TY - JOUR
T1 - A gyral coordinate system predictive of fibre orientations
AU - Cottaar, Michiel
AU - Bastiani, Matteo
AU - Chen, Charles
AU - Dikranian, Krikor
AU - Van Essen, David
AU - Behrens, Timothy E.
AU - Sotiropoulos, Stamatios N.
AU - Jbabdi, Saad
N1 - Funding Information:
MC is supported by the EPSRC UK ( EP/L023067 ). MB is supported by the European Research Council under the European Union's Seventh Framework Programme ( FP/2007–2013/ ERC Grant Agreement no. 319456 ). SJ is supported by the MRC UK (Grant Ref: MR/L009013/1 ). The Wellcome Centre for Integrative Neuroimaging is supported by core funding from the Wellcome Trust ( 203139/Z/16/Z ). Primate studies were supported in part by the National Institutes of Health , Bethesda, MD, USA; grants HD052664 , HD37100 , and HD062171 ; and by DA 05072 and 8P51OD011092 for the operation of the Oregon National Primate Research Center . Appendix A
Publisher Copyright:
© 2018 Elsevier Inc.
PY - 2018/8/1
Y1 - 2018/8/1
N2 - When axonal fibres approach or leave the cortex, their trajectories tend to closely follow the cortical convolutions. To quantify this tendency, we propose a three-dimensional coordinate system based on the gyral geometry. For every voxel in the brain, we define a “radial” axis orthogonal to nearby surfaces, a “sulcal” axis along the sulcal depth gradient that preferentially points from deep white matter to the gyral crown, and a “gyral” axis aligned with the long axis of the gyrus. When compared with high-resolution, in-vivo diffusion MRI data from the Human Connectome Project, we find that in superficial white matter the apparent diffusion coefficient (at b = 1000) along the sulcal axis is on average 16% larger than along the gyral axis and twice as large as along the radial axis. This is reflected in the vast majority of observed fibre orientations lying close to the tangential plane (median angular offset < 7°), with the dominant fibre orientation typically aligning with the sulcal axis. In cortical grey matter, fibre orientations transition to a predominantly radial orientation. We quantify the width and location of this transition and find strong reproducibility in test-retest data, but also a clear dependence on the resolution of the diffusion data. The ratio of radial to tangential diffusion is fairly constant throughout most of the cortex, except for a decrease of the diffusivitiy ratio in the sulcal fundi and the primary somatosensory cortex (Brodmann area 3) and an increase in the primary motor cortex (Brodmann area 4). Although only constrained by cortical folds, the proposed gyral coordinate system provides a simple and intuitive representation of white and grey matter fibre orientations near the cortex, and may be useful for future studies of white matter development and organisation.
AB - When axonal fibres approach or leave the cortex, their trajectories tend to closely follow the cortical convolutions. To quantify this tendency, we propose a three-dimensional coordinate system based on the gyral geometry. For every voxel in the brain, we define a “radial” axis orthogonal to nearby surfaces, a “sulcal” axis along the sulcal depth gradient that preferentially points from deep white matter to the gyral crown, and a “gyral” axis aligned with the long axis of the gyrus. When compared with high-resolution, in-vivo diffusion MRI data from the Human Connectome Project, we find that in superficial white matter the apparent diffusion coefficient (at b = 1000) along the sulcal axis is on average 16% larger than along the gyral axis and twice as large as along the radial axis. This is reflected in the vast majority of observed fibre orientations lying close to the tangential plane (median angular offset < 7°), with the dominant fibre orientation typically aligning with the sulcal axis. In cortical grey matter, fibre orientations transition to a predominantly radial orientation. We quantify the width and location of this transition and find strong reproducibility in test-retest data, but also a clear dependence on the resolution of the diffusion data. The ratio of radial to tangential diffusion is fairly constant throughout most of the cortex, except for a decrease of the diffusivitiy ratio in the sulcal fundi and the primary somatosensory cortex (Brodmann area 3) and an increase in the primary motor cortex (Brodmann area 4). Although only constrained by cortical folds, the proposed gyral coordinate system provides a simple and intuitive representation of white and grey matter fibre orientations near the cortex, and may be useful for future studies of white matter development and organisation.
UR - http://www.scopus.com/inward/record.url?scp=85047018611&partnerID=8YFLogxK
U2 - 10.1016/j.neuroimage.2018.04.040
DO - 10.1016/j.neuroimage.2018.04.040
M3 - Article
C2 - 29684644
AN - SCOPUS:85047018611
SN - 1053-8119
VL - 176
SP - 417
EP - 430
JO - NeuroImage
JF - NeuroImage
ER -