title: Differences of Intracranial Electrical Stimulation Thresholds in the Human Brain.
abstract: BACKGROUND
  The thresholds of current intensities required to evoke a clinical response during intracranial electrical stimulation mapping vary.
  
  
  OBJECTIVE
  We wanted to test if there is systematic variation of threshold currents between different brain areas.
  
  
  METHODS
  Electrode contacts of depth electrodes in a series of patients undergoing presurgical evaluation for epilepsy surgery were stimulated. The brain regions we studied included the insular cortex, the pericentral cortex, and the intervening white matter.
  
  
  RESULTS
  Current intensities that elicited clinical responses in central subcortical white matter tracts were significantly lower than those needed to evoke a clinical response in the cortex.
  
  
  CONCLUSIONS
  We found systematic differences of threshold stimulation intensities between cortical and subcortical structures in the human brain. In addition to known neurophysiologic differences between white and grey matter, the systematic difference in stimulation thresholds may be due to the direction of the white matter tracts with respect to the electrode orientation and to inherent properties of specific brain regions.
authors.affiliation: Department of Clinical Neurophysiology, University Medical Center Goettingen, Robert-Koch-Strasse 40, 37075 Goettingen, Germany; The Neurological Institute, Departments of Neurology, 11100 Euclid Avenue, Cleveland, 44106 OH, USA. Electronic address: CStephani@med.uni-goettingen.de.
authors.forename: C
authors.initials: C
authors.lastname: Stephani
authors.affiliation: The Neurological Institute, Departments of Neurology, 11100 Euclid Avenue, Cleveland, 44106 OH, USA; Department of Neurology, George Washington University, 2150 Pennsylvania Avenue, Washington, 20037 DC, USA.
authors.forename: M
authors.initials: M
authors.lastname: Koubeissi
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods*; D004566:Electrodes; D005260:Female; D006801:Humans; D063189:Symptom Assessment; D066127:White Matter / Q000502:physiology*; D055815:Young Adult
keywords: Depth electrodes; Electrical stimulation; Insula; Threshold currents; White matter