title: A high resolution assessment of the repeatability of relative location and intensity of transcranial magnetic stimulation-induced and volitionally induced blood oxygen level-dependent response in the motor cortex.
abstract: OBJECTIVE
  Using functional magnetic resonance imaging, we assessed variation in location and intensity of blood oxygen level-dependent contrast associated with movements induced by transcranial magnetic stimulation or volition.
  
  
  BACKGROUND
  Anatomic location and within-subject repeatability of blood oxygen level-dependent responses induced by transcranial magnetic stimulation comprise critical information to the use of interleaved transcranial magnetic stimulation/functional magnetic resonance imaging as a neuroscience tool.
  
  
  METHODS
  Eleven healthy adults were scanned 3 times each at 1.5 T. Interleaved with functional magnetic resonance imaging, 1-Hz transcranial magnetic stimulation was applied over motor cortex. VOL was alternated with transcranial magnetic stimulation over the scans.
  
  
  RESULTS
  Intra-subject standard deviations in blood oxygen level-dependent locations ranged between 3 and 6 millimeters, allowing localization to subregions of the motor strip. Coil placement relative to blood oxygen level-dependent location varied more than blood oxygen level-dependent location (sdx = 9.5mm, sdy = 8.7 mm, sdz = 9.0mm) with consistent anterior displacement (dy = 21.8 mm, P = <0.025). Analysis of variance did not detect significant differences between transcranial magnetic stimulation and VOL blood oxygen level-dependent locations or intensities, in contrast to significant intensity differences detected in auditory blood oxygen level dependence.
  
  
  CONCLUSIONS
  The high repeatability of location of transcranial magnetic stimulation-induced blood oxygen level-dependent activation suggests that transcranial magnetic stimulation/functional magnetic resonance imaging stimulation can be used as a precise tool in investigation of cortical mechanisms. The similarity between VOL and transcranial magnetic stimulation suggests that transcranial magnetic stimulation may act through natural brain movement circuits.
authors.affiliation: Center for Advanced Imaging Research and Brain Stimulation Laboratories, Department of Radiology, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Stewart
authors.initials: S
authors.lastname: Denslow
authors.forename: Mikhail
authors.initials: M
authors.lastname: Lomarev
authors.forename: Daryl E
authors.initials: DE
authors.lastname: Bohning
authors.forename: Qiwen
authors.initials: Q
authors.lastname: Mu
authors.forename: Mark S
authors.initials: MS
authors.lastname: George
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000098:blood supply* / Q000502:physiology*; D009068:Movement; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050781:Transcranial Magnetic Stimulation; D014836:Volition
chemical_list: D010100:Oxygen