A Systematic Relationship Between Functional Connectivity and Intracortical Myelin in the Human Cerebral Cortex

Abstract

Research in the macaque monkey suggests that cortical areas with similar microstructure are more likely to be connected. Here, we examine this link in the human cerebral cortex using 2 magnetic resonance imaging (MRI) measures: quantitative T1 maps, which are sensitive to intracortical myelin content and provide an in vivo proxy for cortical microstructure, and resting-state functional connectivity. Using ultrahigh-resolution MRI at 7 T and dedicated image processing tools, we demonstrate a systematic relationship between T1-based intracortical myelin content and functional connectivity. This effect is independent of the proximity of areas. We employ nonlinear dimensionality reduction to characterize connectivity components and identify specific aspects of functional connectivity that are linked to myelin content. Our results reveal a consistent spatial pattern throughout different analytic approaches. While functional connectivity and myelin content are closely linked in unimodal areas, the correspondence is lower in transmodal areas, especially in posteromedial cortex and the angular gyrus. Our findings are in agreement with comprehensive reports linking histologically assessed microstructure and connectivity in different mammalian species and extend them to the human cerebral cortex in vivo.

Biophysical Modeling of Large-Scale Brain Dynamics and Applications for Computational Psychiatry

“…The authors found that the T1w/T2w–derived map indeed yielded substantially improved fits compared with randomized surrogate heterogeneity maps. These findings identify the T1w/T2w map as a preferential axis for heterogeneity shaping FC (102,103). More broadly, this study provides a useful path forward in hypothesis-driven whole-brain modeling by using the topography of a heterogeneity map to parametrize local circuit properties across brain areas.…”

Large-Scale Gradients in Human Cortical Organization

“…A similar spatial distribution has been described for MRI-based measures of cortical thickness [12] and myelinated thickness [29]. Cortical thickness coarsely tracks changes in cytoarchitecture [30] and myelin content [25], and can be viewed as a pragmatic surrogate for cortical microstructure [12].…”

“…In addition, the spatial layout of the principal gradient aligns with the human microstructural gradient described in the previous section. A direct comparison of the principal gradient of functional connectivity and intracortical myelin content revealed a systematic spatial relationship [25]. Global connectivity patterns thus reveal a sensorimotor-to-transmodal gradient that is strongly related to a gradient in local microstructural features and the intrinsic geometry of the cortex.…”

“…For example, MRI measures that are sensitive to intracortical myelin have revealed a pattern of high myelin content in primary sensorimotor regions, which systematically decreases toward transmodal areas in parietal, temporal, and particularly prefrontal cortex [3,[25][26][27][28] (Figure 1A). A similar spatial distribution has been described for MRI-based measures of cortical thickness [12] and myelinated thickness [29].…”

“…For example, decomposition of primary visual cortex functional connectivity yields two dominant gradients, each reflecting a different aspect of retinotopic organization -eccentricity and polar angle [37]. Other times, the spatial distribution of different superimposed gradients is less obviously related to known anatomical or functional properties and their interpretation can be more challenging [25].…”