Subdividing the superior longitudinal fasciculus using local quantitative MRI.

Area of Science:

• Neuroscience
• Neuroimaging
• Human Brain Anatomy

Background:

• The superior longitudinal fasciculus (SLF) is crucial for connecting frontal and parietal cortical regions.
• Current in vivo studies often treat the SLF as a single entity, overlooking its distinct sub-bundles.
• The SLF comprises three sub-bundles (SLF-I, SLF-II, SLF-III) with unique trajectories and functions.

Purpose of the Study:

• To develop and validate a data-driven method for separating SLF-III from other SLF sub-bundles using MRI microstructure parameters.
• To demonstrate the reproducibility of the proposed separation technique across independent datasets and tractography algorithms.

Main Methods:

• Utilized diffusion MRI (fractional anisotropy) and relaxometry-based parameters (T1, T2, T2*, T2w/T1w).
• Applied a data-driven approach based on microstructure measurements for SLF-III separation.
• Tested the procedure on three independent datasets and multiple tractography algorithms.

Main Results:

• Successfully separated SLF-III from the rest of the SLF complex using the proposed microstructure-based method.
• Demonstrated the reproducibility of the separation procedure across different datasets and tractography techniques.
• Identified differential crossing with other white matter tracts as a potential source for distinct MRI signatures of SLF-II and SLF-III.

Conclusions:

• The proposed method effectively distinguishes SLF-III based on its unique MRI signatures.
• This approach advances the study of brain connectivity by enabling the analysis of individual SLF sub-bundles.
• Understanding the distinct microstructural properties of SLF sub-bundles is crucial for accurate tractography and functional interpretation.