Opposing Effects of Aging on Large-Scale Brain Systems for Memory Encoding and Cognitive Control

Abstract

Episodic memory declines with advancing age. Neuroimaging studies have associated such decline to age-related changes in general cognitive-control networks as well as to changes in process-specific encoding or retrieval networks. To assess the specific influence of aging on encoding and retrieval processes and associated brain systems, it is vital to dissociate encoding and retrieval from each other and from shared cognitive-control processes. We used multivariate partial-least-squares to analyze functional magnetic resonance imaging data from a large population-based sample (n ϭ 292, 25-80 years). The participants performed a face-name paired-associates task and an active baseline task. The analysis revealed two significant network patterns. The first reflected a process-general encoding-retrieval network that included frontoparietal cortices and posterior hippocampus. The second pattern dissociated encoding and retrieval networks. The anterior hippocampus was differentially engaged during encoding. Brain scores, representing whole-brain integrated measures of how strongly an individual recruited a brain network, were correlated with cognitive performance and chronological age. The scores from the general cognitive-control network correlated negatively with episodic memory performance and positively with age. The encoding brain scores, which strongly reflected hippocampal functioning, correlated positively with episodic memory performance and negatively with age. Univariate analyses confirmed that bilateral hippocampus showed the most pronounced activity reduction in older age, and brain structure analyses found that the activity reduction partly related to hippocampus atrophy. Collectively, these findings suggest that age-related structural brain changes underlie age-related reductions in the efficient recruitment of a process-specific encoding network, which cascades into upregulated recruitment of a general cognitive-control network.

Elevated hippocampal resting-state connectivity underlies deficient neurocognitive function in aging

“…We tested the prediction that such negative correlations could be driven by an inability to engage the HC and functionally associated areas during EM tasks by relating within-person HC RSN to task-induced hippocampal (and cortical) recruitment during an EMencoding fMRI task. The magnitude of recruitment of the HC and associated brain networks during encoding has been found to promote EM performance (accuracy during the face-name fMRI task) in this sample (35). We first focused on left and right HC regions (these regions were previously identified to be part of a network that facilitated EM performance during the fMRI task for this sample; table 2 in ref.…”

“…We first focused on left and right HC regions (these regions were previously identified to be part of a network that facilitated EM performance during the fMRI task for this sample; table 2 in ref. 35) that spatially overlapped with the HC RSN. A significant negative correlation was observed between the amplitude of the HC RSN and the degree of task-induced left HC recruitment (Fig.…”

“…Such negative correlations could reflect an inability to flexibly recruit the HC and functionally associated areas during EM task performance due to aberrant hippocampal decoupling (23,24). We tested this prediction by relating the HC RSN, within-person, to HC recruitment during an EM fMRI task (35,36).…”

Thalamic functional connectivity and its association with behavioral performance in older age

“…The recruitment of additional brain regions or increased connectivity between brain regions has been suggested to support the maintenance of cognitive function which would otherwise be disrupted due to age‐related brain changes, such as loss of gray matter or reductions in within‐network connectivity. However, other evidence has shown that increased FC does not always equate to better performance (Geerligs, Saliasi, Maurits, Renken, & Lorist, 2014; Grady et al., 2010; Salami, Eriksson, & Nyberg, 2012). One explanation of this finding could be that older age is associated with reduced specificity of brain networks, which results in less efficient processing, potentially by increasing interference between network activity (Baltes & Lindenberger, 1997) and thus causing deficits in cognition (Antonenko & Floel, 2014).…”

The Neuroprotective Effects of Endurance Training on the Aging Brain

“…These changes emphasize increased activation within the IC and decreased activation relative to baseline in the MPFC and HC that correlate with HR . Importantly, as mentioned previously, these cardiovascular centers are found in regions of the brain most vulnerable to the effects of advancing age , Raz, Lindenberger et al 2005, Nyberg, Salami et al 2010, Salami, Eriksson et al 2012. However, substantial interindividual differences exist in the rate and extent of age-related cortical atrophy leading researchers to examine the potential modifiable risk factors for improved brain health into senescence.…”