Abstract
The fractal dimension (FD) and spectral frequency of physiological signals are two important indices in the study of physiological functions. The former can extract the intensity and the latter the rhythm of signals embedded in random noise. In this dissertation, a new time-frequency spectral estimation method via spectral distribution function (SDF) that can detect rhythms with high contrast and low error-probability is invoked. This method is based on the fact that SDF includes the discrete components that are characteristic during rhythmic oscillation and, hence, is ideal for analyzing non-stationary signals whose spectral properties evolve over time. It is proved that the proposed method is unbiased and consistent. We also compare it with the conventional time-frequency approaches such as periodogram-based and Fourier methods. Simulation results indicate that the proposed method outperforms periodogram-based and traditional Fourier methods.Secondly, both indices were used to study the involved muscles of bladder and external urethral sphincter (EUS) in the lower urinary tract during the urine storage phase. Eighteen experiments were performed on six intact adult female Wistar rats and then the electromyogram (EMG) of EUS and cystometrogram (CMG) of bladder were analyzed. Results indicated that the EUS did not contain any significant spectral frequencies in the storage phase. Furthermore, its FDs (1.5918±0.0157) indicated that no appreciable amount of signal intensities was observed in the EUS. On the other hand, the bladder exhibited parasympathetic frequency of 8 Hz with signal-to-noise ratio (SNR) = 19.9001 decibel (dB) for group mean, and sympathetic frequency of 19 Hz with SNR = 22.8330 dB for group mean. In addition, its FDs (1.4796±0.0092) indicated relatively persistent intensities during storage as compared to that of EUS (1.5918±0.0157) with statistical significance (P < 0.01). Consequently, we conclude that the EUS is not activated during the phase of storage. It is the bladder that is under the cooperative, not antagonistic, innervations of sympathetic and parasympathetic nervous systems with discernible rhythmic frequencies and intensities.