Abstract
Both normal aging and Alzheimer's disease (AD) have been associated with a reduction in functional brain connectivity. It is unknown how connectivity patterns due to aging and AD compare. Here, we investigate functional brain connectivity in 12 young adults (mean age 22.8 ± 2.8), 12 older adults (mean age 73.1 ± 5.2) and 12 AD patients (mean age 74.0 ± 5.2; mean MMSE 22.3 ± 2.5). Participants were scanned during 6 different sessions with resting state functional magnetic resonance imaging (RS-fMRI), resulting in 72 scans per group. Voxelwise connectivity with 10 functional networks was compared between groups (p < 0.05, corrected). Normal aging was characterized by widespread decreases in connectivity with multiple brain networks, whereas AD only affected connectivity between the default mode network (DMN) and precuneus. The preponderance of effects was associated with regional gray matter volume. Our findings indicate that aging has a major effect on functional brain interactions throughout the entire brain, whereas AD is distinguished by additional diminished posterior DMN-precuneus coherence.
Highlights
When age progresses, the brain is subjected to many changes that are related to deterioration of sensory, motor and intellectual functioning (Salthouse, 1996; Li and Lindenberger, 2002; Fandakova et al, 2014)
Significant F-test results pointed to differences in connectivity in Alzheimer’s disease (AD) patients vs. elderly controls and in older vs. young adults for all networks, except the cerebellar network
AD patients and elderly controls differed in connectivity with the default mode network (DMN), that showed lower connectivity with the precuneus in AD patients compared to older adults
Summary
The brain is subjected to many changes that are related to deterioration of sensory, motor and intellectual functioning (Salthouse, 1996; Li and Lindenberger, 2002; Fandakova et al, 2014). In Alzheimer’s disease (AD), a gradual worsening in memory and other cognitive domains occurs, accompanied by a notable reduction in independency and daily life functioning (McKhann et al, 2011). This age and dementia related decline in function is likely to be associated with a loss of integrity of large-scale brain networks (Mesulam, 1998). Both aging and AD are most prominently characterized by a reduction in DMN connectivity (Greicius et al, 2004; Damoiseaux et al, 2008; Biswal et al, 2010; Koch et al, 2010; Zhang et al, 2010; Pievani et al, 2011; Hafkemeijer et al, 2012; Ferreira and Busatto, 2013; Dennis and Thompson, 2014)
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