title: Bidirectional modulation of sensory cortical excitability by quadripulse transcranial magnetic stimulation (QPS) in humans.
abstract: OBJECTIVE
  Quadripulse transcranial magnetic stimulation (QPS) is a newly designed patterned repetitive transcranial magnetic stimulation (TMS). Previous studies of QPS showed bidirectional effects on the primary motor cortex (M1), which depended on its inter-stimulus interval (ISI): motor evoked potentials (MEPs) were potentiated at short ISIs and depressed at long ISIs (homotopic effects). These physiological characters were compatible with synaptic plasticity. In this research, we studied effects of QPS on the primary sensory cortex (S1).
  
  
  METHODS
  One burst consisted of four monophasic TMS pulses at an intensity of 90% active motor threshold. The ISI of four pulses was set at 5 ms (QPS-5) or at 50 ms (QPS-50). Same bursts were given every 5s for 30 min. QPS-5 and QPS-50 were performed over three areas (M1, S1 and dorsal premotor cortex (dPMC)). One sham stimulation session was also performed. Excitability changes of S1 were evaluated by timeline of somatosensory evoked potentials (SEPs).
  
  
  RESULTS
  QPS-5 over M1 or dPMC enhanced the P25-N33 component of SEP, and QPS-50 over M1 depressed it. By contrast, QPSs over S1 had no effects on SEPs.
  
  
  CONCLUSIONS
  QPSs over motor cortices modulated the S1 cortical excitability (heterotopic effects). Mutual connections between dPMC or M1 and S1 might be responsible for these modulations.
  
  
  CONCLUSIONS
  QPSs induced heterotopic LTP or LTD-like cortical excitability changes.
authors.affiliation: Department of Neurology, School of Medicine, Fukushima Medical University, Fukushima, Japan. setsu-tky@umin.ac.jp
authors.forename: Setsu
authors.initials: S
authors.lastname: Nakatani-Enomoto
authors.forename: Ritstuko
authors.initials: R
authors.lastname: Hanajima
authors.forename: Masashi
authors.initials: M
authors.lastname: Hamada
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Terao
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Shirota
authors.forename: Shingo
authors.initials: S
authors.lastname: Okabe
authors.forename: Masaki
authors.initials: M
authors.lastname: Hirose
authors.forename: Koichiro
authors.initials: K
authors.lastname: Nakamura
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Furubayashi
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Mochizuki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Enomoto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ugawa
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*