A phase-shifting anterior-posterior network organizes global phase relations

Abstract

AbstractPrior research has identified a variety of task-dependent networks that form through inter-regional phase-locking of oscillatory activity as neural correlates of specific behaviors. Despite ample knowledge of task-specific functional networks, general rules governing global phase relations have not been investigated. In order to discover such general rules, we focused on phase modularity, measured as the degree to which global phase relations in EEG comprised distinct synchronized clusters interacting with one another at large phase lags. Synchronized clusters were detected with a standard community-detection algorithm, and the level of phase modularity was quantified by the index q. Our findings suggest that phase modularity is functionally consequential since (1) temporal distribution of q was invariant across a broad range of frequencies (3-50 Hz examined) and behavioral conditions (resting with the eyes closed or watching a silent nature video), and (2) neural interactions (measured as power correlations) in beta-to-gamma bands consistently increased in high-modularity states. Notably, we found that the mechanism controlling phase modularity is remarkably simple. A network comprising anterior-posterior long-distance connectivity coherently shifted phase relations from low-angles (|Δθ| < π/4) in low-modularity states (bottom 5% in q) to high-angles (|Δθ| > 3π/4) in high-modularity states (top 5% in q), accounting for fluctuations in phase modularity. This anterior-posterior network likely plays a fundamental functional role as it controls phase modularity across a broad range of frequencies and behavioral conditions. These results may motivate future investigations into the functional roles of phase modularity as well as the anterior-posterior network that controls it.