Cross-population myelination covariance of human cerebral cortex

Abstract

Cross-population covariance of brain morphometric quantities provides a measure of inter-areal connectivity, as it is believed to be determined by the coordinated neurodevelopment of connected brain regions. Although useful, structural covariance analysis predominantly employed bulky morphological measures with mixed compartments, whereas studies of the structural covariance of any specific subdivisions like myelin are rare. Characterizing myelination covariance is of interest, as it will reveal connectivity patterns determined by coordinated development of myeloarchitecture between brain regions. Using myelin content MRI maps from the Human Connectome Project, here we showed that the cortical myelination covariance was highly reproducible, and exhibited a brain organization similar to that previously revealed by other connectivity measures. Additionally, the myelination covariance network shared common topological features of human brain networks like small worldness. Furthermore, we found that the correlation between myelination covariance and resting-state functional connectivity (RSFC) was uniform within each resting-state network (RSN), but could considerably vary between RSNs. Interestingly, this myelination covariance-RSFC correlation was appreciably stronger in sensory and motor networks than cognitive and poly-modal association networks, possibly due to their different circuitry structures. This study has established a new brain connectivity measure specifically related to axons, and this measure can be valuable to investigating coordinated myeloarchitecture development.

Depth‐dependent abnormal cortical myelination in first‐episode treatment‐naïve schizophrenia

“…Glasser and colleagues reported that T1‐weighted (T1w)/T2‐weighted (T2w) ratio value could reflect cortical myelination (Glasser & Van Essen, ). Evidence shows that this method can precisely estimate cortical myelination: (a) Virtual boundaries of brain regions generated based on T1w/T2w ratio were well aligned with results in prior anatomical and functional brain study (Glasser & Van Essen, ); (b) T1w/T2w ratio had similar cortical distribution compared to signal density pattern in neurite imaging (Fukutomi et al, ); (c) abnormal myelination of WM revealed by this method was highly consistent with the DTI results in patients with multiple sclerosis (Nakamura, Chen, Ontaneda, Fox, & Trapp, ); (d) structural covariance networks generated based on T1w/T2w ratio corresponded to functional brain network (Ma & Zhang, ). Hagiwara et al also demonstrated that the correspondence between T1w/T2w ratio and myelin water fraction was strong across the gray matter (Hagiwara et al, ).…”

Myelin Measurement: Comparison Between Simultaneous Tissue Relaxometry, Magnetization Transfer Saturation Index, and T1w/T2w Ratio Methods

“…T 1 w/T 2 w ratio is another approach for assessing myelin content in the cortical gray matter, originally developed to map myeloarchitecturally distinct cortical regions for parcellation of cerebral cortex, thus providing a connectivity measurement 33 , 34 . Pixel intensity on T 1 w and T 2 w images is assumed to be directly and inversely proportional to myelin contrast, respectively.…”

The developing relations between networks of cortical myelin and neurophysiological connectivity

“…The use of T1-w/T2-w ratio in measuring structural covariance has been shown to produce brain organization similar to that of other structural measures and is validated as reproducible in adults and children (21,22). Our data support the use of T1-w/T2-w ratio to measure myelin covariance -our structural covariance networks demonstrated organization as well as high and symmetric intra-hemispheric connectivity in both children and adults, consistent with our previous study using MT (15).…”

“…An alternative approach is to take the ratio of two commonly acquired images, T1-weighted (T1-w) and T2-weighted (T2-w) to form a voxel-wise map of myelin estimates (17)(18)(19)(20). The concordance between MT and the T1-w/T2-w ratio appears to be high in both the white and grey matter (21), and has been shown as a valid and reproducible measure to use when examining structural covariance (22) . Moreover, as the two elements required for this technique are often routinely acquired, there are opportunities for retrospective analyses of large datasets.…”