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Comparative Study
. 2011 Oct;21(10):2399-407.
doi: 10.1093/cercor/bhr025. Epub 2011 Mar 7.

Relationships between β-amyloid and functional connectivity in different components of the default mode network in aging

Elizabeth C Mormino  1 , Andre Smiljic, Amynta O Hayenga, Susan H Onami, Michael D Greicius, Gil D Rabinovici, Mustafa Janabi, Suzanne L Baker, Irene V Yen, Cindee M Madison, Bruce L Miller, William J Jagust
Affiliations
Comparative Study

Relationships between β-amyloid and functional connectivity in different components of the default mode network in aging

Elizabeth C Mormino et al. Cereb Cortex. 2011 Oct.

Abstract

Although beta-amyloid (Aβ) deposition is a characteristic feature of Alzheimer's disease (AD), this pathology is commonly found in elderly normal controls (NC). The pattern of Aβ deposition as detected with Pittsburgh compound-B positron emission tomography (PIB-PET) imaging shows substantial spatial overlap with the default mode network (DMN), a group of brain regions that typically deactivates during externally driven cognitive tasks. In this study, we show that DMN functional connectivity (FC) during rest is altered with increasing levels of PIB uptake in NC. Specifically, FC decreases were identified in regions implicated in episodic memory (EM) processing (posteromedial cortex, ventral medial prefrontal cortex, and angular gyrus), whereas connectivity increases were detected in dorsal and anterior medial prefrontal and lateral temporal cortices. This pattern of decreases is consistent with previous studies that suggest heightened vulnerability of EM-related brain regions in AD, whereas the observed increases in FC may reflect a compensatory response.

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Figures

Figure 1.
Figure 1.
DMN FC and global PIB uptake overlap. One sample t-test of DMN best-fit components (yellow), 2-sample t-test between high and low PIB subjects (blue), and overlap (red) are displayed. These maps highlight congruence and incongruence between the DMN and the brain regions showing high levels of Aβ deposition. The greatest amount of overlap is in precuneus/posterior cingulate, medial prefrontal, and angular gyri. Although PIB uptake is more diffuse than DMN, there is minimal overlap in retrosplenial and medial temporal portions of the DMN.
Figure 2.
Figure 2.
t-Maps from voxelwise analysis correlating global PIB with DMN FC. Cool colors reflect a negative relationship, whereas warm colors reflect a positive relationship between global PIB and DMN FC.
Figure 3.
Figure 3.
Boxplots of global and regional PIB values in high PIB NC (white boxes) and AD (gray boxes). Although AD subjects show heightened PIB, overlap between AD and NC suggests the early Aβ deposition in NC. Despite low PIB uptake in L RSC, L amPFC, and L MTG, these regions show FC changes with increased levels of global PIB.
See this image and copyright information in PMC

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