Mediating role of feeder connections in the relationship between brain network efficiency and episodic memory in...

Advances in connectomics and network neuroscience have opened new avenues for the in-depth study of complex brain networks. However, the mechanisms of brain neuroplasticity associated with fiber connections ("lines") and networks ("planes") for the integration of episodic memory remain largely unknown. This study aimed to: (1) analyze the topological properties of individual structural networks using multi-shell, multi-tissue, constrained spherical deconvolution (MSMT-CSD) based on high-angular resolution diffusion imaging (HARDI) data and (2) explore the mediation among network efficiency, the three types of connections in individual structural networks, and episodic memory.

This case-control study included 29 amnestic mild cognitive impairment (aMCI) patients and 29 age-, sex-, and education-matched healthy controls. Participants underwent comprehensive neuropsychological assessments, and MRI scans to collect HARDI data and T1-weighted sequence data. Individual structural networks were constructed, followed by rich-club, network, and mediation analysis at group-level.

Rich-club analysis indicated no significant difference in rich-club connections, but significant reductions in feeder and local connections among aMCI patients. Global property analysis showed significant decreased global efficiency, local efficiency, clustering coefficient, γ, and σ, with an increased characteristic path length. Nodal property analysis showed a significant decrease in betweenness centrality in the left anterior cingulate and paracingulate gyri. Mediation analysis demonstrated that feeder connections mediate the relationship between network efficiency and episodic memory (indirect effect β = 0.142, 95 % confidence interval (CI) = [0.002, 0.311]).

Utilization of advanced imaging mathematical algorithms such as the MMST-CSD elucidates the crucial role of fiber connections ("lines") and network characteristics ("planes") in the memory process. Notably, our findings showed that feeder connections in the white matter structural network played a mediating role in linking network efficiency to episodic memory.

These findings provide new potential targets for neuromodulation treatments and contribute to closing gaps in current research on brain network contributions to cognitive functions.