Mapping Whole-Brain Nonlinear Structure-Function Dynamics in Aging via Neural Granger Causality

Area of Science:

• Neuroscience
• Brain Aging Research
• Network Science

Background:

• Brain aging involves structural and functional changes, with established links between structural connectivity (SC) and functional connectivity (FC).
• The patterns of structural-functional coupling (SFC) during aging, especially nonlinear interactions, are under-explored.
• Traditional fMRI studies often miss nonlinear causal interactions vital for understanding the aging brain.

Purpose of the Study:

• To investigate whole-brain structural-functional coupling (SFC) using a nonlinear causal approach in aging.
• To compare nonlinear causal SFC between young and older healthy adults, considering sex differences.
• To explore static and dynamic SFC patterns at regional and subnetwork levels.

Main Methods:

• Employed a Nonlinear Granger Causality (NGC) model to assess SFC.
• Included 227 healthy participants (young: 20-35 years; older: 59-77 years), with sex stratification.
• Analyzed both static and dynamic SFC at regional and subnetwork scales.

Main Results:

• Younger adults demonstrated significantly stronger NGC-based SFC than age-matched older adults.
• Males showed a higher proportion of strong SFC connections compared to age-matched females.
• A widespread age-related decline in nonlinear causal coupling was observed, particularly in cognitive control and attention networks.

Conclusions:

• Nonlinear causal relationships are critical for understanding brain network dynamics in aging.
• The findings highlight age-related declines in nonlinear brain coupling, offering insights into cognitive aging mechanisms.
• This nonlinear approach provides a deeper understanding of neurodegenerative processes and age-related cognitive changes.