Burst‐To‐Burst Variability In Spectral Activity Underlying Diaphragm Electromyogram (EMG) Bursts In Anesthetized C57BL/6 Mice In Vivo

Abstract

Previous work from our laboratory using time-frequency spectral analysis has suggested that the spectral characteristics of inspiratory motor output in mice are highly dynamic. In that work, burst-to-burst variability analysis was performed on 10-s segments of diaphragm EMG activity recorded from urethane-anesthetized adult C57BL/6 mice. Although short-term burst-to-burst variability was reported, the extent of long-term burst-to-burst variability in this model requires clarification. Here, we characterize the burst-to-burst variability of temporal and spectral features for basal diaphragm EMG bursts recorded from 6 mice using Poincaré plot analysis of breath n vs. n+1 on 5-min time segments, which contain ~750-1245 bursts. Analyses on temporal parameters (i.e., TI, TE, burst frequency, area) show a high degree of correlation between adjacent bursts, suggesting a small degree of both short- and long-term burst-to-burst variability. For spectral characteristics, power of medium frequency oscillations (MFO) appeared to be more deterministic than that seen in the high (HFO) or upper-high (UHFO) ranges, with low power MFO peaks being followed primarily by other low power MFO peaks. In contrast, power for the HFO and UHFO peaks were widely dispersed, indicating aperiodic behavior. Interestingly, however, there were some HFO peaks exhibiting low power that seemed to predict subsequent low power HFO peaks. These data are among the first to quantify short-term and long-term burst-to-burst variability of spectral features using mathematical fits to Poincaré plots, and demonstrate new insight into dynamic variability in the fast oscillatory rhythms inherent in inspiratory motor discharges. Supported by NS045321