Poster No:
1770
Submission Type:
Abstract Submission
Authors:
Riho Nakajima1, Wataru Uchida2, Kenichi Nakajima3, Koji Kamagata2, Kaito Takabayashi2, Masashi Kinoshita4, Shigeki Aoki2, Mitsutoshi Nakada5
Institutions:
1Department of Occupational Therapy, Kanazawa University, Kanazawa, Japan, 2Department of Radiology, Faculty of Medicine, Juntendo University, Tokyo, Japan, 3Department of Nuclear Medicine, Kanazawa University, Kanazawa, Japan, 4Department of Neurosurgery,Kanazawa University, Kanazawa, Japan, 5Department of Neurosurgery, Kanazawa University, Kanazawa, Japan
First Author:
Riho Nakajima
Department of Occupational Therapy, Kanazawa University
Kanazawa, Japan
Co-Author(s):
Wataru Uchida
Department of Radiology, Faculty of Medicine, Juntendo University
Tokyo, Japan
Kenichi Nakajima
Department of Nuclear Medicine, Kanazawa University
Kanazawa, Japan
Koji Kamagata
Department of Radiology, Faculty of Medicine, Juntendo University
Tokyo, Japan
Kaito Takabayashi
Department of Radiology, Faculty of Medicine, Juntendo University
Tokyo, Japan
Shigeki Aoki
Department of Radiology, Faculty of Medicine, Juntendo University
Tokyo, Japan
Introduction:
The superficial white matter (SWM) comprises a layer of white matter that forms connections near cortical sulci. Neuroimaging studies have examined the shape and localization of SWM and their functional impacts on its integrity. However, the structural connectivity of SWM networks with the cortices remains poorly understood. A previous our study identified key anatomical structures, termed "crossings," where SWM fibers converge from multiple directions, using fiber dissection analysis [1]. Therefore, we analyzed the characteristics of SWM networks based on crossings using diffusion-weighted neuroimaging data.
Methods:
Diffusion magnetic resonance imaging (MRI) data from 10 healthy individuals, sourced from the Human Connectome Project, were utilized. A total of 605 regions of interest (ROIs) were defined in the MNI152 T1-weighted image template space at presumed crossing locations. For fiber tracking, the probabilistic second-order integration over fiber orientation distributions (iFOD2) algorithm was applied to estimate streamlines (step size = 0.625 mm, maximum angle = 45°, FOD amplitude cutoff = 0.1, and number of seedings = 5 million). Streamline lengths were categorized into three groups: 5–20 mm, 21–40 mm, and 41–60 mm, representing short-, middle-, and long-length fibers, respectively. The number of streamlines connecting each pair of ROIs was modeled as a connectivity matrix. We then calculated the number of connections for each ROI and cross-tabulated these connections by brain gyrus. Furthermore, the graph theoretical measure of "local efficiency" was calculated using the connectivity matrix to evaluate network integration and segregation. Hub ROIs were defined as those with local efficiency values exceeding the mean plus one standard deviation (SD) across participants. These hub ROIs were then compared with myelin concentrations, calculated using the T1/T2 ratio [2], and cortical cellular structures based on Economo-Koskinas cytoarchitectonics [3].
Results:
The frequency of intragyral connections decreased with increasing tract length, being lowest for long-length fibers. Short-length fibers primarily connected within or between adjacent gyri, whereas long-length fibers connected both adjacent and non-adjacent gyri. Local efficiency was then calculated, and hub ROIs were identified. Hubs for short- and middle-length fibers located predominantly in primary regions, including the lateral occipital lobe, cuneus, lingual gyrus, and precentral and postcentral gyri. Hub ROIs were also present in the cingulate gyrus and basal temporal lobe, including the hippocampus and fusiform gyrus. These regions associated with motor and sensory functions, especially visual processing. In contrast, long-length fibers exhibited fewer hub ROIs in the occipital lobe and a higher concentration in association areas such as the dorsolateral prefrontal cortex and inferior parietal lobule.
An analysis of the relationship between hub regions and cytoarchitectonic classification revealed distinct patterns. For short-length fibers, Area 5 contained the highest proportion of hub ROIs (63.9%), followed by Area 4 (26.0%) and Area 1 (17.2%). For long-length fibers, Area 1 (29.0%) had the highest number of hub ROIs, followed by Area 3 (24.4%).
A significant correlation was observed between T1/T2 values, reflecting cortical and subcortical myelination, and the local efficiency index for short- and middle-length fibers (Spearman's rho = 0.55, P = 1.17 × 10-49; Spearman's rho = 0.32, P = 5.39 × 10-16, respectively). These results indicate that ROIs with higher local efficiency predominantly comprise short- and middle-length fibers with elevated myelin levels.
Conclusions:
These findings contribute to the deeper understanding of SWM network characteristics, highlighting its high-connectivity regions and providing critical insights into the anatomical structure of the brain.
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Subcortical Structures 2
White Matter Anatomy, Fiber Pathways and Connectivity 1
Novel Imaging Acquisition Methods:
Diffusion MRI
Keywords:
Cortical Layers
MRI
Myelin
Sub-Cortical
White Matter
Other - superficial white matter, graph theory
1|2Indicates the priority used for review
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Please indicate below if your study was a "resting state" or "task-activation” study.
Other
Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Healthy subjects
Was this research conducted in the United States?
No
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel?
NOTE: Any human subjects studies without IRB approval will be automatically rejected.
Yes
Were any animal research approved by the relevant IACUC or other animal research panel?
NOTE: Any animal studies without IACUC approval will be automatically rejected.
Not applicable
Please indicate which methods were used in your research:
Diffusion MRI
For human MRI, what field strength scanner do you use?
3.0T
Which processing packages did you use for your study?
FSL
Provide references using APA citation style.
1. Shinohara H, Liu X, Nakajima R, et al. Pyramid-shape crossings and intercrossing fibers are key elements for construction of the neural network in the superficial white matter of the human cerebrum. Cereb Cortex. 2020;30(10):5218–5228.
2. Glasser MF, Van Essen DC. Mapping human cortical areas in vivo based on myelin content as revealed by T1- and T2-weighted MRI. J Neurosci. 2011;31(32):11597–11616.
3. Economo C, Koskinas GN. Die Cytoarchitektonik der Hirnrinde des erwachsenen Menschen: Textband und Atlas. Springer; 1925.
No