Prefrontal-parietal effective connectivity during working memory in older adults

Area of Science:

• Neuroscience
• Cognitive Aging
• Neuroimaging

Background:

• Theoretical models suggest age-related changes in frontoparietal neuronal activation during working memory (WM) tasks.
• However, the specific neuronal mechanisms driving these WM load-dependent activation changes in aging are not well understood.

Purpose of the Study:

• To investigate the underlying neuronal mechanisms of age-related working memory decline using effective connectivity analysis.
• To explore how working memory load modulates neural network interactions differently in younger and older adults.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to scan 18 younger and 32 older adults performing an n-back task across three WM load levels.
• Dynamic causal modeling (DCM) with Bayesian Model Selection was applied to analyze effective connectivity within frontoparietal networks.

Main Results:

• Behavioral and fMRI analyses confirmed interactions between age group and WM load.
• Effective connectivity analysis revealed an age- and performance-related reduction in the modulation of connectivity from the dorsolateral prefrontal cortex to the inferior parietal lobule as WM load increased.

Conclusions:

• Age-related working memory decline is associated with impaired WM load-dependent modulation of neuronal top-down control.
• These findings support theoretical models and integrate previous studies on functional changes in the aging brain, highlighting reduced effective connectivity as a key mechanism.