Layer-specific variation of iron content in cerebral cortex as a source of MRI contrast

TLDR

High‑field MRI now reveals strong contrast variations in cortical gray matter that likely reflect laminar architecture and subtle differences in magnetic properties such as iron and myelin content. The study seeks to identify the source of cortical MRI contrast by comparing postmortem MRI data with electron microscopy and histological iron and myelin staining. MRI data from postmortem brain samples were compared with electron microscopy and histological staining for iron and myelin. Iron is distributed across cortical laminae in a pattern that mirrors regional myeloarchitecture and constitutes the dominant source of the observed MRI contrast.

Abstract

Recent advances in high-field MRI have dramatically improved the visualization of human brain anatomy in vivo. Most notably, in cortical gray matter, strong contrast variations have been observed that appear to reflect the local laminar architecture. This contrast has been attributed to subtle variations in the magnetic properties of brain tissue, possibly reflecting varying iron and myelin content. To establish the origin of this contrast, MRI data from postmortem brain samples were compared with electron microscopy and histological staining for iron and myelin. The results show that iron is distributed over laminae in a pattern that is suggestive of each region’s myeloarchitecture and forms the dominant source of the observed MRI contrast.