Visualizing cortical laminar architecture in the living human brain using next-generation ultra-high-gradient diffusion MRI

TL;DR

This study uses advanced MRI to visualize the layered structure of the human brain's cortex, revealing patterns of cell and nerve density that match historical tissue samples.

Contribution

The paper introduces a non-invasive method using ultra-high-gradient diffusion MRI to map cortical laminar architecture in living humans.

Findings

Intra-soma signal fraction peaks at ~55% cortical depth, matching histological patterns.

Visual cortex has higher intra-soma signal than motor cortex in deeper layers.

Intra-soma signal correlates with cortical curvature in a layer-specific manner.

Abstract

Characterizing cortical laminar microstructure is essential for understanding human brain function. Leveraging the next-generation Connectome MRI scanner (maximum gradient strength = 500mT/m, slew rate = 600T/m/s), we characterized in vivo cortical laminar cytoarchitecture and myeloarchitecture through cortical depth-dependent analyses of soma and neurite density imaging (SANDI) metrics derived from diffusion MRI, enhanced by a super-resolution technique. SANDI revealed distinct laminar profiles: intra-soma signal fraction fis peaked at ~ 55% cortical depth, while intra-neurite signal fraction fin increased toward deeper layers, consistent with histological patterns. The visual cortex exhibited higher intra-soma signal fraction fis than the motor cortex, particularly in deeper layers. Moreover, intra-soma signal fraction fis correlated positively with cortical curvature in superficial layers and negatively in deeper layers, indicating layer-specific relationships between microstructure and cortical geometry. These findings demonstrate the feasibility of noninvasively mapping cortical laminar architecture, offering a potential surrogate for histology and enabling future studies of normative and pathological brain organization using commercially available high-performance gradient MRI systems.

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