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

Area of Science:

• Neuroscience
• Cognitive Aging
• Neuroimaging

Background:

• The brain remains active during rest, with identified resting-state networks like the default mode network (DMN).
• Age-related changes in the DMN and hippocampus (HC) functional architecture may predict memory decline.
• The precise nature of DMN-HC alterations in aging and memory deficits is not fully understood.

Purpose of the Study:

• To investigate age-related alterations in the functional connectivity between the default mode network (DMN) and the hippocampus (HC).
• To examine the relationship between these alterations, white matter integrity, and episodic memory performance.
• To explore how resting-state HC connectivity affects neural recruitment during memory encoding.

Main Methods:

• Utilized resting-state and task-based functional MRI (fMRI) data from 339 participants aged 25-80.
• Analyzed functional connectivity within the DMN and between the HC and cortical regions.
• Assessed white matter integrity (fornix) and episodic memory performance (cross-sectional and longitudinal).

Main Results:

• Observed age-related decreases in DMN connectivity, but increased internal HC connectivity.
• Found reduced HC-cortical connectivity with aging, partly linked to fornix white matter integrity decline.
• Elevated resting HC connectivity correlated with poorer episodic memory and reduced neural recruitment during memory encoding.

Conclusions:

• Aging disrupts cortico-hippocampal functional connectivity, leading to a more isolated HC at rest.
• This increased resting HC connectivity is associated with memory deficits and impaired hippocampal function during active memory processing.
• Findings suggest a model where age-related decoupling of the HC contributes to mnemonic processing deficits.