Connectivity-Based Topographical Changes of the Corpus Callosum During Aging

Yuchen Liu; Chih-Chin Heather Hsu; Chu-Chung Huang; Yajuan Zhang; Jiajia Zhao; Shih-Jen Tsai; Liang-Kung Chen; Ching-Po Lin; Chun-Yi Zac Lo

doi:10.3389/fnagi.2021.753236

Connectivity-Based Topographical Changes of the Corpus Callosum During Aging

Front Aging Neurosci. 2021 Oct 20:13:753236. doi: 10.3389/fnagi.2021.753236. eCollection 2021.

Authors

Yuchen Liu¹, Chih-Chin Heather Hsu^{2

3}, Chu-Chung Huang^{4

5}, Yajuan Zhang¹, Jiajia Zhao¹, Shih-Jen Tsai^{6

7

8}, Liang-Kung Chen^{3

9

10}, Ching-Po Lin^{1

2

9}, Chun-Yi Zac Lo¹

Affiliations

¹ Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China.
² Institute of Neuroscience, National Yang Ming Chiao Tung University, Taipei, Taiwan.
³ Center of Geriatrics and Gerontology, Taipei Veterans General Hospital, Taipei, Taiwan.
⁴ Shanghai Key Laboratory of Brain Functional Genomics (Ministry of Education), Affiliated Mental Health Center (ECNU), School of Psychology and Cognitive Science, East China Normal University, Shanghai, China.
⁵ Shanghai Changning Mental Health Center, Shanghai, China.
⁶ Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan.
⁷ Division of Psychiatry, Faculty of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
⁸ Institute of Brain Science, National Yang Ming Chiao Tung University, Taipei, Taiwan.
⁹ Aging and Health Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan.
¹⁰ Taipei Municipal Gan-Dau Hospital, Taipei, Taiwan.

Abstract

Background: The corpus callosum (CC) is the most prominent white matter connection for interhemispheric information transfer. It is implicated in a variety of cognitive functions, which tend to decline with age. The region-specific projections of the fiber bundles with microstructural heterogeneity of the CC are associated with cognitive functions and diseases. However, how the CC is associated with the information transfer within functional networks and the connectivity changes during aging remain unclear. Studying the CC topography helps to understand the functional specialization and age-related changes of CC subregions. Methods: Diffusion tractography was used to subdivide the CC into seven subregions from 1,086 healthy volunteers within a wide age range (21-90 years), based on the connections to the cortical parcellations of the functional networks. Quantitative diffusion indices and connection probability were calculated to study the microstructure differences and age-related changes in the CC subregions. Results: According to the population-based probabilistic topography of the CC, part of the default mode network (DMN) and limbic network (LN) projected fibers through the genu and rostrum; the frontoparietal network (FPN), ventral attention network (VA) and somatomotor networks (SM) were interconnected by the CC body; callosal fibers arising from the part of the default mode network (DMN), dorsal attention network (DA) and visual network (VIS) passed through the splenium. Anterior CC subregions interconnecting DMN, LN, FPN, VA, and SM showed lower fractional anisotropy (FA) and higher mean diffusivity (MD) and radial diffusivity (RD) than posterior CC subregions interconnecting DA and VIS. All the CC subregions showed slightly increasing FA and decreasing MD, RD, and axial diffusivity (AD) at younger ages and opposite trends at older ages. Besides, the anterior CC subregions exhibited larger microstructural and connectivity changes compared with the posterior CC subregions during aging. Conclusion: This study revealed the callosal subregions related to functional networks and uncovered an overall "anterior-to-posterior" region-specific changing trend during aging, which provides a baseline to identify the presence and timing of callosal connection states.

Keywords: aging trajectory; atlas; diffusion MRI; functional networks; segmentation; tractography.