Neurobiology of aging
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Neurobiology of aging · Mar 2010
Randomized Controlled TrialIs age a key determinant of mortality and neurological outcome after acute traumatic spinal cord injury?
Given the potential impact of age on mortality, neurological outcomes and the extent of post-traumatic neural degeneration, we examined these issues using a large, prospectively accrued clinical database (n=485) supplemented by analysis of postmortem spinal cord tissue (n=12) to compare axonal survival and white matter degeneration in younger versus elderly individuals with spinal cord injury (SCI). Elderly individuals (> or = 65 years) had significantly greater mortality rates than younger individuals at 30 days, at 6 months and at 1 year following SCI (46.88% versus 4.86%, respectively; p<0.0001). ⋯ Correspondingly, neuroanatomical analysis of postmortem spinal cord tissue revealed no significant age-related differences for extent of myelin degeneration or number of intact axons within sensory, motor and autonomic spinal cord tracts post-SCI. Treatment protocols for SCI need to identify preventable predictors of mortality in the elderly post-SCI, recognizing that the potential for neurological recovery among elderly survivors of SCI is similar to that of younger individuals.
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Neurobiology of aging · Mar 2010
Age-related slowing of task switching is associated with decreased integrity of frontoparietal white matter.
A body of research has demonstrated age-related slowing on tasks that emphasize cognitive control, such as task switching. However, little is known about the neural mechanisms that contribute to this age-related slowing. To address this issue, the present study used both fMRI and DTI in combination with a standard task switching paradigm. ⋯ Results demonstrated a negative correlation between switch cost RT and FA in left frontoparietal WM in both young and older groups. In addition, age-related FA decline in the same frontoparietal WM region was found to mediate age-related increases in RT switch costs. These findings identify decreased integrity of frontoparietal WM as one mechanism contributing to age-related increases in RT switch costs.
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Neurobiology of aging · Mar 2010
Diffusion tensor imaging of deep gray matter brain structures: effects of age and iron concentration.
Diffusion tensor imaging (DTI) of the brain has become a mainstay in the study of normal aging of white matter, and only recently has attention turned to the use of DTI to examine aging effects in gray matter structures. Of the many changes in the brain that occur with advancing age is increased presence of iron, notable in selective deep gray matter structures. In vivo detection and measurement of iron deposition is possible with magnetic resonance imaging (MRI) because of iron's effect on signal intensity. ⋯ Signal intensity measured with DWI was lower in the putamen of elderly than young adults, whereas the opposite was observed for the white matter region and thalamus. As a retrospective study based on legacy data, the FDRI estimates were based on FSE sequences, which underestimated the classical FDRI index of brain iron. Nonetheless, the differential effects of age on DTI metrics in subcortical gray matter structures compared with white matter tracts appears to be related, at least in part, to local iron content, which in the elderly of the present study was prominent in the FDRI estimate of the putamen and visibly striking in the diffusion-weighted image of the basal ganglia structures.
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Neurobiology of aging · Mar 2010
Age-related differences in pain sensitivity and regional brain activity evoked by noxious pressure.
Compared with young adults, older people report more chronic pain complaints, and show reduced tolerance to experimental pain. Atrophy of brain parenchyma in normal ageing is well documented, with grey matter reduction occurring across many regions known to be involved in pain processing. However, the functional consequences of these changes, in particular their contribution toward age-related differences in pain perception and report, are yet to be elucidated. ⋯ Both groups showed significant pain-related activity in a common network of areas including the insula, cingulate, posterior parietal and somatosensory cortices. However, compared with older adults, young subjects showed significantly greater activity in the contralateral putamen and caudate, which could not be accounted for by increased age-associated shrinkage in these regions. The age-related difference in pain-evoked activity seen in the present study may reflect reduced functioning of striatal pain modulatory mechanisms with advancing age.
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Neurobiology of aging · Mar 2010
Quantitative fiber tracking of lateral and interhemispheric white matter systems in normal aging: relations to timed performance.
The integrity of white matter, as measured in vivo with diffusion tensor imaging (DTI), is disrupted in normal aging. A current consensus is that in adults advancing age affects anterior brain regions disproportionately more than posterior regions; however, the mainstay of studies supporting this anterior-posterior gradient is based primarily on measures of the corpus callosum. Using our quantitative fiber tracking approach, we assessed fiber tract integrity of samples of major white matter cortical, subcortical, interhemispheric, and cerebellar systems (11 bilateral and 2 callosal) on DTI data collected at 1.5T magnet strength. ⋯ By contrast, in women the age effect was present in both callosal regions, albeit modestly more so in the genu than splenium. Functional meaningfulness of these age-related differences was supported by significant correlations between DTI signs of white matter degradation and poorer performance on cognitive or motor tests. This survey of multiple fiber systems throughout the brain revealed a differential pattern of age's effect on regional FA and diffusivity and suggests mechanisms of functional degradation, attributed at least in part to compromised fiber microstructure affecting myelin and axonal morphology.