Myelination selectively modulates BOLD signal characteristics in white matter: from myelin content to gene expression

Motivation: Factors affecting BOLD signals in white matter (WM) have not been elucidated. Goal(s): Identify potential relationships of BOLD signal with myelination in white matter. Approach: HCP and brain atlas data used to measure correlations of BOLD fALFF with cerebral blood volume (CBV), myelin water fraction (MWF) and myelin basic protein (MBP) gene expression across association and projection WM bundles. Results: 1) fALFF positively correlated with CBV, but projection bundles had lower fALFF for equivalent venous CBV; (2) fALFF positively correlated with MWF in association bundles, with no significant correlation in projection bundles; (3) fALFF negatively correlated with MBP gene expression. Impact: This study demonstrates a heterogeneous dependence of white matter functional signals on myelin, supported by both in-vivo MRI evidence and gene expression data, while confirming a strong effect of vascular density on BOLD effects