The Wigner distribution time frequency analysis algorithm was applied to heart rate variability (HRV) signals during sleep/wakefulness cycles in four 250-350g artificially ventilated neuromuscular blocked (NMB) rats. The HRV spectrum contains three major components, the very low frequency component (0 to 0.25 Hz); the low frequency component (0.25 Hz to 0.8 Hz), and the high frequency component (0.8 Hz to 2.3 Hz). The instantaneous power in the high frequency range of the HRV spectra was quantitatively assessed using the Wigner distribution time frequency algorithm. The time dependent high frequency power of the HRV was clearly higher and lower during the sleep and wakefulness, respectively, and in addition, also varies, with high time resolution, intermediately during the transitional time between the cycles.
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