title: Association fibers connecting the Broca center and the lateral superior frontal gyrus: a microsurgical and tractographic anatomy.
abstract: OBJECTIVE
  Recently, intraoperative mapping has disclosed that, in addition to the classic language centers (that is, the Broca and Wernicke centers), other cortical regions may also play an important role in language organization. In the prefrontal cortex, although the lateral superior frontal gyrus (LSFG) could have language-related functions, there are no detailed reports that demonstrate the anatomical connection between the LSFG and other well-known language cortices, such as the Broca center. To show the existence of the structural connection, white matter association fibers between the inferior frontal gyrus (IFG) and the LSFG were examined using fiber dissection (FD) and diffusion tensor (DT) imaging-based tractography.
  
  
  METHODS
  Eight cadaveric cerebral hemispheres were dissected to reveal the association fibers between the IFG and LSFG. The DT imaging-based tractography studies targeting the prefrontal cortex were obtained in 53 right-handed patients who had no organic cerebral lesions.
  
  
  RESULTS
  The association fiber tract between Brodmann area 44/45 (the Broca center in the dominant hemisphere) and LSFG were detected in all specimens by FD. In the DT imaging-based tractography studies, the tract was identified in all patients bilaterally, except for the 4 in whom the tract was detected only in the left hemisphere. This tract was spread significantly wider in the left than in the right hemisphere, and left lateralization was evident in male patients.
  
  
  CONCLUSIONS
  Based on its character, this tract was named the Broca-LSFG pathway. These findings suggest a close relationship between this pathway and language organization. The structural anatomy of the Broca-LSFG pathway may explain speech disturbances induced by LSFG stimulation that are sometimes observed during intraoperative language mapping.
authors.affiliation: Departments of Neurosurgery, Kanazawa University, Kanazawa, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Harumichi
authors.initials: H
authors.lastname: Shinohara
authors.forename: Osamu
authors.initials: O
authors.lastname: Hori
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ozaki
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Ueda
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Nakada
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Hamada
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hayashi
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D002102:Cadaver; D056324:Diffusion Tensor Imaging; D004210:Dissection / Q000379:methods; D004292:Dominance, Cerebral; D005260:Female; D005625:Frontal Lobe / Q000166:cytology*; D006801:Humans; D008297:Male; D008866:Microsurgery / Q000379:methods; D008875:Middle Aged; D009434:Neural Pathways / Q000166:cytology*; D017397:Prefrontal Cortex / Q000166:cytology*; D013060:Speech