Different interference patterns among spontaneous low and high frequency oscillations and forced ventilation in sympathetic outflow

In the sympathetic outflow directed to the heart of decerebrate artificially ventilated cats, non-linear interferences among spontaneous low frequency waves, (LF, approx. 0.1 Hz) related to vasomotor control, an high frequency (HF, approx. 0.3 Hz) from respiratory centers, and forced ventilation (at 0.3 Hz) were investigated. Various methods were tested for the simultaneous processing of sympathetic activity (Sy) and ventilation (V). Time-space separation plot (TSSP) and frequency tracking locus (FTL) were used to detect phase locking (PL) and quasiperiodicity (QP). Deterministic patterns hidden in aperiodic data were also searched for. In comparison to control (n=17), sympathetic activation (inferior vena cava occlusion, n=17) increased PL of LF to V, while the reverse was observed during sympathetic inhibition (aortic constriction, n=13). After spinal section, (n=26) aperiodicity with intermittency was found.