title: Reproducibility of functional MRI localization within the human somatosensory cortex.
abstract: OBJECTIVE
  To evaluate the effect of fMRI localization approaches and region size on the reproducibility of digit localization in the human somatosensory cortex.
  
  
  METHODS
  Vibrotactile stimulation was applied to digits 2 and 4 producing cortical activation sites relating to each digit. Thirteen subjects were scanned twice on separate occasions in a 3 Tesla scanner using a voxel size of 2 mm. Regions of activity were thresholded to different sizes varying from 50 to 1000 voxels. Three measures of position were acquired from these regions: center of gravity (COG), center co-ordinate and peak voxel. To account for registration errors, Euclidean distance between the two digits was computed. Reproducibility was determined in terms of the 95% confidence interval for individual position in X, Y, and Z and also the distance between the two digit locations.
  
  
  RESULTS
  Region size of 200 most significant voxels was shown to have the best reproducibility. Center co-ordinate proved to be the most precise form of localizing activity with a 95% CI of 2.1 mm, 2.6 mm, and 3.1 mm in the X, Y, and Z axes. Euclidean distance between the center co-ordinates of the two digit activation sites was shown to be a reliable means of overcoming registration errors with a 95% CI of 1.7 mm.
  
  
  CONCLUSIONS
  This study shows a high level of reproducibility for fMRI localization in the somatosensory system.
authors.affiliation: School of Cancer and Enabling Sciences, University of Manchester, Stopford Building, Manchester, United Kingdom. rishma.vidyasagar@manchester.ac.uk
authors.forename: Rishma
authors.initials: R
authors.lastname: Vidyasagar
authors.forename: Laura M
authors.initials: LM
authors.lastname: Parkes
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D015203:Reproducibility of Results; D013003:Somatosensory Cortex / Q000502:physiology*; D014110:Touch; D014732:Vibration