Coupling and Decoupling between Brain and Body Oscillations

Cross frequency coupling is used intensively to study the cross talk between brain oscillations. In this paper we focus on a special type of frequency coupling between brain and body oscillations, which is reflected by the numerical ratio (r) between two frequencies (m and n; n > m). This approach is motivated by theoretical considerations indicating that an integer relationship (r = n/m = integer number) reflects coupling, whereas an irrational relationship (r = n/m = irrational number) reflects decoupling. We analyzed alpha frequency, heart rate, breathing frequency and spindle frequency from data collected by the SIESTA research group. Our results show a 1:4 frequency relationship between heart rate and breathing frequency both during wakefulness and sleep. During wakefulness we expected but did not find an integer relationship between alpha frequency and heart rate or alpha frequency and breathing frequency. During sleep, we observed an irrational relationship between spindle frequency and heart rate as well as spindle frequency and breathing frequency-suggesting decoupling.