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Relationships between default-mode network connectivity, medial temporal lobe structure, and age-related memory
Andrew M Ward1, Elizabeth C Mormino2, Willem Huijbers1
1Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA.
Neurobiology of Aging
|August 13, 2014
Summary
Aging impacts memory by shrinking the hippocampus and entorhinal cortex and reducing default-mode network connectivity. These brain changes explain most age-related memory decline.
Area of Science:
- Neuroscience
- Cognitive Aging Research
Background:
- Advanced aging negatively affects memory performance.
- Brain aging is linked to medial temporal lobe shrinkage (hippocampus, entorhinal cortex) and altered default-mode network (DMN) connectivity.
- The precise role of these neuroimaging markers in age-related memory deficits is debated.
Purpose of the Study:
- To investigate the relationships between memory performance, hippocampus volume, entorhinal cortex thickness, and DMN connectivity across the adult lifespan.
- To determine if these neuroimaging markers mediate the effects of age on memory.
- To explore the sequential relationship of these markers in older adults.
Main Methods:
- Cross-sectional study involving 182 older adults (mean age 74.6 years) and 66 young adults (mean age 22.2 years).
- Assessment of memory performance, hippocampus volume, entorhinal cortex thickness, and DMN connectivity using neuroimaging techniques.
- Statistical analyses including mediation and structural equation modeling.
Main Results:
- Significant age-related differences were observed in all imaging markers and memory performance.
- Hippocampus volume, entorhinal cortex thickness, and DMN connectivity each significantly mediated the relationship between age and memory.
- These markers collectively accounted for a substantial portion of age-related memory variance.
- In older adults, DMN connectivity and hippocampus volume were independently associated with memory performance.
Conclusions:
- Neuroimaging markers of brain aging, including structural changes in the hippocampus and entorhinal cortex and altered DMN connectivity, are significantly associated with age-related memory decline.
- Entorhinal cortex thinning may precede reductions in DMN connectivity and hippocampus volume, ultimately contributing to memory deficits in aging.
- These findings elucidate key neural mechanisms underlying cognitive aging and memory impairment.
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