Coupled oscillators: complex but not complicated cardiovascular and brain interactions.

Contemporary measurement techniques enable noninvasive observations of cardiovascular functions, both from the central and peripheral points of view. Cardiovascular dynamics is found to be characterised by several distinct frequency components, and these are present at each site of the system. The corresponding oscillatory processes are mutually dependent via couplings that lead to amplitude/frequency fluctuations of the characteristic peaks. New studies have been initiated to determine the interactions between the cardiovascular oscillations and some of the brain waves. The work will be reviewed and causal relations will be discussed with a special emphasis on detection of the depth of anesthesia.