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author:("Heo, susi")
1.  BDNF is Associated With Age-Related Decline in Hippocampal Volume 
Hippocampal volume shrinks in late adulthood, but the neuromolecular factors that trigger hippocampal decay in aging humans remains a matter of speculation. In rodents, brain derived neurotrophic factor (BDNF) promotes the growth and proliferation of cells in the hippocampus and is important in long-term potentiation and memory formation. In humans, circulating levels of BDNF decline with advancing age and a genetic polymorphism for BDNF has been related to gray matter volume loss in old age. In this study, we tested whether age-related reductions in serum levels of BDNF would be related to shrinkage of the hippocampus and memory deficits in older adults. Hippocampal volume was acquired by automated segmentation of magnetic resonance images in 142 older adults without dementia. The caudate nucleus was also segmented and examined in relation to levels of serum BDNF. Spatial memory was tested using a paradigm in which memory load was parametrically increased. We found that increasing age was associated with smaller hippocampal volumes, reduced levels of serum BDNF, and poorer memory performance. Lower levels of BDNF were associated with smaller hippocampi and poorer memory, even when controlling for the variation related to age. In an exploratory mediation analysis, hippocampal volume mediated the age-related decline in spatial memory and BDNF mediated the age-related decline in hippocampal volume. Caudate nucleus volume was unrelated to BDNF levels or spatial memory performance. Our results identify serum BDNF as a significant factor related to hippocampal shrinkage and memory decline in late adulthood.
PMCID: PMC3069644  PMID: 20392958
brain-derived neurotrophic factor; hippocampus; human; brain; caudate nucleus; aging
2.  Resting Hippocampal Blood Flow, Spatial Memory and Aging 
Brain research  2009;1315C:119.
Aging is accompanied by a general deterioration of fluid cognitive processes and a reduction in resting cerebral blood flow (CBF). While the two phenomena have been observed independently, it is uncertain whether individual differences in cerebral blood flow are reliably associated with cognitive functioning in older adults. Furthermore, previous studies have concentrated primarily on gross measures of cognition and global gray matter CBF, leaving open the possibility that perfusion of specific brain regions may relate differentially to distinct cognitive domains. The present study sought to provide a more focused treatment of CBF and cognitive function in the context of aging by investigating the relationships among aging, spatial memory and resting hippocampal blood flow, both between and within younger and older adult groups. Blood flow was quantified using a novel Flow-Enhanced Signal Intensity (FENSI) technique which provides a localized, functionally-relevant measure of volumetric flow across a given unit area. As expected, we found that aging was associated with poorer spatial memory and reduced resting CBF. Moreover, hippocampal blood flow was positively correlated with spatial memory performance in the older adult group, suggesting that increased blood flow to the hippocampus is associated with superior memory performance in older adults. These results demonstrate a region-specific CBF—cognition relationship and thereby offer new insight into the complex connection between the aging brain and behavior.
PMCID: PMC2822086  PMID: 20026320
hippocampus; cerebral blood flow; brain perfusion; cognition; memory; aging
3.  Plasticity of Brain Networks in a Randomized Intervention Trial of Exercise Training in Older Adults 
Research has shown the human brain is organized into separable functional networks during rest and varied states of cognition, and that aging is associated with specific network dysfunctions. The present study used functional magnetic resonance imaging (fMRI) to examine low-frequency (0.008 < f < 0.08 Hz) coherence of cognitively relevant and sensory brain networks in older adults who participated in a 1-year intervention trial, comparing the effects of aerobic and non-aerobic fitness training on brain function and cognition. Results showed that aerobic training improved the aging brain's resting functional efficiency in higher-level cognitive networks. One year of walking increased functional connectivity between aspects of the frontal, posterior, and temporal cortices within the Default Mode Network and a Frontal Executive Network, two brain networks central to brain dysfunction in aging. Length of training was also an important factor. Effects in favor of the walking group were observed only after 12 months of training, compared to non-significant trends after 6 months. A non-aerobic stretching and toning group also showed increased functional connectivity in the DMN after 6 months and in a Frontal Parietal Network after 12 months, possibly reflecting experience-dependent plasticity. Finally, we found that changes in functional connectivity were behaviorally relevant. Increased functional connectivity was associated with greater improvement in executive function. Therefore the study provides the first evidence for exercise-induced functional plasticity in large-scale brain systems in the aging brain, using functional connectivity techniques, and offers new insight into the role of aerobic fitness in attenuating age-related brain dysfunction.
PMCID: PMC2947936  PMID: 20890449
exercise; aging; functional connectivity; fMRI; default mode network; executive function; aerobic fitness

Results 1-3 (3)