Browsing by Author "Cha, Woo-Jin"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Aging, beta‐amyloid deposition, and brain functional connectivity decline
    (Wiley, 2025-01-09) Yi, Dahyun; Chumin, Evgeny J.; Byun, Min Soo; Cha, Woo-Jin; Ahn, Hyejin; Kim, Yu Kyeong; Kang, Koung Mi; Sohn, Chul-Ho; Risacher, Shannon L.; Sporns, Olaf; Nho, Kwangsik; Saykin, Andrew J.; Lee, Dong Young; KBASE; Radiology and Imaging Sciences, School of Medicine
    Background: Changes in brain network organization are influenced by aging. Accumulation of amyloid‐beta (Aβ) and neurodegeneration in the neocortex are also expected to alter neuronal networks. Therefore, we examined the relationship between aging and brain functional connectivity (FC), as well as the effect of brain Aβ on this relationship. Method: Resting state functional MRI (rsfMRI) from 594 participants spanning age and diagnostic severity of AD from the Korean Brain Aging Study for the Early Diagnosis and Prediction of AD (KBASE) was preprocessed as previously described in studies conducted at the Indiana AD Research Center (Chumin 2021, 2023). Cortical FC data from 200 regions (Schaefer 2018) grouped into 7 canonical resting state networks (RSN; Yeo 2011) was used to compute a network segregation measure (ratio of within‐ to between‐network connectivity (Chan 2014); here used as an index of FC) across all RSNs. Additionally, a subsample of older participants was classified as Aβ positive or negative based on global amyloid in Centiloid units (Klunk 2015). Result: Intrinsic network connectivity was reduced with increasing age beginning in young adulthood (Fig, left), resulting in a dedifferentiated, or less segregated, network architecture (t = ‐4.79, p = 0.000002). The relationship between age and network segregation was significant in the Aβ negative group (t = ‐4.09, p = 0.00005); however, such relationship was not found in the Aβ positive group (Fig, right). Fitted Aβ values were significantly different (Welch Two Sample t‐test: p < 2.2e‐16). Conclusion: This preliminary study elucidates age‐related decline of brain FC, quantified as network segregation, from young adulthood to late‐life, wherein RSN communication become less coherent, manifesting as a degeneration of FC structure. Such age‐related reduction pattern of brain connectivity appears disappear under the presence of pathological Aβ deposition in brain.
  • Thumbnail Image
    Item
    Association between brain tau deposition and default mode network connectivity in cognitively normal older adults
    (Wiley, 2025-01-09) Cha, Woo-Jin; Yi, Dahyun; Chumin, Evgeny J.; Byun, Min Soo; Jung, Joon Hyung; Ahn, Hyejin; Kim, Yu Kyeong; Lee, Yun-Sang; Kang, Koung Mi; Sohn, Chul-Ho; Risacher, Shannon L.; Sporns, Olaf; Nho, Kwangsik; Saykin, Andrew J.; Lee, Dong Young; KBASE Research Group; Radiology and Imaging Sciences, School of Medicine
    Background: Alzheimer’s disease (AD) pathology occurs in the brain before manifestation of significant cognitive decline. Growing evidence suggests that brain networks such as default mode network (DMN) or salience network, identified through resting‐state functional magnetic resonance imaging (MRI), are affected by AD pathology. In this study, we investigated the relationship between network segregation and the key in vivo AD pathologies including beta‐amyloid (Aβ) and tau deposition in old adults with no cognitive impairment. Method: A total 283 older adults with normal cognition aging from 55 to 87 were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE) cohort. The participants underwent comprehensive clinical and neuropsychological assessment, [11C] Pittsburgh Compound B PET for measuring Aβ deposition, [18F] AV‐1451 PET for measuring tau deposition, structural MRI, and resting‐state functional MRI for measuring functional connectivity (FC). For PET scans, standard uptake value ratio (SUVR) was used for the analyses; combined regions of inferior cerebellum and pons were used as the reference region when obtaining SUVRs. For FC, segregation values (ratios between median z‐transformed Pearson correlation of within‐ and between‐network connectivity) for overall and the seven individual resting state networks were computed (Table). The relationships between Aβ or tau deposition and network connectivity segregation were examined through cross‐sectional approach using multiple regression analyses. In the analyses, Aβ or tau deposition was used as an independent variable and segregation values of the networks were used as dependent variables. Result: Tau deposition had a significant negative association with the DMN segregation (β = ‐0.249, p = 0.007); but, tau had no relationships with any other networks (Table). Aβ deposition was not associated with any segregation values for the seven brain networks (Table). Conclusion: Our finding suggests that impaired functional connectivity of DMN is closely linked to tau deposition even in cognitively unimpaired older individuals.