title: Short- and intermediate-interval cortical inhibition and facilitation assessed by navigated transcranial magnetic stimulation.
abstract: OBJECTIVE
  To characterize the behaviour of primary motor cortex and to determine appropriate measurement parameters for short-interval cortical inhibition (SICI) and intracortical facilitation (ICF) by paired-pulse transcranial magnetic stimulation (TMS) with the aid of MRI-based neuronavigation.
  
  
  METHODS
  Paired-pulse TMS was targeted to the optimal cortical representation sites of the abductor pollicis brevis (APB) muscle in 48 healthy right-handed volunteers. Motor evoked potentials (MEPs) were recorded from the APB and abductor digiti minimi (ADM) muscles. The conditioning stimulus (CS) intensities were 80% and 90% and the test stimulus was 120% of the resting motor threshold (rMT). The interstimulus intervals (ISIs) were 3, 7, 13, 22 and 28 ms.
  
  
  RESULTS
  Inhibition was observed at 3 ms with a CS of 80%. Facilitation emerged at ISIs of 7 and 13 ms with both CS intensities, more prominently with 90%. At ISI of 22 ms, facilitation was observed in ADM (p<0.01) but not in APB. No uniform amplitude change was observed at ISI of 28 ms. For both muscles, MEP latencies were shortened (p<0.01) at ISIs of 3 and 7 ms and prolonged (p<0.01) at 28 ms.
  
  
  CONCLUSIONS
  Inhibition is most prominent at ISI of 3 ms and CS of 80% of rMT, whereas CS of 90% of rMT and ISIs of 7 and 13 ms are preferable for facilitation. Latencies appear to be stable and independent indicators of both phenomena should be taken into account.
  
  
  CONCLUSIONS
  Both the latency and amplitude of MEPs are important parameters when paired-pulse paradigms are used in clinical studies.
authors.affiliation: Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland. laura.saisanen@kuh.fi
authors.forename: Laura
authors.initials: L
authors.lastname: Säisänen
authors.forename: Petro
authors.initials: P
authors.lastname: Julkunen
authors.forename: Eini
authors.initials: E
authors.lastname: Niskanen
authors.forename: Taina
authors.initials: T
authors.lastname: Hukkanen
authors.forename: Esa
authors.initials: E
authors.lastname: Mervaala
authors.forename: Jari
authors.initials: J
authors.lastname: Karhu
authors.forename: Mervi
authors.initials: M
authors.lastname: Könönen
mesh_terms: D000328:Adult; D000368:Aged; D016001:Confidence Intervals; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult