Neurite imaging reveals microstructural variations in human cerebral cortical gray matter

Abstract

We present distinct patterns of neurite distribution in the human cerebral cortex using diffusion magnetic resonance imaging (MRI). We analyzed both high-resolution structural (T1w and T2w images) and diffusion MRI data in 505 subjects from the Human Connectome Project. Neurite distributions were evaluated using the neurite orientation dispersion and density imaging (NODDI) model, optimized for gray matter, and mapped onto the cortical surface using a method weighted towards the cortical mid-thickness to reduce partial volume effects. The estimated neurite density was high in both somatosensory and motor areas, early visual and auditory areas, and middle temporal area (MT), showing a strikingly similar distribution to myelin maps estimated from the T1w/T2w ratio. The estimated neurite orientation dispersion was particularly high in early sensory areas, which are known for dense tangential fibers and are classified as granular cortex by classical anatomists. Spatial gradients of these cortical neurite properties revealed transitions that colocalize with some areal boundaries in a recent multi-modal parcellation of the human cerebral cortex, providing mutually supportive evidence. Our findings indicate that analyzing the cortical gray matter neurite morphology using diffusion MRI and NODDI provides valuable information regarding cortical microstructure that is related to but complementary to myeloarchitecture.

Neurocognitive and psychiatric disorders‐related axonal degeneration in Parkinson's disease

“…MD was shown to be more accurate than FA (Wiltshire et al, ), and a recent investigation in patients with premanifest Huntington's disease using NODDI also showed widespread reduction in ICVF that overlapped with increased MD (Zhang et al, ). A strong negative correlation has been demonstrated between the ICVF and MD maps in the human brain (Fukutomi et al, ). On the contrary, other DTI indices have been shown to be inconsistent.…”

“…that overlapped with increased MD . A strong negative correlation has been demonstrated between the ICVF and MD maps in the human brain (Fukutomi et al, 2018). On the contrary, other DTI indices have been shown to be inconsistent.…”

Effects ofSYN1Q555Xmutation on cortical gray matter microstructure

“…For example, changes in compartments permeability, cell shape or cell population sizes, could affect the diffusion measures in a non‐trivial manner, affecting MD/ISOVF more than MK/ICVF in this particular situation. Another interesting possibility is that MK/ICVF could be mostly representative of myelinated axons (Fukutomi et al, ), thus suggesting an increase only in unmyelinated dendrites density in the SYN1 Q555x population. It is also plausible that the behavior of MK/ICVF differs between the gray matter and the white matter, and thus that its interpretation may not be directly transferable from what is known in the white matter to the gray matter, where its properties are not as well established.…”

Optimizing the fitting initial condition for the parallel intrinsic diffusivity in NODDI: An extensive empirical evaluation

“…Results suggested 66 that the default value was reasonable in white matter, but it was sub-optimal in gray matter. 67 While recent publications have found our method useful [26,27], this earlier work only 68 considered a single axial slice from three age matched participants and dMRI data acquired 69 with the same imaging protocol. For this reason, we propose a more extensive implementation 70 of our method for optimizing the intrinsic diffusivity that considers a diverse array of data in 71 terms of age populations, imaging protocols, and is conducted across the full brain.…”