RT Journal Article
SR Electronic
T1 Diffusion MRI Anisotropy in the Cerebral Cortex is Determined by Unmyelinated Tissue Features
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.09.02.458694
DO 10.1101/2021.09.02.458694
A1 Reveley, Colin
A1 Ye, Frank Q
A1 Mars, Rogier B
A1 Matrov, Denis
A1 Chudasama, Yogita
A1 Leopold, David A
YR 2022
UL http://biorxiv.org/content/early/2022/06/22/2021.09.02.458694.abstract
AB Diffusion magnetic resonance imaging (dMRI) is commonly used to assess the tissue and cellular substructure of the human brain. In the white matter, myelinated axons are the principal neural elements that shape dMRI through the restriction of water diffusion; however, in the gray matter the relative contributions of myelinated axons and other tissue features to dMRI are poorly understood. Here we investigate the determinants of diffusion in the cerebral cortex. Specifically, we ask whether myelinated axons significantly shape dMRI fractional anisotropy (dMRI-FA), a measure commonly used to characterize tissue properties in humans. We compared ultra-high resolution ex vivo dMRI data from the brain of a marmoset monkey with both myelin- and Nissl-stained histological sections obtained from the same brain after scanning. We found that cortical diffusion was only minimally related to the density and arrangement of myelinated fibers. Instead, the spatial pattern of dMRI-FA in the cortex was more closely related to anisotropy of tissue features indicated in the Nissl stained sections. Our results suggest that unmyelinated neurites such as large caliber apical dendrites are the primary features shaping dMRI measures in the cerebral cortex.Competing Interest StatementThe authors have declared no competing interest.