Analysis of Optical Brain Signals Using Connectivity Graph Networks

Abstract

Graph network analysis (GNA) showed a remarkable role for understanding brain functions, but its application is mainly nar-rowed to fMRI research. Connectivity analysis (CA) is introduced as a signal-to-graph mapping in a time-causality framework. In this paper, we investigate the application of GNA/CA in fNIRS. To solve the inher-ent challenges of using CA, we also propose a novel metric: a maximum cross-lag magnitude (MCLM) that eÿciently extracts major causality in-formation. We tested MCLM in four types of cognitive activities (mental arithmetic, motor imagery, word generation, and brain workload) from 55 participants. CA/MCLM showed a compelling modeling capacity and re-vealed unexpected cross-subject network patterns. We found that motion imagery and mental arithmetic share a background network structure, and that the right prefrontal cortex, in AFp8, is an invariable destina-tion for information flows in every stimuli and participant. Therefore, CA/MCLM-fNIRS showed potential for its use along with fNIRS in clin-ical studies.