title: Cortico-cortical evoked hemodynamic responses in human language systems using intraoperative near-infrared spectroscopy during direct cortical stimulation.
abstract: BACKGROUND
  Understanding of cortico-cortical activity in eloquent areas intraoperatively is crucial for neurosurgical procedures. Here, we used intraoperative near-infrared spectroscopy (iNIRS) during direct cortical stimulation as a robust tool to better understand the cortico-cortical connectivity in language systems.
  
  
  METHODS
  We applied iNIRS to 3 patients who underwent epilepsy surgery due to lesions (cavernous angioma, epidermoid cyst, and low-grade glioma) located in language areas. Using iNIRS, we measured the blood concentration changes of oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR) in the lateral temporal cortex during direct cortical stimulation (50Hz) at the inferior frontal area where Broca's area was probabilistically located.
  
  
  RESULTS
  In all patients, 50Hz stimulation elicited hemodynamic changes in the superior temporal gyrus (STG). During 0.8-4.8s after stimulation, HbO2 increased and HbR decreased in the posterior part of the STG (Wernicke's area). Similar responses were observed in the anterior part of the STG 1.3-8.0s after stimulation. Finally, these changes were disappeared in the middle temporal gyrus.
  
  
  CONCLUSIONS
  Our results suggest that cortical stimulation of Broca's area elicits hemodynamic responses in Wernicke's area via cortico-cortical connectivity. We demonstrated cortico-cortical evoked responses in language systems using iNIRS during direct cortical stimulation. Our iNIRS data will provide useful information about cortico-cortical networks underlying human brain functions intraoperatively and will contribute to neurosurgical treatment in eloquent areas.
authors.affiliation: Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan. Electronic address: k-suke0412@bri.niigata-u.ac.jp.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sato
authors.affiliation: Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hiraishi
authors.affiliation: Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Takao
authors.affiliation: Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D000293:Adolescent; D000328:Adult; D065711:Broca Area / Q000502:physiology*; D002648:Child; D004558:Electric Stimulation; D004827:Epilepsy / Q000601:surgery; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007802:Language; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D065813:Wernicke Area / Q000502:physiology*
keywords: Cortico-cortical network; Direct cortical stimulation; Epilepsy surgery; Language systems; Near-infrared spectroscopy