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Center for the Study of Aging and Human Development, Duke University Medical Center, USA.
Neurobiology of aging (Impact Factor: 5.01). 08/2008; 29(7):1070-9. DOI: 10.1016/j.neurobiolaging.2007.02.008
Source: PubMed


Previous research suggests that, in reaction time (RT) measures of episodic memory retrieval, the unique effects of adult age are relatively small compared to the effects aging shares with more elementary abilities such as perceptual speed. Little is known, however, regarding the mechanisms of perceptual speed. We used diffusion tensor imaging (DTI) to test the hypothesis that white matter integrity, as indexed by fractional anisotropy (FA), serves as one mechanism of perceptual slowing in episodic memory retrieval. Results indicated that declines in FA in the pericallosal frontal region and in the genu of the corpus callosum, but not in other regions, mediated the relationship between perceptual speed and episodic retrieval RT. This relation held, though to a different degree, for both hits and correct rejections. These findings suggest that white matter integrity in prefrontal regions is one mechanism underlying the relation between individual differences in perceptual speed and episodic retrieval.

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Available from: Scott Huettel, Aug 25, 2014
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    • "structures that are important to the efficiency of interhemispheric communication, and are linked to perceptual speed (Bucur et al. 2008) and cognitive decline in aging (Lövdén et al. 2010). Finally, cluster 5 included portions of the thalamus, a major relay of information not only between the periphery and the cortex, but also between cortical areas (Sherman 2007). "
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    ABSTRACT: The objective of this work was to test the hypotheses that a) more frequent cognitive activity in late life is associated with higher brain diffusion anisotropy and lower trace of the diffusion tensor, and b) brain diffusion characteristics partially mediate the association of late life cognitive activity with cognition. As part of a longitudinal cohort study, 379 older people without dementia rated their frequency of participation in cognitive activities, completed a battery of cognitive function tests, and underwent diffusion tensor imaging. We used tract-based spatial statistics to test the association between late life cognitive activity and brain diffusion characteristics. Clusters with statistically significant findings defined regions of interest in which we tested the hypothesis that diffusion characteristics partially mediate the association of late life cognitive activity with cognition. More frequent cognitive activity in late life was associated with higher level of global cognition after adjustment for age, sex, education, and indicators of early life cognitive enrichment (p = 0.001). More frequent cognitive activity was also related to higher fractional anisotropy in the left superior and inferior longitudinal fasciculi, left fornix, and corpus callosum, and lower trace in the thalamus (p < 0.05, FWE-corrected). After controlling for fractional anisotropy or trace from these regions, the regression coefficient for the association of late life cognitive activity with cognition was reduced by as much as 26 %. These findings suggest that the association of late life cognitive activity with cognition may be partially mediated by brain diffusion characteristics.
    Brain Imaging and Behavior 05/2015; DOI:10.1007/s11682-015-9405-5 · 4.60 Impact Factor
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    • "Pagani et al., 2005] and developmental studies to characterize changes associated with aging [e.g. Bucur et al., 2008; Dubois et al., 2008]. As for DWI studies involving HD participants, many have focused on WM of the motor loop [Bohanna et al., 2011; Della Nave et al., 2010; Rosas et al., 2006; Stoffers et al., 2010], periventricular region [Mascalchi et al., 2004], corpus callosum [Bohanna et al., 2011; Della Nave et al., 2010; Di Paola et al., 2012; Dumas et al., 2012; Mü ller et al., 2011; Rosas et al., 2006, 2010; Sritharan et al., 2010; Weaver et al., 2009], corona radiata [Bohanna et al., 2011; Della Nave et al., 2010; Stoffers et al., 2010; Weaver et al., 2009], and whole brain [Mascalchi et al., 2004; Rosas et al., 2006]. "
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    ABSTRACT: Huntington's disease (HD) is a devastating neurodegenerative disease with no effective disease-modifying treatments. There is considerable interest in finding reliable indicators of disease progression to judge the efficacy of novel treatments that slow or stop disease onset before debilitating signs appear. Diffusion-weighted imaging (DWI) may provide a reliable marker of disease progression by characterizing diffusivity changes in white matter (WM) in individuals with prodromal HD. The prefrontal cortex (PFC) may play a role in HD progression due to its prominent striatal connections and documented role in executive function. This study uses DWI to characterize diffusivity in specific regions of PFC WM defined by FreeSurfer in 53 prodromal HD participants and 34 controls. Prodromal HD individuals were separated into three CAG-Age Product (CAP) groups (16 low, 22 medium, 15 high) that indexed baseline progression. Statistically significant increases in mean diffusivity (MD) and radial diffusivity (RD) among CAP groups relative to controls were seen in inferior and lateral PFC regions. For MD and RD, differences among controls and HD participants tracked with baseline disease progression. The smallest difference was for the low group and the largest for the high group. Significant correlations between Trail Making Test B (TMTB) and mean fractional anisotropy (FA) and/or RD paralleled group differences in mean MD and/or RD in several right hemisphere regions. The gradient of effects that tracked with CAP group suggests DWI may provide markers of disease progression in future longitudinal studies as increasing diffusivity abnormalities in the lateral PFC of prodromal HD individuals. Hum Brain Mapp, 2013. © 2013 Wiley Periodicals, Inc.
    Human Brain Mapping 04/2014; 35(4). DOI:10.1002/hbm.22273 · 5.97 Impact Factor
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    • "Prior work suggests that DTI may provide information about different pathophysiological processes and may be one of the most sensitive neuroimaging biomarkers of vascular damage [35], [36], [37], [8]. Although, FA is the most widely studied diffusion metric, there is a growing interest in investigating WM microstructural mechanism underlying the FA change by analyzing other – more direct – diffusion metrics, such as axial (AD) and radial (RD) diffusivity. "
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    ABSTRACT: After stroke, white matter integrity can be affected both locally and distally to the primary lesion location. It has been shown that tract disruption in mirror's regions of the contralateral hemisphere is associated with degree of functional impairment. Fourteen patients suffering right hemispheric focal stroke (S) and eighteen healthy controls (HC) underwent Diffusion Weighted Imaging (DWI) and neuropsychological assessment. The stroke patient group was divided into poor (SP; n = 8) and good (SG; n = 6) cognitive recovery groups according to their cognitive improvement from the acute phase (72 hours after stroke) to the subacute phase (3 months post-stroke). Whole-brain DWI data analysis was performed by computing Diffusion Tensor Imaging (DTI) followed by Tract Based Spatial Statistics (TBSS). Assessment of effects was obtained computing the correlation of the projections on TBSS skeleton of Fractional Anisotropy (FA) and Radial Diffusivity (RD) with cognitive test results. Significant decrease of FA was found only in right brain anatomical areas for the S group when compared to the HC group. Analyzed separately, stroke patients with poor cognitive recovery showed additional significant FA decrease in several left hemisphere regions; whereas SG patients showed significant decrease only in the left genu of corpus callosum when compared to the HC. For the SG group, whole brain analysis revealed significant correlation between the performance in the Semantic Fluency test and the FA in the right hemisphere as well as between the performance in the Grooved Pegboard Test (GPT) and theTrail Making Test-part A and the FA in the left hemisphere. For the SP group, correlation analysis revealed significant correlation between the performance in the GPT and the FA in the right hemisphere.
    PLoS ONE 01/2014; 9(1):e86119. DOI:10.1371/journal.pone.0086119 · 3.23 Impact Factor
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