title: Continuous theta burst stimulation of the supplementary motor area: effect upon perception and somatosensory and motor evoked potentials.
abstract: BACKGROUND
  The supplementary motor area (SMA) has been implicated in many aspects of movement preparation and execution. In addition to motor roles, the SMA is responsive to somesthetic stimuli though it is unclear exactly what role the SMA plays in a somatosensory network.
  
  
  OBJECTIVE
  It is the purpose of this study to assess how continuous theta burst stimulation (cTBS) of the SMA affects both somatosensory (SEPs) and motor evoked potentials (MEPs) and if cTBS leads to alterations in tactile perception thresholds of the index fingertip.
  
  
  METHODS
  In experiment 1, cTBS was delivered over scalp sites FCZ (SMA stimulation) (n = 10) and CZ (control stimulation) (n = 10) in separate groups for 40 s (600 pulses) at 90% of participants' resting motor threshold. For both groups, median nerve SEPs were elicited from the right wrist at rest via electrical stimulation (0.5 ms pulse) before and at 10 min intervals post-cTBS out to 30 min (t = pre, 10, 20, and 30 min). Subjects' perceptual thresholds were assessed at similar time intervals as the SEP data using a biothesiometer (120 Hz vibration). In experiment 2 (n = 10) the effect of cTBS to SMA upon single and paired-pulse MEP amplitudes from the right first dorsal interosseous (FDI) was assessed.
  
  
  RESULTS
  cTBS to scalp site FCZ (SMA stimulation) reduced the frontal N30 SEP and increased tactile perceptual thresholds 30 min post-stimulation. However, parietal SEPs and MEP amplitudes from both single and paired-pulse stimulation were unaffected at all time points post-stimulation. cTBS to stimulation site CZ (control) did not result in any physiological or behavioral changes.
  
  
  CONCLUSIONS
  These data demonstrate cTBS to the SMA reduces the amplitude of the N30 coincident with an increase in vibration sensation threshold but does not affect primary somatosensory or motor cortex excitability. The SMA may play a significant role in a somatosensory tactile attention network.
authors.affiliation: Department of Kinesiology, University of Waterloo, 200 University Ave. West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Wynn
authors.initials: W
authors.lastname: Legon
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Dionne
authors.forename: W Richard
authors.initials: WR
authors.lastname: Staines
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*; D055815:Young Adult
keywords: Motor evoked potentials; N30; Somatosensory evoked potentials; Supplementary motor area; Tactile perception; Theta burst stimulation