The presence of coherence in sympathetic and phrenic activities in a developing mammal.

To determine whether are development changes in the baroreceptor and central respiratory modulation of sympathetic activity, we used ordinary and partial coherence spectral analyses on cervical and splanchnic sympathetic activity in swine 1-36 days old. Removal of baroreceptor influences from cervical sympathetic and splanchnic spectra using partialization shows that 3-6 Hz peaks are due to baroreceptors since coherence decreased in > 19 days old while remaining unchanged in < 2 weeks old piglets. The 8-12 Hz band (present in normal coherence after 21 days) was revealed in piglets < 14 days old after removal of respiratory modulation by partialization; similarly increased coherence was also observed in the 16-18 Hz band through 3 weeks. Thus, use of partial power and coherency is a useful tool for unmasking the complex relationship found in developing SYMP outflows. These results suggest that there is a period of reorganization within the SYMP rhythm generating circuits, which may be essential for normal development.