Neuronal Rhythmicity and its Rate Variability†

Rhythmic surface Electromyographic (sEMG) bursts for which their returns occur at irregular times are analyzed and compared among healthy and injured central nervous systems. The rhythmic electrophysiological activity in the present study has been defined as “Bursting Rate Variability” (BRV) due to the inherent aperiodicity of successive sEMG bursts, which are concomitant with “doublet” waveforms in the D8 subband of the Daubechies 3 wavelet decomposition of the raw signal. A key element in the analysis is the precise timelocalization of D8 doublets that requires a statistical waveform matching between the D8 doublet and the burst in the raw sEMG signal. This study has been conducted over a period of 10 years, in which 7 healthy and 2 unhealthy individuals volunteered and presented a total of ∼8,000 doublets: it was observed that doublets were more prevalent in healthy than unhealthy subjects, and that the probability distribution of return times was best fitted with Normal Mixtures in healthy subjects, compared to the Weibull distribution as the best fit in unhealthy ones based on the corrected Akaike Information Criterion (AICc) for model selection. Finally, the rate in the occurrence of doublets appears to be within 60-88 bursts per minute, suggesting a possible connection between BRV and the heart rate dynamics.