scholarly journals The neuromuscular transform in a single segment of a segmented heart tube

2020 ◽  
Vol 124 (3) ◽  
pp. 914-929
Author(s):  
Angela Wenning ◽  
Young Rim Chang ◽  
Brian J. Norris ◽  
Ronald L. Calabrese
Keyword(s):  
Relaxation Time ◽  
Central Pattern Generator ◽  
Motor Neurons ◽  
Pattern Generator ◽  
Spike Frequency ◽  
Burst Duration ◽  
Cycle Period ◽  
Heart Tube ◽  
Single Segment ◽  
Over Time

Moving blood through the segmented heart tubes of leeches requires sequential constrictions driven by motor neurons controlled by a central pattern generator. In a single heart segment, we varied stimuli to explore the neuromuscular transform. Decreasing the cycle period, e.g., to increase volume pumped over time, without altering motor burst duration and intraburst spike frequency shortens relaxation time and decreases amplitude. The likely strategy to preserve constriction amplitude is to shorten burst duration while increasing spike frequency.

Gating of Afferent Input by a Central Pattern Generator

1999 ◽  
Vol 81 (2) ◽  
pp. 950-953 ◽  
Author(s):  
Ralph A. DiCaprio
Keyword(s):  
Central Pattern Generator ◽  
Sensory Input ◽  
Motor Pattern ◽  
Pattern Generator ◽  
Afferent Input ◽  
Inhibitory Input ◽  
Cycle Period ◽  
Intracellular Recordings ◽  
Afferent Fibers ◽  
Sufficient Magnitude

Gating of afferent input by a central pattern generator. Intracellular recordings from the sole proprioceptor (the oval organ) in the crab ventilatory system show that the nonspiking afferent fibers from this organ receive a cyclic hyperpolarizing inhibition in phase with the ventilatory motor pattern. Although depolarizing and hyperpolarizing current pulses injected into a single afferent will reset the ventilatory motor pattern, the inhibitory input is of sufficient magnitude to block afferent input to the ventilatory central pattern generator (CPG) for ∼50% of the cycle period. It is proposed that this inhibitory input serves to gate sensory input to the ventilatory CPG to provide an unambiguous input to the ventilatory CPG.

Detailed Model of Intersegmental Coordination in the Timing Network of the Leech Heartbeat Central Pattern Generator

2004 ◽  
Vol 91 (2) ◽  
pp. 958-977 ◽  
Author(s):  
Sami H. Jezzini ◽  
Andrew A. V. Hill ◽  
Pavlo Kuzyk ◽  
Ronald L. Calabrese
Keyword(s):  
Central Pattern Generator ◽  
Pattern Generator ◽  
Living System ◽  
Cycle Period ◽  
Intersegmental Coordination ◽  
Experimental Conditions ◽  
Detailed Model ◽  
Distributed Structure ◽  
Synaptic Interactions ◽  
Oscillatory Neuronal Networks

To address the general problem of intersegmental coordination of oscillatory neuronal networks, we have studied the leech heartbeat central pattern generator. The core of this pattern generator is a timing network that consists of two segmental oscillators, each of which comprises two identified, reciprocally inhibitory oscillator interneurons. Intersegmental coordination between the segmental oscillators is mediated by synaptic interactions between the oscillator interneurons and identified coordinating interneurons. The small number of neurons (8) and the distributed structure of the timing network have made the experimental analysis of the segmental oscillators as discrete, independent units possible. On the basis of this experimental work, we have made conductance-based models to explore how intersegmental phase and cycle period are determined. We show that although a previous simple model, which ignored many details of the living system, replicated some essential features of the living system, the incorporation of specific cellular and network properties is necessary to capture the behavior of the system seen under different experimental conditions. For example, spike frequency adaptation in the coordinating interneurons and details of asymmetries in intersegmental connectivity are necessary for replicating driving experiments in which one segmental oscillator was injected with periodic current pulses to entrain the activity of the entire network. Nevertheless, the basic mechanisms of phase and period control demonstrated here appear to be very general and could be used by other networks that produce coordinated segmental motor outflow.

Long-Term Expression of Two Interacting Motor Pattern-Generating Networks in the Stomatogastric System of Freely Behaving Lobster

1998 ◽  
Vol 79 (3) ◽  
pp. 1396-1408 ◽  
Author(s):  
Stefan Clemens ◽  
Denis Combes ◽  
Pierre Meyrand ◽  
John Simmers
Keyword(s):  
Motor Neurons ◽  
Motor Pattern ◽  
Burst Duration ◽  
Cycle Period ◽  
Gastric Mill ◽  
Pyloric Network ◽  
Freely Behaving ◽  
Stomatogastric System

Clemens, Stefan, Denis Combes, Pierre Meyrand, and John Simmers. Long-term expression of two interacting motor pattern-generating networks in the stomatogastric system of freely behaving lobster. J. Neurophysiol. 79: 1396–1408, 1998. Rhythmic movements of the gastric mill and pyloric regions of the crustacean foregut are controlled by two stomatogastric neuronal networks that have been intensively studied in vitro. By using electromyographic recordings from the European lobster, Homarus gammarus, we have monitored simultaneously the motor activity of pyloric and gastric mill muscles for ≤3 mo in intact and freely behaving animals. Both pyloric and gastric mill networks are almost continuously active in vivo regardless of the presence of food. In unfed resting animals kept under “natural-like” conditions, the pyloric network expresses the typical triphasic pattern seen in vitro but at considerably slower cycle periods (2.5–3.5 s instead of 1–1.5 s). Gastric mill activity occurs at mean cycle periods of 20–50 s compared with 5–10 s in vitro but may suddenly stop for up to tens of minutes, then restart without any apparent behavioral reason. When conjointly active, the two networks express a strict coupling that involves certain but not all motor neurons of the pyloric network. The posterior pyloric constrictor muscles, innervated by a total of 8 pyloric (PY) motor neurons, are influenced by the onset of each gastric mill medial gastric/lateral gastric(MG/LG) neuron powerstroke burst, and for one cycle, PY neuron bursts may attain >300% of their mean duration. However, the duration of activity in the lateral pyloric constrictor muscle, innervated by the unique lateral pyloric (LP) motor neuron, remains unaffected by this perturbation. During this period after gastric perturbation, LP neuron and PY neurons thus express opposite burst-to-period relationships in that LP neuron burst duration is independent of the ongoing cycle period, whereas PY neuron burst duration changes with period length. In vitro the same type of gastro-pyloric interaction is observed, indicating that it is not dependent on sensory inputs. Moreover, this interaction is intrinsic to the stomatogastric ganglion itself because the relationship between the two networks persists after suppression of descending inputs to the ganglion. Intracellular recordings reveal that thisgastro-pyloric interaction originates from the gastric MG and LG neurons of the gastric network, which inhibit the pyloric pacemaker ensemble. As a consequence, the pyloric PY neurons, which are inhibited by the pyloric dilator (PD) neurons of the pyloric pacemaker group, extend their activity during the time that PD neuron is held silent. Moreover, there is evidence for a pyloro-gastric interaction, apparently rectifying, from the pyloric pacemakers back to the gastric MG/LG neuron group.

scholarly journals Output variability across animals and levels in a motor system

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Angela Wenning ◽  
Brian J Norris ◽  
Cengiz Günay ◽  
Daniel Kueh ◽  
Ronald L Calabrese
Keyword(s):  
Life History ◽  
Central Pattern Generator ◽  
Motor Neurons ◽  
Motor System ◽  
Motor Pattern ◽  
Pattern Generator ◽  
Phase Relations ◽  
The Other ◽  
Output Variability ◽  
Rhythmic Behaviors

Rhythmic behaviors vary across individuals. We investigated the sources of this output variability across a motor system, from the central pattern generator (CPG) to the motor plant. In the bilaterally symmetric leech heartbeat system, the CPG orchestrates two coordinations in the bilateral hearts with different intersegmental phase relations (Δϕ) and periodic side-to-side switches. Population variability is large. We show that the system is precise within a coordination, that differences in repetitions of a coordination contribute little to population output variability, but that differences between bilaterally homologous cells may contribute to some of this variability. Nevertheless, much output variability is likely associated with genetic and life history differences among individuals. Variability of Δϕ were coordination-specific: similar at all levels in one, but significantly lower for the motor pattern than the CPG pattern in the other. Mechanisms that transform CPG output to motor neurons may limit output variability in the motor pattern.

Isoflurane Disrupts Central Pattern Generator Activity and Coordination in the Lamprey Isolated Spinal Cord

2005 ◽  
Vol 103 (3) ◽  
pp. 567-575 ◽  
Author(s):  
Steven L. Jinks ◽  
Richard J. Atherley ◽  
Carmen L. Dominguez ◽  
Karen A. Sigvardt ◽  
Joseph F. Antognini
Keyword(s):  
Spinal Cord ◽  
Central Pattern Generator ◽  
Motor Neurons ◽  
Central Pattern Generators ◽  
Volatile Anesthetics ◽  
Pattern Generator ◽  
Motor Output ◽  
Petroleum Jelly ◽  
Burst Frequency ◽  
Generator Activity

Background Although volatile anesthetics such as isoflurane can depress sensory and motor neurons in the spinal cord, movement occurring during anesthesia can be coordinated, involving multiple limbs as well as the head and trunk. However, it is unclear whether volatile anesthetics depress locomotor interneurons comprising central pattern generators or disrupt intersegmental central pattern generator coordination. Methods Lamprey spinal cords were excised during anesthesia and placed in a bath containing artificial cerebrospinal fluid and D-glutamate to induce fictive swimming. The rostral, middle, and caudal regions were bath-separated using acrylic partitions and petroleum jelly, and in each compartment, the authors recorded ventral root activity. The authors selectively delivered isoflurane (0.5, 1, and 1.5%) only to the middle segments of the spinal cord. Spectral analyses were then used to assess isoflurane effects on central pattern generator activity and coordination. Results Isoflurane dose-dependently reduced fictive locomotor activity in all three compartments, with 1.5% isoflurane nearly eliminating activity in the middle compartment and reducing spectral amplitudes in the anesthetic-free rostral and caudal compartments to 23% and 31% of baseline, respectively. Isoflurane decreased burst frequency in the caudal compartment only, to 53% of baseline. Coordination of central pattern generator activity between the rostral and caudal compartments was also dose-dependently decreased, to 42% of control at 1.5% isoflurane. Conclusion Isoflurane disrupts motor output by reducing interneuronal central pattern generator activity in the spinal cord. The effects of isoflurane on motor output outside the site of isoflurane application were presumably independent of effects on sensory or motor neurons.

Plateau potentials in motor neurons in the ventilatory system of the crab

1997 ◽  
Vol 200 (12) ◽  
pp. 1725-1736
Author(s):  
R Dicaprio
Keyword(s):  
Central Pattern Generator ◽  
Motor Neurons ◽  
Large Amplitude ◽  
Action Potentials ◽  
Experimental Tests ◽  
Pattern Generator ◽  
Plateau Potentials ◽  
Plateau Potential

The motor neurons in the crab ventilatory system have previously been considered to be passive output elements in that the generation of bursts of action potentials in these neurons during ventilation was thought to be due to cyclic inhibition and excitation from the interneurons in the ventilatory central pattern generator. This study demonstrates that the large-amplitude depolarization that underlies bursts of action potentials in ventilatory motor neurons is produced by a plateau potential. These motor neurons satisfy a number of the experimental tests that have been proposed for plateau potentials, such as triggering of the burst by a brief depolarization, termination of the burst by a hyperpolarizing input, and an all-or-none suppression of the depolarizing potential by the injection of hyperpolarizing current.

scholarly journals Feedback From Peripheral Musculature to Central Pattern Generator in the Neurogenic Heart of the Crab Callinectes sapidus: Role of Mechanosensitive Dendrites

2010 ◽  
Vol 103 (1) ◽  
pp. 83-96 ◽  
Author(s):  
Keyla García-Crescioni ◽  
Timothy J. Fort ◽  
Estee Stern ◽  
Vladimir Brezina ◽  
Mark W. Miller
Keyword(s):  
Motor Neuron ◽  
Central Pattern Generator ◽  
Motor Neurons ◽  
Callinectes Sapidus ◽  
Motor Pattern ◽  
Pattern Generator ◽  
Neuron Spike ◽  
Effector System ◽  
Spike Bursts

The neurogenic heart of decapod crustaceans is a very simple, self-contained, model central pattern generator (CPG)-effector system. The CPG, the nine-neuron cardiac ganglion (CG), is embedded in the myocardium itself; it generates bursts of spikes that are transmitted by the CG's five motor neurons to the periphery of the system, the myocardium, to produce its contractions. Considerable evidence suggests that a CPG-peripheral loop is completed by a return feedback pathway through which the contractions modify, in turn, the CG motor pattern. One likely pathway is provided by dendrites, presumably mechanosensitive, that the CG neurons project into the adjacent myocardial muscle. Here we have tested the role of this pathway in the heart of the blue crab, Callinectes sapidus . We performed “de-efferentation” experiments in which we cut the motor neuron axons to the myocardium and “de-afferentation” experiments in which we cut or ligated the dendrites. In the isolated CG, these manipulations had no effect on the CG motor pattern. When the CG remained embedded in the myocardium, however, these manipulations, interrupting either the efferent or afferent limb of the CPG-peripheral loop, decreased contraction amplitude, increased the frequency of the CG motor neuron spike bursts, and decreased the number of spikes per burst and burst duration. Finally, passive stretches of the myocardium likewise modulated the spike bursts, an effect that disappeared when the dendrites were cut. We conclude that feedback through the dendrites indeed operates in this system and suggest that it completes a loop through which the system self-regulates its activity.

scholarly journals Phase-Locked Coordination Between Two Rhythmically Active Feeding Structures in the Mollusk Clione limacina. I. Motor Neurons

2002 ◽  
Vol 87 (6) ◽  
pp. 2996-3005 ◽  
Author(s):  
Aleksey Y. Malyshev ◽  
Tigran P. Norekian
Keyword(s):  
Central Pattern Generator ◽  
Motor Neurons ◽  
Electrical Coupling ◽  
Pattern Generator ◽  
Dependent Manner ◽  
Synaptic Connections ◽  
Buccal Ganglia ◽  
Active Feeding ◽  
Clione Limacina ◽  
Specific Phase

Coordination between different motor centers is essential for the orderly production of all complex behaviors, in both vertebrates and invertebrates. The current study revealed that rhythmic activities of two feeding structures of the pteropod mollusk Clione limacina, radula and hooks, which are used to extract the prey from its shell, are highly coordinated in a phase-dependent manner. Hook protraction always coincided with radula retraction, while hook retraction coincided with radula protraction. Thus hooks and radula were always moving in the opposite phases, taking turns grabbing and pulling the prey tissue out of the shell. Identified buccal ganglia motor neurons controlling radula and hooks protraction and retraction were rhythmically active in the same phase-dependent manner. Hook protractor motor neurons were active in the same phase with radula retractor motor neurons, while hook retractor motor neurons burst in phase with radula protractor motor neurons. One of the main mechanisms underlying the phase-locked coordination was electrical coupling between hook protractor and radula retractor motor neurons. In addition, reciprocal inhibitory synaptic connections were found between hook protractor and radula protractor motor neurons. These electrical and inhibitory synaptic connections ensure that rhythmically active hooks and radula controlling motor neurons are coordinated in the specific phase-dependent manner described above. The possible existence of a single multifunctional central pattern generator for both radula and hook motor centers is discussed.

Deletions of Rhythmic Motoneuron Activity During Fictive Locomotion and Scratch Provide Clues to the Organization of the Mammalian Central Pattern Generator

2005 ◽  
Vol 94 (2) ◽  
pp. 1120-1132 ◽  
Author(s):  
Myriam Lafreniere-Roula ◽  
David A. McCrea
Keyword(s):  
Central Pattern Generator ◽  
Rhythmic Activity ◽  
Pattern Generator ◽  
Cycle Period ◽  
Fictive Locomotion ◽  
Integer Multiple ◽  
Extensor Motoneuron ◽  
Complete Failure ◽  
Motoneuron Activity ◽  
Decerebrate Cats

We examined the features of spontaneous deletions of bursts of motoneuron activity that can occur within otherwise rhythmic alternating flexor and extensor activity during fictive locomotion and scratch in adult decerebrate cats. Deletions of activity were observed both in hindlimb flexor and extensor motoneuron pools during brain stem–stimulation-evoked fictive locomotion but only in extensors during fictive scratch. Paired intracellular motoneuron recordings showed that deletions reduced the depolarization of homonymous motoneurons in qualitatively similar ways. Differences occurred in the extent to which activity in synergist motoneuron pools operating at other joints within the limb was reduced during deletions. The timing of the rhythmic activity that followed a deletion was often at an integer multiple of the preexisting locomotor or scratch cycle period. This maintenance of cycle period was also seen during deletions in which there was a complete failure of motoneuron depolarization. The activity of antagonist motoneurons was usually sustained during deletions with some rhythmic modulation at intervals of the preexisting cycle period. We discuss an organization of the central pattern generator for locomotion and scratch that functions as a single rhythm generator with separate and multiple pattern formation modules for controlling the hyper- and depolarization of subsets of motoneurons within the limb.

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