Fluctuations and synchronization in complex physiological systems

Because complex systems are characterized by inaccessibly many subcomponents that are linked with each other by a variety of interconnections which form a variety of control chains and feedback loops, it is in general difficult to describe their state and dynamics. However, such systems can be approached in a way similar to statistical physics where one aims at the identification of properties evolving from the interplay of many individually unaccessible particles that characterize the macroscopic system. Analogously, the ultimate goal of time series analysis is to identify properties in signals recorded from complex systems that describe the essential dynamics of the whole system, and hence, facilitate a better understanding or modeling of the system. I focus on the complex cardio-vascular system, the complex cardio-respiratory system, and the complex brain system as subsystems of the complex system human. In particular, I introduce, develop, and apply methods to study fluctuations, oscillations, and couplings between different components of these systems. I further illustrate how the results can be exploited for diagnostic tools in human physiology.