title: Ongoing cumulative effects of single TMS pulses on corticospinal excitability: An intra- and inter-block investigation.
abstract: OBJECTIVE
  To evaluate the effects of several single TMS pulses, delivered at two different inter-trial intervals (ITIs), on corticospinal excitability.
  
  
  METHODS
  Twelve healthy volunteers participated in two experimental sessions, during which TMS pulses were delivered at random or at fixed ITIs. The TMS single pulse-induced modulation of corticospinal output (motor evoked potential amplitude - MEP) was evaluated on-line. Each session began with a baseline block, followed by 10 blocks, with 20 TMS pulses each. Intra- and inter-block effects were valuated using an ANOVA model, through nested random effect on subjects considering the subject-specific variability.
  
  
  RESULTS
  The delivery of successive TMS pulses significantly changed both intra-block and inter-block cortical excitability, as demonstrated by an increase in the amplitude of MEPs (p<0.001) and supported through trend analyses, showing a perfect linear trend for inter-block levels (R(2)=1) and nearly linear trend for intra-block levels (R(2)=0.97). The MEPs significantly increased when the TMS pulses were delivered at both random and fixed ITIs.
  
  
  CONCLUSIONS
  Single TMS pulses induce cumulative changes in neural activity during the same stimulation, resulting in a motor cortical excitability increase.
  
  
  CONCLUSIONS
  Particular attention should be taken when several single TMS pulses are delivered in research and clinical settings for diagnostic and therapeutic purposes.
authors.affiliation: Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy. Electronic address: mariaconcetta.pellicciari@cognitiveneuroscience.it.
authors.forename: Maria Concetta
authors.initials: MC
authors.lastname: Pellicciari
authors.affiliation: Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy; Neuroscience Section, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Miniussi
authors.affiliation: Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy.
authors.forename: Clarissa
authors.initials: C
authors.lastname: Ferrari
authors.affiliation: Non-invasive Brain Stimulation Unit, Department of Clinical and Behavioral Neurology, IRCCS Santa Lucia Foundation, Rome, Italy; Stroke Unit, Department of Neuroscience, Policlinic Tor Vergata, Rome, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
authors.affiliation: Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Bortoletto
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods / Q000639:trends*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods / Q000639:trends*; D055815:Young Adult
keywords: Corticospinal excitability; Motor evoked potentials (MEP); Random and fixed inter-trial interval; Single pulse; Transcranial magnetic stimulation (TMS)