Learning Graph Filters for Structure-Function Coupling based Hub Node Identification

TL;DR

This paper introduces GraFHub, a graph signal processing framework that combines structural and functional brain data to more accurately identify hub nodes, improving upon traditional methods that use only functional connectivity.

Contribution

It presents a novel GSP-based method that models functional activity as graph signals on structural connectivity for hub detection, incorporating structure-function coupling.

Findings

Effective hub detection on simulated data

Successful application to HCP rs-fMRI data

Outperforms traditional centrality-based methods

Abstract

Over the past two decades, tools from network science have been leveraged to characterize the organization of both structural and functional networks of the brain. One such measure of network organization is hub node identification. Hubs are specialized nodes within a network that link distinct brain units corresponding to specialized functional processes. Conventional methods for identifying hub nodes utilize different types of centrality measures and participation coefficient to profile various aspects of nodal importance. These methods solely rely on the functional connectivity networks constructed from functional magnetic resonance imaging (fMRI), ignoring the structure-function coupling in the brain. In this paper, we introduce a graph signal processing (GSP) based hub detection framework that utilizes both the structural connectivity and the functional activation to identify hub nodes. The proposed framework models functional activity as graph signals on the structural connectivity. Hub nodes are then detected based on the premise that hub nodes are sparse, have higher level of activity compared to their neighbors, and the non-hub nodes' activity can be modeled as the output of a graph-based filter. Based on these assumptions, an optimization framework, GraFHub, is formulated to learn the coefficients of the optimal polynomial graph filter and detect the hub nodes. The proposed framework is evaluated on both simulated data and resting state fMRI (rs-fMRI) data from Human Connectome Project (HCP).