Bispectral analysis of complex patterns of sympathetic nerve
discharge.
Gebber, Gerard L., Sheng Zhong, and Yvan Paitel.
Departments of Pharmacology/Toxicology and Physiology, Michigan
State University, East Lansing, MI 48824
APStracts 3:0088R, 1996.
Bispectral analysis was used to demonstrate quadratic nonlinear
coupling (i.e., phase-locking) of different frequency components in
inferior cardiac sympathetic nerve discharge (SND) of urethan
-anesthetized cats. The complex patterns of SND analyzed included
mixtures of a) the cardiac-related and 10-Hz rhythms, b) the 10-Hz
rhythm and irregular 2- to 6-Hz oscillations, and c) the 10-Hz rhythm
and a lower frequency noncardiac-related rhythm near 4 Hz. In some
cases, the bicoherence function (normalized bispectrum) showed no
phase-locking of these frequency components. Cases of nil bicoherence
are equated with linear superposition of frequency components which
implies the existence of multiple and noninteractive central
circuits. Increased complexity of SND was observed in other cases, as
evidenced by significant phase-locking of different frequency
components with or without frequency-locking. Frequency-locking
(higher frequency rhythm is a multiple of lower) was confirmed by
constructing Lissajous orbital plots showing covariation of voltages
in selectively filtered bands of SND. We equate frequency-locking
with nonlinear coupling of the central generators of different
sympathetic nerve rhythms, and phase-locking without frequency
-locking possibly with nonlinearities arising at levels below
noncoupled central rhythm generators.
Received 12 October 1995; accepted in final form 26 February
1996.
APS Manuscript Number R646-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 20 March 96