title: Hemispheric asymmetry of hand representation in human primary somatosensory cortex and handedness.
abstract: OBJECTIVE
  To evaluate interhemispheric differences of hand representation in primary somatosensory (SI) and motor (MI) cortices and its relation to handedness.
  
  
  METHODS
  MRI-based EEG dipole source analysis was performed separately for early (P14, N20, P22) and middle/late latency (P30, N60, N110) SEP components after left and right median nerve stimulation. In addition, the location of the MI hand area (Omega region) and handedness were determined.
  
  
  RESULTS
  Equivalent current dipoles (ECDs) of N20, P30 and N60 SEP components were localized in contralateral SI (area 3b, N20 and P30; area 1, N60), the mean P22 ECD localization was in area 4 of contralateral MI. In contrast to the Omega region and the precentral P22 component, ECDs in both areas 3b and 1 were located more laterally in the right than in the left hemisphere. ECDs in the right SI lay more laterally than the ipsilateral Omega region. Asymmetry in SI was not correlated with handedness.
  
  
  CONCLUSIONS
  The data demonstrate that the location of hand representation shows relevant hemispheric asymmetry in human SI, both in areas 3b and 1.
  
  
  CONCLUSIONS
  Hemispheric asymmetry in SI must be considered in the studies on cortical reorganization and plasticity in SI as well as for transcranial magnetic stimulation (TMS) over SI.
authors.affiliation: Department of Neurology, Johann Wolfgang Goethe-University Frankfurt, Schleusenweg 2-16, 60528 Frankfurt am Main, Germany. Patrick.Jung@em.uni-frankfurt.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Jung
authors.forename: Ulf
authors.initials: U
authors.lastname: Baumgärtner
authors.forename: Walter
authors.initials: W
authors.lastname: Magerl
authors.forename: Rolf-Detlef
authors.initials: RD
authors.lastname: Treede
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography / Q000379:methods; D005069:Evaluation Studies as Topic; D005073:Evoked Potentials, Somatosensory; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008475:Median Nerve / Q000502:physiology / Q000528:radiation effects; D009949:Orientation; D011930:Reaction Time / Q000502:physiology; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D055815:Young Adult