Fig. 7

Power spectra of the R–R intervals of control rabbits (n = 6) before and after bilateral supra-nodose vagotomy. a Before vagotomy, the prominent components of the power spectral density (PSD) occurred in the very-low- (< 0.2 Hz) and high- (0.8–1.7 Hz) frequency bands. b After vagotomy, the power of the very-low-frequency components (< 0.2 Hz) increased, while the high-frequency band decreased. c The mean power spectrum of vagotomized rabbits (filled circles, continuous line) increased in the very-low frequency band compared to that before vagotomy (empty circles), while the power in the high frequency band decreased, nearly absent between 0.8 and 1.7 Hz compared to that before vagotomy. Left inset: mean power spectra of the high-frequency band (0.8–2.0 Hz). Right inset: mean values, in standardized units (S.U.), of low frequency (LF), high frequency (HF) and LF/HF ratio in control conditions (empty bars) and after bilateral vagotomy (filled bars). *Significantly larger than intact condition; p < 0.05. Dispersion bars: SEM. PSD power spectral density