit Disorder with Hyperactivity / drug therapy*
  • Attention Deficit Disorder with Hyperactivity / physiopathology*
  • Case-Control Studies
  • Central Nervous System Stimulants / therapeutic use*
  • Electric Stimulation / methods
  • Evoked Potentials, Motor / drug effects*
  • Evoked Potentials, Motor / physiology
  • Evoked Potentials, Motor / radiation effects
  • Female
  • Functional Laterality / drug effects
  • Humans
  • Inhibition, Psychological*
  • Male
  • Methylphenidate / therapeutic use*
  • Reaction Time / drug effects
  • Reaction Time / radiation effects
  • Regression Analysis
  • Transcranial Magnetic Stimulation


  • Central Nervous System Stimulants
  • Methylphenidate