A K Zaleta

Massachusetts General Hospital, Boston, Massachusetts, United States

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Publications (3)18.01 Total impact

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    ABSTRACT: Prior work has demonstrated that the memory dysfunction of Alzheimer's disease (AD) is accompanied by marked cortical pathology in medial temporal lobe (MTL) gray matter. In contrast, changes in white matter (WM) of pathways associated with the MTL have rarely been studied. We used diffusion tensor imaging (DTI) to examine regional patterns of WM tissue changes in individuals with AD. Alterations of diffusion properties with AD were found in several regions including parahippocampal WM, and in regions with direct and secondary connections to the MTL. A portion of the changes measured, including effects in the parahippocampal WM, were independent of gray matter degeneration as measured by hippocampal volume. Examination of regional changes in unique diffusion parameters including anisotropy and axial and radial diffusivity demonstrated distinct zones of alterations, potentially stemming from differences in underlying pathology, with a potential myelin specific pathology in the parahippocampal WM. These results demonstrate that deterioration of neocortical connections to the hippocampal formation results in part from the degeneration of critical MTL and associated fiber pathways.
    Neurobiology of aging 06/2008; 31(2):244-56. DOI:10.1016/j.neurobiolaging.2008.03.013 · 4.85 Impact Factor
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    ABSTRACT: The authors studied presymptomatic individuals with the Huntington disease (HD) mutation to determine whether cortical thinning was present. They found thinning that was regionally selective, semi-independent of striatal volume loss, and correlated with cognitive performance. Early, extensive cortical involvement occurs during the preclinical stages of HD.
    Neurology 10/2005; 65(5):745-7. DOI:10.1212/01.wnl.0000174432.87383.87 · 8.30 Impact Factor
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    ABSTRACT: Cerebral white matter (WM) undergoes various degenerative changes with normal aging, including decreases in myelin density and alterations in myelin structure. We acquired whole-head, high-resolution diffusion tensor images (DTI) in 38 participants across the adult age span. Maps of fractional anisotropy (FA), a measure of WM microstructure, were calculated for each participant to determine whether particular fiber systems of the brain are preferentially vulnerable to WM degeneration. Regional FA measures were estimated from nine regions of interest in each hemisphere and from the genu and splenium of the corpus callosum (CC). The results showed significant age-related decline in FA in frontal WM, the posterior limb of the internal capsule (PLIC), and the genu of the CC. In contrast, temporal and posterior WM was relatively preserved. These findings suggest that WM alterations are variable throughout the brain and that particular fiber populations within prefrontal region and PLIC are most vulnerable to age-related degeneration.
    Neurobiology of Aging 08/2005; 26(8):1215-27. DOI:10.1016/j.neurobiolaging.2004.09.017 · 4.85 Impact Factor