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ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Time-frequency coherence analysis of phrenic and hypoglossal activity in the decerebrate rat during eupnea, hyperpnea, and gasping

Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware

Submitted 28 March 2006 ; accepted in final form 27 June 2006

Fast respiratory rhythms include medium- (MFO) and high-frequency oscillations (HFO), which are much faster than the fundamental breathing rhythm. According to previous studies, HFO is characterized by high coherence (Coh) in phrenic (Ph) nerve activity, thereby providing a means of distinguishing between these two types of oscillations. Changes in Coh between the Ph and hypoglossal (XII) nerves during the transition from normal eupnic breathing to gasping have not been characterized. Experiments were performed on nine unanesthetized, chemo- and barodenervated, decerebrate adult rats, in which sustained asphyxia elicited hyperpnea and gasping. A gated time-frequency Coh analysis was developed and applied to whole Ph and medial XII nerve recordings. The results showed dynamic Ph-Ph Coh during eupnea, including MFO and HFO. XII-XII Coh during eupnea was broadband and included four distinct peaks, with low-frequency Coh dominating the epochs preceding the onset of Ph activity. During gasping, only MFO-peaks were present in Ph-Ph Coh. Bilateral XII activity showed a significant reduction in Coh and a shift toward lower frequencies during gasping. In contrast, contralateral Ph-XII Coh progressively increased during state changes from eupnea to gasping, a tendency mirrored in the startup part of the Ph activity. These data suggest significant hypoxia/hypercapnia-induced alterations in synchronization between respiratory outputs during the transition from eupnea to gasping, reflecting a reconfiguration of the respiratory network and/or alterations in the circuitry associated with the motor pools, including dynamic coupling between outputs.

respiratory patterns; zero-interval subtraction analysis; motor coupling; network plasticity; rhythmogenesis

This article has been cited by other articles:

				V. Marchenko and R. F. Rogers GABAAergic and Glycinergic Inhibition in the Phrenic Nucleus Organizes and Couples Fast Oscillations in Motor Output J Neurophysiol, April 1, 2009; 101(4): 2134 - 2145. [Abstract] [Full Text] [PDF]

				V. Marchenko and R. F. Rogers Temperature and state dependence of dynamic phrenic oscillations in the decerebrate juvenile rat Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2007; 293(6): R2323 - R2335. [Abstract] [Full Text] [PDF]