title: A comparative study of the effects of repetitive paired transcranial magnetic stimulation on motor cortical excitability.
abstract: OBJECTIVE
  Various methods of application of repetitive transcranial magnetic stimulation (TMS) have been evaluated for their potential capacity to alter motor cortical excitability. Initial research suggests that the repetitive application of paired TMS pulses (repetitive paired pulse TMS (rppTMS)) may have greater effects on cortical excitability, perhaps through the facilitation of I-wave interaction. We aimed to compare the post-train effects of 15 min trains of rppTMS to investigate the potential therapeutic application of this technique as well as to compare it to a standard high frequency repetitive TMS paradigm.
  
  
  METHODS
  Ten normal subjects received three 15 min sessions of rppTMS, 5 Hz high frequency rTMS and sham TMS in randomised order. rppTMS consisted of a single train of 180 pulse pairs (0.2 Hz, 1.5 ms inter-stimulus interval, supra-threshold intensity) administered over 15 min. The rTMS condition involved 750 pulses provided in 5s 5 Hz trains with a 25s inter-train interval at 90% of the RMT. Motor evoked potential size and cortical silent period duration were assessed before and after each session.
  
  
  RESULTS
  There were no significant changes in cortical excitability produced by any of the stimulation conditions. Five hertz rTMS produced an increase in cortical silent period duration (p=0.004) which was not affected by rppTMS.
  
  
  CONCLUSIONS
  Fifteen minutes trains of 1.5ms rppTMS do not substantially increase post train cortical excitability. Repetitive brief trains of 5Hz rTMS also do not alter excitability but appear to effect cortical inhibition.
authors.affiliation: Alfred Psychiatry Research Centre, The Alfred and Monash University School of Psychiatry, Psychology and Psychological Medicine, Commercial Road, Melbourne, Victoria 3004, Australia. paul.fitzgerald@med.monash.edu.au
authors.forename: Paul B
authors.initials: PB
authors.lastname: Fitzgerald
authors.forename: Sarah
authors.initials: S
authors.lastname: Fountain
authors.forename: Kate
authors.initials: K
authors.lastname: Hoy
authors.forename: Jerome
authors.initials: J
authors.lastname: Maller
authors.forename: Peter
authors.initials: P
authors.lastname: Enticott
authors.forename: Robin
authors.initials: R
authors.lastname: Laycock
authors.forename: Daniel
authors.initials: D
authors.lastname: Upton
authors.forename: Zafiris J
authors.initials: ZJ
authors.lastname: Daskalakis
mesh_terms: D000328:Adult; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D009482:Neurophysiology / Q000295:instrumentation / Q000379:methods*; D011712:Pyramidal Tracts / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods*