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      Amyloid-β Associated Cortical Thinning in Clinically Normal Elderly

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          Abstract

          Objective

          Both amyloid-β (Aβ) deposition and brain atrophy are associated with Alzheimer's disease (AD) and the disease process likely begins many years before symptoms appear. We sought to determine whether clinically normal (CN) older individuals with Aβ deposition revealed by positron emission tomography (PET) imaging using Pittsburgh Compound B (PiB) also have evidence of both cortical thickness and hippocampal volume reductions in a pattern similar to that seen in AD.

          Methods

          A total of 119 older individuals (87 CN subjects and 32 patients with mild AD) underwent PiB PET and high-resolution structural magnetic resonance imaging (MRI). Regression models were used to relate PiB retention to cortical thickness and hippocampal volume.

          Results

          We found that PiB retention in CN subjects was (1) age-related and (2) associated with cortical thickness reductions, particularly in parietal and posterior cingulate regions extending into the precuneus, in a pattern similar to that observed in mild AD. Hippocampal volume reduction was variably related to Aβ deposition.

          Interpretation

          We conclude that Aβ deposition is associated with a pattern of cortical thickness reduction consistent with AD prior to the development of cognitive impairment. ANN NEUROL 2010;

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          Most cited references33

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          Development and validation of a geriatric depression screening scale: a preliminary report.

          A new Geriatric Depression Scale (GDS) designed specifically for rating depression in the elderly was tested for reliability and validity and compared with the Hamilton Rating Scale for Depression (HRS-D) and the Zung Self-Rating Depression Scale (SDS). In constructing the GDS a 100-item questionnaire was administered to normal and severely depressed subjects. The 30 questions most highly correlated with the total scores were then selected and readministered to new groups of elderly subjects. These subjects were classified as normal, mildly depressed or severely depressed on the basis of Research Diagnostic Criteria (RDC) for depression. The GDS, HRS-D and SDS were all found to be internally consistent measures, and each of the scales was correlated with the subject's number of RDC symptoms. However, the GDS and the HRS-D were significantly better correlated with RDC symptoms than was the SDS. The authors suggest that the GDS represents a reliable and valid self-rating depression screening scale for elderly populations.
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            Parietal lobe contributions to episodic memory retrieval.

            Although the parietal lobe is not traditionally thought to support declarative memory, recent event-related fMRI studies of episodic retrieval have consistently revealed a range of memory-related influences on activation in lateral posterior parietal cortex (PPC) and precuneus extending into posterior cingulate and retrosplenial cortex. This article surveys the fMRI literature on PPC activation during remembering, a literature that complements earlier electroencephalography data. We consider these recent memory-related fMRI responses within the context of classical ideas about parietal function that emphasize space-based attention and motor intention. We conclude by proposing three hypotheses concerning how parietal cortex might contribute to memory.
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              Frequent amyloid deposition without significant cognitive impairment among the elderly.

              To characterize the prevalence of amyloid deposition in a clinically unimpaired elderly population, as assessed by Pittsburgh Compound B (PiB) positron emission tomography (PET) imaging, and its relationship to cognitive function, measured with a battery of neuropsychological tests. Subjects underwent cognitive testing and PiB PET imaging (15 mCi for 90 minutes with an ECAT HR+ scanner). Logan graphical analysis was applied to estimate regional PiB retention distribution volume, normalized to a cerebellar reference region volume, to yield distribution volume ratios (DVRs). University medical center. From a community-based sample of volunteers, 43 participants aged 65 to 88 years who did not meet diagnostic criteria for Alzheimer disease or mild cognitive impairment were included. Regional PiB retention and cognitive test performance. Of 43 clinically unimpaired elderly persons imaged, 9 (21%) showed evidence of early amyloid deposition in at least 1 brain area using an objectively determined DVR cutoff. Demographic characteristics did not differ significantly between amyloid-positive and amyloid-negative participants, and neurocognitive performance was not significantly worse among amyloid-positive compared with amyloid-negative participants. Amyloid deposition can be identified among cognitively normal elderly persons during life, and the prevalence of asymptomatic amyloid deposition may be similar to that of symptomatic amyloid deposition. In this group of participants without clinically significant impairment, amyloid deposition was not associated with worse cognitive function, suggesting that an elderly person with a significant amyloid burden can remain cognitively normal. However, this finding is based on relatively small numbers and needs to be replicated in larger cohorts. Longitudinal follow-up of these subjects will be required to support the potential of PiB imaging to identify preclinical Alzheimer disease, or, alternatively, to show that amyloid deposition is not sufficient to cause Alzheimer disease within some specified period.
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                Author and article information

                Journal
                Ann Neurol
                Ann. Neurol
                ana
                Annals of Neurology
                Wiley Subscription Services, Inc., A Wiley Company (Hoboken )
                0364-5134
                1531-8249
                June 2011
                17 March 2011
                : 69
                : 6
                : 1032-1042
                Affiliations
                [1 ]Department of Radiology, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School Boston, MA
                [2 ]Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School Boston, MA
                [3 ]Department of Neurology, Brigham and Women's Hospital, Harvard Medical School Boston, MA
                [4 ]Neurology, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School Boston, MA
                [5 ]Computer Science and Artificial Intelligence Laboratory, Electrical Engineering and Computer Science, Health Science and Technology, Massachusetts Institute of Technology Cambridge, MA
                [6 ]Department of Neurology, Warren Alpert Medical School, Brown University Providence, RI
                [7 ]Memory and Aging Program, Butler Hospital Providence, RI
                [8 ]Tufts School of Medicine Boston, MA
                [9 ]Department of Psychology and Center for Brain Science, Harvard University Cambridge, MA
                [10 ]Psychiatry, Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School Boston, MA
                [11 ]Howard Hughes Medical Institute Cambridge, MA
                Author notes
                Address correspondence to Dr Johnson, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Bartlett 507, 33 Fruit Street, Boston, MA 02114. E-mail: kajohnson@ 123456partners.org

                Additional Supporting Information can be found in the online version of this article.

                Article
                10.1002/ana.22333
                3117980
                21437929
                56816ad8-4f29-49cb-a89d-7a1b7f6c1c34
                Copyright © 2010 American Neurological Association

                Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2.5, which does not permit commercial exploitation.

                History
                : 06 July 2010
                : 06 October 2010
                : 08 November 2010
                Categories
                Original Articles

                Neurology
                Neurology

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