Increased posterior default mode network activity and structural connectivity in young adult APOE-ε4 carriers: a multimodal imaging investigation
Carl J. Hodgetts, Jonathan P. Shine, Huw Williams, Mark Postans, Rebecca Sims, Julie Williams, Andrew D. Lawrence, Kim S. Graham
Neurobiology of Aging September 22, 2018 DOI: 10.1016/j.neurobiolaging.2018.08.026 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Cross-sectional neuroimaging study Longitudinal Peer reviewed |
|---|---|
| Sample size | 30 |
| Population | Young adults (mean age 20 years), half APOE-ε4 carriers |
| Topics | Default mode network |
| Citations | 39 |
| Key findings | APOE-ε4 carriers showed lower mean diffusivity and higher fractional anisotropy in the parahippocampal cingulum bundle than noncarriers, but not in a control tract. This tract's microstructure was selectively associated with posterior default mode network and medial temporal lobe activity during a scene discrimination task. The authors argue these findings support a lifespan view in which early-life connectivity changes in vulnerable hubs may reflect reduced network efficiency and portend faster decline. |
Abstract
Young adult APOE-ε4 carriers show increased activity in posterior regions of the default mode network (pDMN), but how this is related to structural connectivity is unknown. Thirty young adults (one half of whom were APOE-ε4 carriers; mean age 20 years) were scanned using both diffusion and functional magnetic resonance imaging. The parahippocampal cingulum bundle (PHCB)-which links the pDMN and the medial temporal lobe-was manually delineated in individual participants using deterministic tractography. Measures of tract microstructure (mean diffusivity and fractional anisotropy) were then extracted from these tract delineations. APOE-ε4 carriers had lower mean diffusivity and higher fractional anisotropy relative to noncarriers in PHCB, but not in a control tract (the inferior longitudinal fasciculus). Furthermore, PHCB microstructure was selectively associated with pDMN (and medial temporal lobe) activity during a scene discrimination task known to be sensitive to Alzheimer's disease. These findings are consistent with a lifespan view of Alzheimer's disease risk, where early-life, connectivity-related changes in specific, vulnerable "hubs" (e.g., pDMN) lead to increased neural activity. Critically, such changes may reflect reduced network efficiency/flexibility in APOE-ε4 carriers, which in itself may portend a faster decline in connectivity over the lifespan and ultimately trigger early amyloid-β deposition in later life.
Comparable studies
Other experimental studies on default mode network, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Functional connectivity of default mode network components: Correlation, anticorrelation, and causality Healthy subjects | 2008 | Observational study using resting-state fMRI and seed correlation analysis | |
| Patterns of Brain Activity Supporting Autobiographical Memory, Prospection, and Theory of Mind, and Their Relationship to the Default Mode Network Healthy subjects | 2009 | Experimental study using fMRI | |
| Dynamic reconfiguration of the default mode network during narrative comprehension Human subjects | 2016 | Experimental study | |
| Broadband Cortical Desynchronization Underlies the Human Psychedelic State Healthy human participants | 2013 | Experimental study | |
| The brain on art: intense aesthetic experience activates the default mode network Human observers | 2012 | Observational study with fMRI and behavioral analysis |