title: The Resting Motor Threshold--Restless or Resting? A Repeated Threshold Hunting Technique to Track Dynamic Changes in Resting Motor Threshold.
abstract: BACKGROUND
  The resting motor threshold (RMT) is used to individually adjust the intensity of transcranial magnetic stimulation (TMS) intensity and is assumed to be stable. Here we challenge this notion by showing that RMT expresses acute context-dependent fluctuations.
  
  
  METHODS
  In twelve participants, the RMT of the right first dorsal interosseus muscle was repeatedly determined using a threshold-hunting procedure while participants performed motor imagery and visual attention tasks with the right or left hand. Data were analyzed using repeated-measure ANOVA.
  
  
  RESULTS
  RMT differed depending on which hand performed the task (P = 0.003). RMT of right FDI was lower during motor imagery than during visual attention of the right hand (P = 0.002), but did not differ between left-hand tasks (P = 0.988).
  
  
  CONCLUSIONS
  State-dependent changes of RMT occur in absence of overt motor activity and can be captured online by threshold hunting. These fluctuations need to be considered when RMT is used to individually adjust TMS intensity for plasticity-inducing protocols.
authors.affiliation: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Copenhagen, Denmark. Electronic address: ankenk@drcmr.dk.
authors.forename: Anke Ninija
authors.initials: AN
authors.lastname: Karabanov
authors.affiliation: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Fonctions Cérébrals et Neuromodulation, Université Joseph Fourier, Grenoble, France; Inserm, U836, Grenoble Institut des Neurosciences, Grenoble, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Raffin
authors.affiliation: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark.
authors.forename: Hartwig Roman
authors.initials: HR
authors.lastname: Siebner
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D018592:Cross-Over Studies; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D007092:Imagination / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011897:Random Allocation; D012146:Rest / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: Motor evoked potential; Motor imagery; Resting motor threshold; Transcranial magnetic stimulation