title: Theta burst repetitive transcranial magnetic stimulation attenuates somatosensory evoked potentials from the lower limb.
abstract: BACKGROUND
  Continuous theta burst stimulation (cTBS) is a form of repetitive transcranial magnetic stimulation which has been shown to alter cortical excitability in the upper limb representation of primary somatosensory cortex (SI). However, it is unknown whether cTBS modulates cortical excitability within the lower limb representation in SI. The present study investigates the effects of cTBS over the SI lower limb representation on cortical somatosensory evoked potentials (SEPs) and Hoffmann reflex (H-reflex) following tibial nerve stimulation at the knee. SEPs and H-reflex were recorded before and in four time blocks up to 30 minutes following cTBS targeting the lower limb representation within SI.
  
  
  RESULTS
  Following cTBS, the P1-N1 first cortical potential was significantly decreased at 12-16 minutes. CTBS also suppressed the P2-N2 second cortical potential for up to 30 minutes following stimulation. The H-reflex remained statistically unchanged following cTBS although there was a modest suppression observed.
  
  
  CONCLUSIONS
  We conclude that cTBS decreases cortical excitability of the lower limb representation of SI as evidenced by suppressed SEP amplitude. The duration and magnitude of the cTBS after effects are similar to those observed in upper limb studies.
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Canada.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Zapallow
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Asmussen
authors.forename: David A E
authors.initials: DA
authors.lastname: Bolton
authors.forename: Kevin G H
authors.initials: KG
authors.lastname: Lee
authors.forename: Mark F
authors.initials: MF
authors.lastname: Jacobs
authors.forename: Aimee J
authors.initials: AJ
authors.lastname: Nelson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D004569:Electroencephalography; D004576:Electromyography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D035002:Lower Extremity / Q000294:innervation*; D008279:Magnetic Resonance Imaging; D008297:Male; D011930:Reaction Time; D013003:Somatosensory Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult