Dataset Information

Connectivity-Based Topographical Changes of the Corpus Callosum During Aging.

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.

SUBMITTER: Liu Y

PROVIDER: S-EPMC8565522 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Connectivity-Based Topographical Changes of the Corpus Callosum During Aging.

Liu Yuchen Y Hsu Chih-Chin Heather CH Huang Chu-Chung CC Zhang Yajuan Y Zhao Jiajia J Tsai Shih-Jen SJ Chen Liang-Kung LK Lin Ching-Po CP Lo Chun-Yi Zac CZ

Frontiers in aging neuroscience 20211020

<b>Background:</b> 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 ag ...[more]

PMID: 34744693

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Project description:The Corpus Callosum (CC) is an important structure that includes the majority of fibers connecting the two brain hemispheres. Several neurodegenerative diseases may alter CC size and morphology leading to its atrophy and malfunction which may play a role in the pathological manifestations found in these diseases. The purpose of the current study is to determine any possible changes in CC size in patients suffering from Alzheimer's disease. The Study also investigated the effect of acetylcholinesterase inhibitors (AChEIs) on the size of CC and its association with improvement in the Alzheimer disease severity scores. Midsagittal size of CC were recorded prospectively from 439 routine T1-weighted MRI brain images in normal individuals. The internal skull surface was measured to calculate CC/ internal skull surface ratio. Two groups of patients were studied: 300 (150 male / 150 female) were healthy subjects and 130 (55 males / 75 females) had Alzheimer disease. Out of the 130 Alzheimer disease pateints, 70 patients were treated with Donepezil or Rivastigmine or both. The size of the CC was measured based on T1-weighted MRI images after the treatment to investigate any possible improvement in CC size. The mean surface area of CC in controls was 6.53±1.105 cm2. There was no significant difference between males and females (P < 0.627), and CC/ internal skull surface ratio was 4.41±0.77%. Patients with mild or severe Alzheimer disease showed a significant reduction in CC size compared to healthy controls. Treating mild Alzheimer patients with either Donepezil or Rivastigmine exerts a comparable therapeutic effect in improving the CC size. There was more improvement in the size of CC in patients with severe Alzheimer disease by using combined therapy of Donepezil and Rivastigmine than using single a medication. we measured the mean size of the various portions of the corpus callosum in normal individuals and Alzheimer patients before and after taking Donepezil and Rivastigmine. Alzheimer patients have pronounced reduction in CC which is corrected after taking Donepezil and Rivastigmine leading to remarkable improvement in Alzheimer disease severity scores.

Project description:IntroductionFetal alcohol spectrum disorders (FASD) range from fetal alcohol syndrome (FAS) to non-syndromic non-specific forms (NS-FASD) that are still underdiagnosed and could benefit from new neuroanatomical markers. The main neuroanatomical manifestation of prenatal alcohol exposure on developmental toxicity is the reduction in brain size, but repeated imaging observations have long driven the attention on the corpus callosum (CC), without being all convergent. Our study proposed a new segmentation of the CC that relies on both a sulci-based cortical segmentation and the "hemispherotopic" organization of the transcallosal fibers.MethodsWe collected a monocentric series of 37 subjects with FAS, 28 with NS-FASD, and 38 with typical development (6 to 25 years old) using brain MRI (1.5T). Associating T1- and diffusion-weighted imaging, we projected a sulci-based cortical segmentation of the hemispheres on the midsagittal section of the CC, resulting in seven homologous anterior-posterior parcels (frontopolar, anterior and posterior prefrontal, precentral, postcentral, parietal, and occipital). We measured the effect of FASD on the area of callosal and cortical parcels by considering age, sex, and brain size as linear covariates. The surface proportion of the corresponding cortical parcel was introduced as an additional covariate. We performed a normative analysis to identify subjects with an abnormally small parcel.ResultsAll callosal and cortical parcels were smaller in the FASD group compared with controls. When accounting for age, sex, and brain size, only the postcentral (η2 = 6.5%, pFDR = 0.032) callosal parcel and % of the cortical parcel (η2 = 8.9%, pFDR = 0.007) were still smaller. Adding the surface proportion (%) of the corresponding cortical parcel to the model, only the occipital parcel was persistently reduced in the FASD group (η2 = 5.7%, pFDR = 0.014). In the normative analysis, we found an excess of subjects with FASD with abnormally small precentral and postcentral (peri-isthmic) and posterior-splenial parcels (pFDR < 0.05).ConclusionThe objective sulcal and connectivity-based method of CC parcellation proved to be useful not only in confirming posterior-splenial damage in FASD but also in the narrowing of the peri-isthmic region strongly associated with a specific size reduction in the corresponding postcentral cortical region (postcentral gyrus). The normative analysis showed that this type of callosal segmentation could provide a clinically relevant neuroanatomical endophenotype, even in NS-FASD.

Project description:BackgroundAccumulating evidence indicates maladaptive neural information interactions between different brain regions underlie bulimia nervosa (BN). However, little is known about the alterations in interhemispheric communication of BN, which is facilitated by the corpus callosum (CC), the major commissural fiber connecting the two hemispheres. To shed light on the interhemispheric communications in BN, the present study aims to explore alterations of interhemispheric homotopic functional connectivity and the CC microstructure in BN.MethodsBased on magnetic resonance imaging (MRI) data collected from 42 BN patients and 38 healthy controls (HCs), the group differences of voxel-mirrored homotopic connectivity (VMHC) index and CC white matter microstructure were compared. Then brain regions with significant group differences in VMHC were selected as seeds for subsequent functional connectivity (FC) analysis. Seed-based fiber tracking and correlation analysis were used to analyze the relationship between VMHC and CC changes. And correlation analysis was used to reveal the correlation between abnormal imaging variables and the clinical features of BN.ResultsCompared with HCs, the BN group showed decreased fractional anisotropy (FA) in middle part of CC (CCMid) and increased VMHC in bilateral orbitofrontal cortex (OFC) and middle temporal gyrus (MTG) [false discovery rate (FDR) correction with a corrected threshold of P<0.05]. Subsequent FC analyses indicated increased FC between left OFC and right OFC, bilateral MTG, left middle occipital gyrus and right precuneus (PCUN); between right OFC and left cerebellum crus II and right PCUN; and between left MTG and right inferior temporal gyrus, right cerebellum lobule VI and right medial superior frontal gyrus (FDR correction with a corrected threshold of P<0.05). The VMHC values of OFC and MTG showed no correlations with FA values of the CCMid and the white fibers between the bilateral OFC and MTG were not through the CCMid. In addition, several regions with abnormal FC had a potential correlation trend with abnormal eating behaviors in BN patients (P<0.05, uncorrected).ConclusionsAberrant interhemispheric homotopic functional connectivity and CC microstructure were observed in BN, and they may be independent of each other. Regions with aberrant interhemispheric homotopic functional connectivity showed hyperconnectivity with regions related to reward processing, body shape perception, and self-reference.

Dataset Information

Connectivity-Based Topographical Changes of the Corpus Callosum During Aging.

Publications

Connectivity-Based Topographical Changes of the Corpus Callosum During Aging.

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