Excitability of motor cortex inhibitory circuits in Tourette syndrome before and after single dose nicotine

Brain. 2005 Jun;128(Pt 6):1292-300. doi: 10.1093/brain/awh473. Epub 2005 Mar 17.


The pathophysiology underlying the involuntary tics of Gilles de la Tourette syndrome (GTS) remains unknown. Here we used transcranial magnetic stimulation (TMS) to examine the excitability of two different inhibitory systems in the human motor cortex: short interval intracortical inhibition (SICI) and short interval afferent inhibition (SAI) in 10 healthy non-smoking controls and eight untreated non-smoking patients with GTS. Compared with the healthy control group, both SICI (measured at a range of conditioning intensities) and SAI were reduced in patients. This is consistent with the suggestion that reduced excitability of cortical inhibition is one factor that contributes to the difficulty that patients have in suppressing involuntary tics. In addition, the reduced SAI indicates that impaired intracortical inhibition may not be limited to the motor cortex but also involves circuits linking sensory input and motor output. A single dose of nicotine reduced tic severity as assessed by blind video scoring in the majority of patients. In addition, it abolished the difference between patients and controls in SICI and SAI. There was no effect of nicotine, and no difference between controls and patients in measures of motor or SICI threshold. This indicates that cholinergic input can modulate the efficiency of SICI and SAI differently in GTS and healthy controls.

Publication types

  • Clinical Trial

MeSH terms

  • Adult
  • Electromyography
  • Evoked Potentials, Motor / drug effects
  • Female
  • Humans
  • Magnetics
  • Male
  • Middle Aged
  • Motor Cortex / drug effects*
  • Motor Cortex / physiopathology
  • Neural Inhibition / drug effects*
  • Neurons, Afferent
  • Nicotine / pharmacology*
  • Nicotine / therapeutic use
  • Nicotinic Agonists / pharmacology
  • Nicotinic Agonists / therapeutic use
  • Severity of Illness Index
  • Tics / drug therapy
  • Tics / physiopathology
  • Tourette Syndrome / drug therapy
  • Tourette Syndrome / physiopathology*


  • Nicotinic Agonists
  • Nicotine