Electroencephalographic frequencies associated with heart changes in RR interval variability during paradoxical sleep.

Brain stem autonomic oscillators, hypothalamic and cortico-frontal centre, entrained by baroreceptor input, have been proposed as the control system of the heart rhythm. Recent reported results in animals suggested that the hippocampal theta waves might also participate as a heart rate modulator. A temporal correlation among the firing of neurons in the medulla, the R-wave of the electrocardiogram, hippocampal units, and theta rhythm was reported in guinea pigs. Our present aim is the analysis of the human electroencephalogram (EEG) frequencies power associated with changes in RR interval variability epochs during paradoxical sleep. We hypothesized that the differences in the human balance of the autonomic centres in sleep would be represented in the central nervous system by changes in the low-frequency EEG bands power. The heart rate analysis included 4 s windows, i.e., not considering the lowest component. The result was a consistent increment in the power of the paradoxical sleep delta and theta EEG bands during physiologic high heart RR interval variability epochs; no changes in the EEG bands power were found in the previous windows. The temporal correlation of heart RR interval variability and delta-theta EEG bands increases is proposed to represent a functional interaction when the control of specific centres fails or decreases during paradoxical sleep, a period mainly operating in an "open-loop" fashion.