Somatotopic organization of thalamocortical projection fibers as assessed with MR tractography.
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.
Yamada
Kei
K
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
Nagakane
Yoshinari
Y
Yoshikawa
Kenji
K
Kizu
Osamu
O
Ito
Hirotoshi
H
Kubota
Takao
T
Akazawa
Kentaro
K
Oouchi
Hiroyuki
H
Matsushima
Shigenori
S
Nakagawa
Masanori
M
Nishimura
Tsunehiko
T
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*