title: Intra-subject reliability of parameters contributing to maps generated by transcranial magnetic stimulation in able-bodied adults.
abstract: OBJECTIVE
  This study evaluated the reliability of several parameters contributing to topographic motor cortical maps of the extensor digitorum communis (EDC) within able-bodied participants, across 3 sessions and from both hemispheres with greater precision than previously reported.
  
  
  METHODS
  Nine healthy right-handed males aged 44-75 years were studied at 3 separate sessions, spaced 7-14 days apart. Transcranial magnetic stimulation (TMS) was used to elicit motor evoked potentials (MEP) in the contralateral EDC. Closely spaced surface electrodes were used to record the MEPs.
  
  
  RESULTS
  TMS-related parameters did not demonstrate a significant difference within participants across sessions and between hemispheres, with the exception of the hotspot distance, center of gravity distance, and normalized map volume. Hotspot and COG distances were determined from the Euclidean equation to calculate the distance in x,y coordinates traveled over sessions: one to two (distance A) and two to three (distance B). The hotspot distance, center of gravity distance and normalized map volume demonstrated a significant difference between right and left hemispheres, within participants. Adjusting for time and examining mean changes for hemispheres across sessions revealed that there was a 9-fold greater movement over sessions in the left hemisphere among these variables.
  
  
  CONCLUSIONS
  TMS-related parameters are reliable within participants across 3 sessions. These data should be useful for planning and interpreting TMS studies using a healthy or patient population before and after an intervention.
authors.affiliation: Department of Rehabilitation Medicine, Emory University School of Medicine, 1441 Clifton Road, NE, Atlanta, GA 30322, USA. swolf@emory.edu
authors.forename: Steven L
authors.initials: SL
authors.lastname: Wolf
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Butler
authors.forename: Georgette I
authors.initials: GI
authors.lastname: Campana
authors.forename: Trinity A
authors.initials: TA
authors.lastname: Parris
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Struys
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Weinstein
authors.forename: Paul
authors.initials: P
authors.lastname: Weiss
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001931:Brain Mapping / Q000379:methods*; D055590:Electromagnetic Phenomena / Q000379:methods* / Q000592:standards*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results