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- Burzynska, A Z, et al.
(författare)
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Age-related differences in white matter microstructure : region-specific patterns of diffusivity.
- 2010
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Ingår i: NeuroImage. - San Diego ; Orlando, Fla : Elsevier BV. - 1053-8119 .- 1095-9572. ; 49:3, s. 2104-2112
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Tidskriftsartikel (refereegranskat)abstract
- We collected MRI diffusion tensor imaging data from 80 younger (20-32 years) and 63 older (60-71 years) healthy adults. Tract-based spatial statistics (TBSS) analysis revealed that white matter integrity, as indicated by decreased fractional anisotropy (FA), was disrupted in numerous structures in older compared to younger adults. These regions displayed five distinct region-specific patterns of age-related differences in other diffusivity properties: (1) increases in both radial and mean diffusivity; (2) increases in radial diffusivity; (3) no differences in parameters other than FA; (4) a decrease in axial and an increase in radial diffusivity; and (5) a decrease in axial and mean diffusivity. These patterns suggest different biological underpinnings of age-related decline in FA, such as demyelination, Wallerian degeneration, gliosis, and severe fiber loss, and may represent stages in a cascade of age-related degeneration in white matter microstructure. This first simultaneous description of age-related differences in FA, mean, axial, and radial diffusivity requires histological and functional validation as well as analyses of intermediate age groups and longitudinal samples.
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- Burzynska, A Z, et al.
(författare)
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Microstructure of frontoparietal connections predicts cortical responsivity and working memory performance
- 2011
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 21:10, s. 2261-2271
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Tidskriftsartikel (refereegranskat)abstract
- We investigated how the microstructure of relevant white matter connections is associated with cortical responsivity and working memory (WM) performance by collecting diffusion tensor imaging and verbal WM functional magnetic resonance imaging data from 29 young adults. We measured cortical responsivity within the frontoparietal WM network as the difference in blood oxygenation level-dependent (BOLD) signal between 3-back and 1-back conditions. Fractional anisotropy served as an index of the integrity of the superior longitudinal fasciculi (SLF), which connect frontal and posterior regions. We found that SLF integrity is associated with better 3-back performance and greater task-related BOLD responsivity. In addition, BOLD responsivity in right premotor cortex reliably mediated the effects of SLF integrity on 3-back performance but did not uniquely predict 3-back performance after controlling for individual differences in SLF integrity. Our results suggest that task-related adjustments of local gray matter processing are conditioned by the properties of anatomical connections between relevant cortical regions. We suggest that the microarchitecture of white matter tracts influences the speed of signal transduction along axons. This in turn may affect signal summation at neural dendrites, action potential firing, and the resulting BOLD signal change and responsivity.
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- Nevalainen, Nina, et al.
(författare)
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COBRA : A prospective multimodal imaging study of dopamine, brain structure and function, and cognition.
- 2015
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Ingår i: Brain Research. - : Elsevier BV. - 0006-8993 .- 1872-6240. ; 1612, s. 83-103
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Tidskriftsartikel (refereegranskat)abstract
- Cognitive decline is a characteristic feature of normal human aging. Previous work has demonstrated marked interindividual variability in onset and rate of decline. Such variability has been linked to factors such as maintenance of functional and structural brain integrity, genetics, and lifestyle. Still, few, if any, studies have combined a longitudinal design with repeated multimodal imaging and a comprehensive assessment of cognition as well as genetic and lifestyle factors. The present paper introduces the Cognition, Brain, and Aging (COBRA) study, in which cognitive performance and brain structure and function are measured in a cohort of 181 older adults aged 64 to 68 years at baseline. Participants will be followed longitudinally over a 10-year period, resulting in a total of three equally spaced measurement occasions. The measurement protocol at each occasion comprises a comprehensive set of behavioral and imaging measures. Cognitive performance is evaluated via computerized testing of working memory, episodic memory, perceptual speed, motor speed, implicit sequence learning, and vocabulary. Brain imaging is performed using positron emission tomography with [(11)C]-raclopride to assess dopamine D2/D3 receptor availability. Structural magnetic resonance imaging (MRI) is used for assessment of white and gray-matter integrity and cerebrovascular perfusion, and functional MRI maps brain activation during rest and active task conditions. Lifestyle descriptives are collected, and blood samples are obtained and stored for future evaluation. Here, we present selected results from the baseline assessment along with a discussion of sample characteristics and methodological considerations that determined the design of the study.
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