Computational Aspects of the Respiratory Pattern Generator

1994 ◽  
Vol 6 (1) ◽  
pp. 56-68 ◽  
Author(s):  
Allan Gottschalk ◽  
Malcolm D. Ogilvie ◽  
Diethelm W. Richter ◽  
Allan I. Pack
Keyword(s):  
Network Model ◽  
Time Constant ◽  
Respiratory Rhythm ◽  
Network Connectivity ◽  
Pattern Generator ◽  
Continuous Variable ◽  
Respiratory Pattern ◽  
Neural Element ◽  
Respiratory Rhythmogenesis ◽  
Computational Aspects

To help evaluate the hypothesis that the central respiratory rhythm is generated by a network of interacting neurons, a network model of respiratory rhythmogenesis is formulated and examined computationally. The neural elements of the network are driven by tonic inputs and generate a continuous variable representing firing rate. Each neural element in the model can be described by an activation time constant, an adaptation time constant, and a step nonlinearity. Initial network connectivity was based on an earlier proposed model of the central respiratory pattern generator. These connections were adjusted interactively until the model trajectories resembled those observed electrophysiologically. The properties of the resulting network were examined computationally by simulation, determination of the phase resetting behavior of the network oscillator, and examination of the localized eigenstructure of the network. These results demonstrate that the network model can account for a number of diverse physiological observations, and, thus, support the network hypothesis of respiratory rhymogenesis.

Modeling Neural Mechanisms for Genesis of Respiratory Rhythm and Pattern. II. Network Models of the Central Respiratory Pattern Generator

1997 ◽  
Vol 77 (4) ◽  
pp. 2007-2026 ◽  
Author(s):  
Ilya A. Rybak ◽  
Julian F. R. Paton ◽  
James S. Schwaber
Keyword(s):  
Respiratory Rhythm ◽  
Network Models ◽  
Pattern Generator ◽  
Respiratory Pattern ◽  
Respiratory Neurons ◽  
Two Phase ◽  
Firing Patterns ◽  
Three Phase ◽  
Phase Models ◽  
Respiratory Phases

Rybak, Ilya A., Julian F. R. Paton, and James S. Schwaber. Modeling neural mechanisms for genesis of respiratory rhythm and pattern. II. Network models of the central respiratory pattern generator. J. Neurophysiol. 77: 2007–2026, 1997. The present paper describes several models of the central respiratory pattern generator (CRPG) developed employing experimental data and current hypotheses for respiratory rhythmogenesis. Each CRPG model includes a network of respiratory neuron types (e.g., early inspiratory; ramp inspiratory; late inspiratory; decrementing expiratory; postinspiratory; stage II expiratory; stage II constant firing expiratory; preinspiratory) and simplified models of lung and pulmonary stretch receptors (PSR), which provide feedback to the respiratory network. The used models of single respiratory neurons were developed in the Hodgkin-Huxley style as described in the previous paper. The mechanism for termination of inspiration (the inspiratory off-switch) in all models operates via late-I neuron, which is considered to be the inspiratory off-switching neuron. Several two- and three-phase CRPG models have been developed using different accepted hypotheses of the mechanism for termination of expiration. The key elements in the two-phase models are the early-I and dec-E neurons. The expiratory off-switch mechanism in these models is based on the mutual inhibitory connections between early-I and dec-E and adaptive properties of the dec-E neuron. The difference between the two-phase models concerns the mechanism for ramp firing patterns of E2 neurons resulting either from the intrinsic neuronal properties of the E2 neuron or from disinhibition from the adapting dec-E neuron. The key element of the three-phase models is the pre-I neuron, which acts as the expiratory off-switching neuron. The three-phase models differ by the mechanisms used for termination of expiration and for the ramp firing patterns of E2 neurons. Additional CRPG models were developed employing a dual switching neuron that generates two bursts per respiratory cycle to terminate both inspiration and expiration. Although distinctly different each model generates a stable respiratory rhythm and shows physiologically plausible firing patterns of respiratory neurons with and without PSR feedback. Using our models, we analyze the roles of different respiratory neuron types and their interconnections for the respiratory rhythm and pattern generation. We also investigate the possible roles of intrinsic biophysical properties of different respiratory neurons in controlling the duration of respiratory phases and timing of switching between them. We show that intrinsic membrane properties of respiratory neurons are integrated with network properties of the CRPG at three hierarchical levels: at the cellular level to provide the specific firing patterns of respiratory neurons (e.g., ramp firing patterns); at the network level to provide switching between the respiratory phases; and at the systems level to control the duration of inspiration and expiration under different conditions (e.g., lack of PSR feedback).

scholarly journals Spike synchronization is population specific in the respiratory pattern generator

2009 ◽  
Vol 10 (Suppl 1) ◽  
pp. P248
Author(s):  
David M Baekey ◽  
Thomas E Dick ◽  
Roberto F Galán
Keyword(s):  
Pattern Generator ◽  
Respiratory Pattern

Ventilatory responses to cooling the ventrolateral medullary surface of awake and anesthetized goats

1995 ◽  
Vol 78 (1) ◽  
pp. 247-257 ◽  
Author(s):  
P. J. Ohtake ◽  
H. V. Forster ◽  
L. G. Pan ◽  
T. F. Lowry ◽  
M. J. Korducki ◽  
...  
Keyword(s):  
Pulmonary Ventilation ◽  
Respiratory Rhythm ◽  
Respiratory Neurons ◽  
Ventrolateral Medulla ◽  
Arterial Pco2 ◽  
Respiratory Rhythmogenesis ◽  
Ventilatory Responses ◽  
Anesthesia Breathing ◽  
A Site ◽  
Caudal Area

The ventrolateral medulla (VLM) has been reported to be important as a source of tonic facilitation of dorsal respiratory neurons and as a site critical for respiratory rhythmogenesis. We investigated these theories in awake and anesthetized goats (n = 13) by using chronically implanted thermodes to create reversible neuronal dysfunction at superficial VLM sites between the first hypoglossal rootlet and the pontomedullary junction (area M (rostral) and area S). During halothane anesthesia (arterial PCO2 = 57.4 +/- 4.5 Torr), bilateral cooling (thermode temperature = 20 degrees C) of 60–100% of areas M and S for 30 s produced a sustained apnea (46 +/- 4 s) that lasted beyond the period of cooling. While the animals were awake (arterial PCO2 = 36.0 +/- 1.9 Torr), cooling the identical region in the same goats resulted in a decrease (approximately 50%) in pulmonary ventilation, with a brief apnea seen only in one goat. Reductions in both tidal volume and frequency were observed. Qualitatively similar responses were obtained when cooling caudal area M-rostral area S and rostral area M, but the responses were less pronounced. Minimal effects were seen in response to cooling caudal area S. During anesthesia, breathing is critically dependent on superficial VLM neurons, whereas in the awake state these neurons are not essential for the maintenance of respiratory rhythm. Our data are consistent with these superficial VLM neuronal regions providing tonic facilitation to more dorsal respiratory neurons in both the anesthetized and awake states.

scholarly journals Site-specific effects on respiratory rhythm and pattern of ibotenic acid injections in the pontine respiratory group of goats

2010 ◽  
Vol 109 (1) ◽  
pp. 171-188 ◽  
Author(s):  
J. M. Bonis ◽  
S. E. Neumueller ◽  
K. L. Krause ◽  
T. Kiner ◽  
A. Smith ◽  
...  
Keyword(s):  
Pulmonary Ventilation ◽  
Respiratory Rhythm ◽  
Ibotenic Acid ◽  
Pattern Generation ◽  
Respiratory Pattern ◽  
Breathing Patterns ◽  
Site Specific ◽  
Specific Effects ◽  
Tegmental Nuclei ◽  
Pontine Respiratory Group

To probe further the contributions of the rostral pons to eupneic respiratory rhythm and pattern, we tested the hypothesis that ibotenic acid (IA) injections in the pontine respiratory group (PRG) would disrupt eupneic respiratory rhythm and pattern in a site- and state-specific manner. In 15 goats, cannulas were bilaterally implanted into the rostral pontine tegmental nuclei (RPTN; n = 3), the lateral (LPBN; n = 4) or medial parabrachial nuclei (MPBN; n = 4), or the Kölliker-Fuse nucleus (KFN; n = 4). After recovery from surgery, 1- and 10-μl injections (1 wk apart) of IA were made bilaterally through the implanted cannulas during the day. Over the first 5 h after the injections, there were site-specific ventilatory effects, with increased ( P < 0.05) breathing frequency in RPTN-injected goats, increased ( P < 0.05) pulmonary ventilation (V̇i) in LPBN-injected goats, no effect ( P < 0.05) in MPBN-injected goats, and a biphasic V̇i response ( P < 0.05) in KFN-injected goats. This biphasic response consisted of a hyperpnea for 30 min, followed by a prolonged hypopnea and hypoventilation with marked apneas, apneusis-like breathing patterns, and/or shifts in the temporal relationships between inspiratory flow and diaphragm activity. In the awake state, 10–15 h after the 1-μl injections, the number of apneas was greater ( P < 0.05) than during other studies at night. However, there were no incidences of terminal apneas. Breathing rhythm and pattern were normal 22 h after the injections. Subsequent histological analysis revealed that for goats with cannulas implanted into the KFN, there were nearly 50% fewer neurons ( P < 0.05) in all three PRG subnuclei than in control goats. We conclude that in awake goats, 1) IA injections into the PRG have site-specific effects on breathing, and 2) the KFN contributes to eupneic respiratory pattern generation.

scholarly journals Synaptic propagation in neuronal networks with finite-support space dependent coupling

2020 ◽  
Author(s):  
Ricardo Erazo Toscano ◽  
Remus Osan
Keyword(s):  
Time Constant ◽  
Sensory Processing ◽  
Traveling Waves ◽  
Traveling Wave ◽  
Neuronal Networks ◽  
Evolution Equations ◽  
Network Connectivity ◽  
Space Constant ◽  
The Stability ◽  
The Brain

1AbstractTraveling waves of electrical activity are ubiquitous in biological neuronal networks. Traveling waves in the brain are associated with sensory processing, phase coding, and sleep. The neuron and network parameters that determine traveling waves’ evolution are synaptic space constant, synaptic conductance, membrane time constant, and synaptic decay time constant. We used an abstract neuron model to investigate the propagation characteristics of traveling wave activity. We formulated a set of evolution equations based on the network connectivity parameters. We numerically investigated the stability of the traveling wave propagation with a series of perturbations with biological relevance.

scholarly journals Maturation of the Mammalian Respiratory System

1999 ◽  
Vol 79 (2) ◽  
pp. 325-360 ◽  
Author(s):  
Gérard Hilaire ◽  
Bernard Duron
Keyword(s):  
Respiratory Activity ◽  
Respiratory Rhythm ◽  
Ventrolateral Medulla ◽  
Pacemaker Neurons ◽  
Inhibitory Processes ◽  
Respiratory Rhythmogenesis ◽  
Respiratory Network ◽  
Network Functions

In this review, the maturational changes occurring in the mammalian respiratory network from fetal to adult ages are analyzed. Most of the data presented were obtained on rodents using in vitro approaches. In gestational day 18 (E18) fetuses, this network functions but is not yet able to sustain a stable respiratory activity, and most of the neonatal modulatory processes are not yet efficient. Respiratory motoneurons undergo relatively little cell death, and even if not yet fully mature at E18, they are capable of firing sustained bursts of potentials. Endogenous serotonin exerts a potent facilitation on the network and appears to be necessary for the respiratory rhythm to be expressed. In E20 fetuses and neonates, the respiratory activity has become quite stable. Inhibitory processes are not yet necessary for respiratory rhythmogenesis, and the rostral ventrolateral medulla (RVLM) contains inspiratory bursting pacemaker neurons that seem to constitute the kernel of the network. The activity of the network depends on CO2 and pH levels, via cholinergic relays, as well as being modulated at both the RVLM and motoneuronal levels by endogenous serotonin, substance P, and catecholamine mechanisms. In adults, the inhibitory processes become more important, but the RVLM is still a crucial area. The neonatal modulatory processes are likely to continue during adulthood, but they are difficult to investigate in vivo. In conclusion, 1) serotonin, which greatly facilitates the activity of the respiratory network at all developmental ages, may at least partly define its maturation; 2) the RVLM bursting pacemaker neurons may be the kernel of the network from E20 to adulthood, but their existence and their role in vivo need to be further confirmed in both neonatal and adult mammals.

Effects on respiratory pattern of focal cooling in the medulla of the dog

1988 ◽  
Vol 65 (5) ◽  
pp. 2004-2010 ◽  
Author(s):  
M. Adams ◽  
T. Chonan ◽  
N. S. Cherniack ◽  
C. von Euler
Keyword(s):  
Respiratory Rhythm ◽  
Nucleus Ambiguus ◽  
Respiratory Pattern ◽  
Respiratory Drive ◽  
Timing Effect ◽  
Diaphragm Electrical Activity ◽  
Inspiratory Activity ◽  
Ventral Medullary Surface ◽  
Focal Cooling

Studies in cats have shown that, in addition to respiratory neuron groups in the dorsomedial (DRG) and ventrolateral (VRG) medulla, neural structures in the most ventral medullary regions are important for the maintenance of respiratory rhythm. The purpose of this study was to determine whether a similar superficially located ventral region was present in the dog and to assess the role of each of the other regions in the canine medulla important in the control of breathing, in 20 anesthetized, vagotomized, and artificially ventilated dogs, a cryoprobe was used to cool selected regions of the medulla to 15-20 degrees C. Respiratory output was determined from phrenic nerve or diaphragm electrical activity. Cooling in or near the nucleus of the solitary tract altered timing and produced little change in the amplitude or rate of rise of inspiratory activity; lengthening of inspiratory time was the most common timing effect observed. Cooling in ventrolateral regions affected the amplitude and rate of rise of respiratory activity. Depression of neural tidal volume and apnea could be produced by unilateral cooling in two ventrolateral regions: 1) near the nucleus ambiguus and nucleus para-ambiguus and 2) just beneath the ventral medullary surface. These findings indicate that in the dog dorsomedial neural structures influence respiratory timing, whereas more ventral structures are important to respiratory drive.

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