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1: Cereb Cortex. 2005 Jun;15(6):732-9. Epub 2004 Sep 15.
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Frontal-hippocampal double dissociation between normal aging and Alzheimer's disease.

Head D, Snyder AZ, Girton LE, Morris JC, Buckner RL.

Howard Hughes Medical Institute, One Brookings Drive, Department of Psychology, Washington University, St Louis, MO 63130, USA. dhead@artsci.wustl.edu

Controversy persists regarding whether Alzheimer's disease (AD) is a distinct entity or instead exists on a continuum with nondemented aging. To explore this issue, volumetric analyses of callosal and hippocampal regions were performed on 150 participants aged 18-93 years. Group-level analyses revealed that nondemented age-related differences were greater in anterior than posterior callosal regions and were not augmented by early-stage AD. In contrast, early-stage AD was associated with substantial reduction in hippocampal volume. Examination of the 100 older adults using regression analyses demonstrated age-associated differences in callosal volume that were similar in demented and nondemented individuals. Early-stage AD was again characterized by a marked reduction in hippocampal volume while age alone induced only mild differences in hippocampal volume. As a final analysis, the formal double dissociation was confirmed by comparing the effects of age directly against the effects of dementia. These results suggest a multiple-component model of aging. One process, associated with AD, manifests early and prominently in the medial temporal lobe. A separate process, ubiquitous in aging, affects brain white matter with an anterior-to-posterior gradient and may underlie the executive difficulties common in aging.

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PMID: 15371293 [PubMed - indexed for MEDLINE]