Physiologic systems dynamics, coupling and network interactions across the sleep-wake cycle

We review recent progress in understanding fundamental aspects of physiologic regulation during wake and sleep based on modern data-driven, analytic, and computational approaches with focus on the complex dynamics of individual physiological systems, their transient forms of coupling, and the role of network interactions among physiological systems in generating states and functions at the integrated organism level. The presented empirical findings indicate that sleep-wake and circadian cycles do not simply modulate basic physiologic functions by generating rhythms with a fixed periodicity but influence physiological systems dynamics simultaneously over a broad range of time scales. Furthermore, transitions across physiologic states are characterized by modulation in the strength of physiologic coupling and by hierarchical reorganization in the network of interactions among physiological systems, indicating high-network flexibility in response to change in physiologic regulation. We underscore the importance of novel, integrative approaches to investigate physiological dynamics of individual systems across multiple scales and to quantify emergent global behaviors of networks of physiologic interactions to comprehensively understand physiologic state and function.