J Clin Neurol.  2017 Oct;13(4):387-393. 10.3988/jcn.2017.13.4.387.

Functional Connectivity of the Hippocampus in Early- and vs. Late-Onset Alzheimer's Disease

Affiliations
  • 1Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea. khpark@gachon.ac.kr
  • 2Neuroscience Research Institute, Gachon University, Incheon, Korea. ydson@gachon.ac.kr
  • 3Department of Family Medicine, Gachon University Gil Medical Center, Incheon, Korea.
  • 4Department of Radiology, Gachon University Gil Medical Center, Incheon, Korea.
  • 5Department of Biomedical Engineering, College of Health Science, Gachon University, Incheon, Korea.

Abstract

BACKGROUND
AND PURPOSE: Early-onset Alzheimer's disease (EOAD) and late-onset Alzheimer's disease (LOAD) have different clinical and neuroimaging characteristics, but memory decline is usually present in both types. However, there have been few functional studies focused on the hippocampus in Alzheimer's disease. We therefore investigated the functional connectivity between the hippocampus and other brain regions using resting-state fMRI and compared the findings between EOAD and LOAD.
METHODS
We recruited 13 patients with EOAD and 19 patients with LOAD at the early disease stage. Twenty-one young controls and ten old controls were also recruited. Each participant completed a standardized neuropsychological battery of tests and underwent T1-weighted structural MRI. fMRI data were acquired during the resting state using 3-T MRI. The functional connectivity to the hippocampus was calculated based on automated anatomical labeling templates.
RESULTS
The functional connectivity from the hippocampus to other brain regions differed between patients with EOAD and LOAD. The LOAD patients showed decreased hippocampal connectivity to cortical regions, such as to the middle temporal cortex, orbitofrontal cortex, postcentral cortex, supramarginal cortex, and rolandic operculum. In contrast, EOAD patients showed smaller functional changes of the cortical regions connected to the hippocampus, such as the middle frontal cortex.
CONCLUSIONS
EOAD and LOAD patients exhibited different hippocampal connectivity. The memory decline in EOAD may be due to brain areas other than the hippocampus.

Keyword

early-onset Alzheimer's disease; late-onset Alzheimer's disease; functional connectivity; hippocampus
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