Browsing by Author "Lin, Ching-Po"

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Aging, cognition, and the brain: effects of age-related variation in white matter integrity on neuropsychological function
(2019-07-03)
Fan, Yang-Teng
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Fang, Ya-Wen
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Chen, Ya-Ping
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Leshikar, Eric D.
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Lin, Ching-Po
Alterations in brain structure are viewed as neurobiological indicators which are closely tied to cognitive changes in healthy human aging. The current study used diffusion tensor imaging (DTI) tractography to investigate the relationship between age, brain variation in white matter (WM) integrity, and cognitive function. Sixteen younger adults (aged 20-28 years) and 18 healthy older adults (aged 60-75 years) underwent DTI scanning and a standardized battery of neuropsychological measures. Behaviorally, older adults exhibited poorer performance on multiple cognitive measures compared to younger adults. At the neural level, the effects of aging on theWM integrity were evident within interhemispheric (the anterior portion of corpus callosum) and transverse (the right uncinate fasciculus) fibers of the frontal regions, and the cingulum-angular fibers. Our correlation results showed that age-related WM differentially influenced cognitive function, with increased fractional anisotropy values in both the anterior corpus callosum and the right cingulum/angular fibers positively correlated with performance on the visuospatial task in older adults. Moreover, mediation analysis further revealed that the WM tract integrity of the frontal interhemspheric fibers was a significant mediator of age-visuospatial performance relation in older adults, but not in younger adults. These findings support the vulnerability of the frontal WM fibers to normal aging and push forward our understanding of cognitive aging by providing a more integrative view of the neural basis of linkages among aging, cognition, and brain.
Early recovery of interhemispheric functional connectivity after corpus callosotomy
(2019-06-01)
Hung, Sheng-Che
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Lee, Cheng-Chia
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Chen, Hsin-Hung
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Chen, Chien
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Wu, Hsiu-Mei
Objective To investigate whether interhemispheric functional connectivity (FC) recovers in the first year after total callosotomy. Methods Eight epilepsy patients undergoing total callosotomy were recruited. Resting-state functional magnetic resonance imaging was acquired before and after surgery. The precallosotomy and postcallosotomy interhemispheric and intrahemispheric FC was analyzed by using graph theory and voxel-mirrored homotopic connectivity (VMHC). The seizure outcome was scored using the Engel surgical outcome scale. Results After callosotomy (mean postoperative interval = 4 months), the network density, average node degree, characteristic path length, and global efficiency of the whole interhemispheric networks were significantly decreased, compared to those in the precallosotomy networks. However, postcallosotomy interhemispheric FC and homotopic VMHC were not significantly reduced in bilateral frontal and temporal lobes. The network density and average node degree of the intrahemispheric networks were significantly increased. The characteristic path length and global efficiency of intrahemispheric networks were unchanged. Significance The interhemispheric FC may be preserved or recover early within the first postoperative year after total callosotomy, particularly in the frontal and anterior temporal lobes.
Polarization-Sensitive Optical Coherence Tomography for Brain Tumor Characterization
(2019-01-01)
Li, Yun-Qian
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Chiu, Kai-Shih
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Liu, Xin-Rui
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Hsiao, Tien-Yu
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Zhao, Gang
Complete removal of brain tumor is of the most interest to a surgeon because the resection area directly relates to recurrence rate. Although there are many biomedical imaging modalities applied to locate the positions of tumors, they lack the spatial resolution to precisely delineate the boundary between brain tumor and normal brain tissues and are also inconvenient to be used intraoperatively. This study aims to examine the feasibility of the label-free, polarization-sensitive optical coherence tomography (PS-OCT) for distinguishing brain tumors from normal brain tissues. Ex vivo samples were obtained from two patients with grade II and II-III glioma; healthy porcine brain tissues were utilized as the control group. In the results obtained from normal porcine brain, white matter contains significantly higher birefringent property over grey matter indicated by phase retardation. Based on the knowledge obtained from porcine brain experiment, a similar high-hirefringent tissue is observed partially on the edge of the sliced glioma, and such tissue is considered as white matter because glioma originates through the mutation of the healthy white matter's glia cells. Additionally, differences between grey matter and brain tumor are not apparent based on phase retardation images and further histogram analysis. The capability of PS-OCT for distinguishing glioma from white matter is demonstrated. It could he a potential system to facilitate safe and maximum resection area, and finally, lead to ameliorated outcomes.