title: Somatotopic organization of thalamocortical projection fibers as assessed with MR tractography.
abstract: OBJECTIVE
  To prospectively evaluate the course of sensory fibers through the supratentorial brain with diffusion-tensor-based tractography.
  
  
  METHODS
  This study was approved by the institutional review board. Informed consent was obtained. Seven healthy volunteers (five men, two women; age range, 20-55 years) underwent 1.5-T magnetic resonance imaging. Diffusion-tensor images with isotropic voxels (2 x 2 x 2 mm) were obtained by using a single-shot echo-planar imaging technique, with a motion-probing gradient in 15 orientations, a b value of 1000 sec/mm(2), and nine signals acquired. The total imaging time was approximately 30 minutes. Fiber tracking of the sensorimotor pathways was performed with the fiber assignment by continuous tracking method.
  
  
  RESULTS
  All the pyramidal tracts rotated anteriorly as they traveled through the centrum semiovale. On the other hand, the sensory tracts rotated posteriorly as they coursed through the centrum semiovale toward the cortex. When the sensorimotor tracts were viewed as a unit, the tracts of the lower extremity formed the axis of rotation around which the other parts of the pyramidal and sensory homunculus rotated.
  
  
  CONCLUSIONS
  Sensorimotor fibers of the lower extremity form an axis of rotation, around which the pyramidal fibers rotate anteriorly and the sensory fibers rotate posteriorly.
authors.affiliation: Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kajii-cyo, Kawaramachi Hirokoji Sagaru, Kamigyo-ku, Kyoto City, Kyoto 602-8566, Japan. kyamada@koto.kpu-m.ac.jp
authors.forename: Kei
authors.initials: K
authors.lastname: Yamada
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Nagakane
authors.forename: Kenji
authors.initials: K
authors.lastname: Yoshikawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Kizu
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Ito
authors.forename: Takao
authors.initials: T
authors.lastname: Kubota
authors.forename: Kentaro
authors.initials: K
authors.lastname: Akazawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oouchi
authors.forename: Shigenori
authors.initials: S
authors.lastname: Matsushima
authors.forename: Masanori
authors.initials: M
authors.lastname: Nakagawa
authors.forename: Tsunehiko
authors.initials: T
authors.lastname: Nishimura
mesh_terms: D000293:Adolescent; D000328:Adult; D000344:Afferent Pathways / Q000166:cytology*; D002540:Cerebral Cortex / Q000166:cytology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D013788:Thalamus / Q000166:cytology*