Period Differences Between Segmental Oscillators Produce Intersegmental Phase Differences in the Leech Heartbeat Timing Network

2002 ◽  
Vol 87 (3) ◽  
pp. 1603-1615 ◽  
Author(s):  
Mark A. Masino ◽  
Ronald L. Calabrese
Keyword(s):  
Central Pattern Generator ◽  
Phase Relationship ◽  
Pattern Generator ◽  
The Other ◽  
Cycle Period ◽  
Pharmacological Manipulation ◽  
The Third ◽  
The Individual ◽  
Phase Relationships ◽  
Phase Differences

Considerable experimental and theoretical effort has been exerted to understand how constant intersegmental phase relationships are produced between oscillators in segmentally organized pattern generating networks. The phase relationship between the segmental oscillators in the isolated timing network of the leech heartbeat central pattern generator is quite regular within individual preparations. However, it varies considerably among different preparations. Our goal is to determine how the phase relationships in this network are established. Here we assess whether inherent period differences, as suggested by the excitability-gradient hypothesis, play a role in establishing the phase relationships between the two coupled segmental oscillators of the leech heartbeat timing network. To do this we developed methods for reversibly uncoupling the segmental oscillators (sucrose knife) and pharmacological manipulation of the individual oscillators (split bath). Differences in inherent cycle periods between the third and fourth segmental oscillators (G3 and G4) were present in most (20 of 26) preparations. These period differences correlated with the phase differences observed between the segmental oscillators in the recoupled timing network, such that the oscillator with the faster cycle period, regardless of the segment in which it was located, led in phase in proportion to its period difference with the other oscillator. The phase differences between the original (coupled) and recoupled states of individual preparations were similar. Thus application and removal of the sucrose knife did not alter the period difference between the segmental oscillators in the timing network. Pharmacological manipulation of the uncoupled oscillators to alter the period difference between the oscillators led to similar correlated phase differences in the recoupled timing network. Across all experiments the uncoupled segmental oscillator with the faster cycle period established the cycle period of the timing network when recoupled. In conclusion, our findings indicate that an excitability-gradient plays a role in establishing the phase relationship between the segmental oscillators of the leech heartbeat central pattern generator since inherent period differences present between the oscillators are correlated to the phase relationships of the coupled/recoupled timing network.

Phase Relationships Between Segmentally Organized Oscillators in the Leech Heartbeat Pattern Generating Network

2002 ◽  
Vol 87 (3) ◽  
pp. 1572-1585 ◽  
Author(s):  
Mark A. Masino ◽  
Ronald L. Calabrese
Keyword(s):  
Spike Activity ◽  
Motor Pattern ◽  
Initiation Site ◽  
Pattern Generator ◽  
Primary Site ◽  
Secondary Site ◽  
Cycle Period ◽  
Spike Initiation ◽  
Phase Relationships ◽  
Phase Differences

Motor pattern generating networks that produce segmentally distributed motor outflow are often portrayed as a series of coupled segmental oscillators that produce a regular progression (constant phase differences) in their rhythmic activity. The leech heartbeat central pattern generator is paced by a core timing network, which consists of two coupled segmental oscillators in segmental ganglia 3 and 4. The segmental oscillators comprise paired mutually inhibitory oscillator interneurons and the processes of intersegmental coordinating interneurons. As a first step in understanding the coordination of segmental motor outflow by this pattern generator, we describe the functional synaptic interactions, and activity and phase relationships of the heart interneurons of the timing network, in isolated nerve cord preparations. In the timing network, most (∼75%) of the coordinating interneuron action potentials were generated at a primary spike initiation site located in ganglion 4 (G4). A secondary spike initiation site in ganglion 3 (G3) became active in the absence of activity at the primary site. Generally, the secondary site was characterized by a reluctance to burst and a lower spike frequency, when compared with the primary site. Oscillator interneurons in G3 inhibited spike activity at both initiation sites, whereas oscillator interneurons in G4 inhibited spike activity only at the primary initiation site. This asymmetry in the control of spike activity in the coordinating interneurons may account for the observation that the phase of the coordinating interneurons is more tightly linked to the G3 than G4 oscillator interneurons. The cycle period of the timing network and the phase difference between the ipsilateral G3 and G4 oscillator interneurons were regular within individual preparations, but varied among preparations. This variation in phase differences observed across preparations implies that modulated intrinsic membrane and synaptic properties, rather than the pattern of synaptic connections, are instrumental in determining phase within the timing network.

scholarly journals Maintenance of motor pattern phase relationships in the ventilatory system of the crab

1997 ◽  
Vol 200 (6) ◽  
pp. 963-974
Author(s):  
R Dicaprio ◽  
G Jordan ◽  
T Hampton
Keyword(s):  
Membrane Potential ◽  
Central Pattern Generator ◽  
Motor Pattern ◽  
Pattern Generator ◽  
Rate Of Change ◽  
Cycle Period ◽  
Potential Oscillation ◽  
Cycle Frequency ◽  
Membrane Potential Oscillation ◽  
Phase Relationships

The central pattern generator responsible for the gill ventilation rhythm in the shore crab Carcinus maenas can produce a functional motor pattern over a large (eightfold) range of cycle frequencies. One way to continue to generate a functional motor pattern over such a large frequency range would be to maintain the relative timing (phase) of the motor pattern as cycle frequency changes. This hypothesis was tested by measuring the phase of eight events in the motor pattern from extracellular recordings at different rhythm frequencies. The motor pattern was found to maintain relatively constant phase relationships among the various motor bursts in this rhythm over a large (sevenfold) range of cycle frequencies, although two phase-maintaining subgroups could be distinguished. Underlying this phase maintenance is a corresponding change in the time delay between events in the motor pattern ranging from 470 to 1800 ms over a sevenfold (300­2100 ms) change in cycle period. Intracellular recordings from ventilatory neurons indicate that there is very little change in the membrane potential oscillation in the motor neurons with changes in cycle frequency. However, recordings from nonspiking interneurons in the ventilatory central pattern generator reveal that the rate of change of the membrane potential oscillation of these neurons varies in proportion to changes in cycle frequency. The strict biomechanical requirements for efficient pumping by the gill bailer, and the fact that work is performed in all phases of the motor pattern, may require that this motor pattern maintain phase at all rhythm frequencies.

Hawthorne on Romantic Love and the Status of Women

PMLA ◽  
1954 ◽  
Vol 69 (1) ◽  
pp. 89-98
Author(s):  
Morton Cronin
Keyword(s):  
Romantic Love ◽  
The Other ◽  
The Third ◽  
The World ◽  
The Status ◽  
The Individual ◽  
Hester Prynne ◽  
Status Of Women

The women that Hawthorne created divide rather neatly into three groups. Such fragile creatures as Alice Pyncheon and Priscilla, who are easily dominated by other personalities, form one of these groups. Another is made up of bright, self-reliant, and wholesome girls, such as Ellen Langton, Phoebe, and Hilda. The third consists of women whose beauty, intellect, and strength of will raise them to heroic proportions and make them fit subjects for tragedy. Hester Prynne, Zenobia, and Miriam—these women are capable of tilting with the world and risking their souls on the outcome. With them in particular Hawthorne raises and answers the question of the proper status of women in society and the relation, whether subordinate or superior, that love should bear to the other demands that life makes upon the individual. With the other types Hawthorne fills out his response to that question.

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.

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.

EFFECT OF AMPICILLIN ADMINISTRATION ON THE EXCRETION OF TWELVE OESTROGENS IN PREGNANCY URINE

1975 ◽  
Vol 80 (3) ◽  
pp. 551-557 ◽  
Author(s):  
H. Adlercreutz ◽  
F. Martin ◽  
M. J. Tikkanen ◽  
M. Pulkkinen
Keyword(s):  
Enterohepatic Circulation ◽  
Basic Mechanism ◽  
The Other ◽  
Control Value ◽  
The Third ◽  
Urinary Levels ◽  
Pregnancy Urine ◽  
The Mean ◽  
The Individual ◽  
In Pregnancy

ABSTRACT The excretion of twelve oestrogens in urine, pooled daily from a group of pregnant women, was determined before, during and after ampicillin administration (2 g/day, for 3 days). On the second day of ampicillin administration total oestrogen excretion fell to 67 % of the mean control value, oestriol excretion to 69% and that of the other eleven individual oestrogens to an average of 62 % of the mean control values. In general, on the third day of treatment and on the two post-treatment days this decrease tended to be corrected. The patterns of change in the urinary levels of the individual metabolites provided no clear lead to the basic mechanism of ampicillin impairment of oestrogen excretion. However, as the drug affected all their excretion in more or less the same way as it did that of oestriol, it is possible that ampicillin interferes primarily with their enterohepatic circulation in the mother as has been established with reasonable certainty in the case of oestriol.

scholarly journals The discovery of third pole between a pair of like poles of an iron-core solenoid and a permanent magnet

2019 ◽  
Author(s):  
Umer Farooq
Keyword(s):  
Permanent Magnet ◽  
The Other ◽  
Iron Core ◽  
Magnetic Pole ◽  
Simple Experiment ◽  
The Third ◽  
The Individual ◽  
Experimental Findings ◽  
Vector Sum ◽  
Repulsion And Attraction

Creation of a third magnetic pole between a pair of like poles has been detected. Reason of the creation of the third pole is very simple but effects and ultimate results of the third pole are unbelievably immense. The result of a simple experiment is the basis of this discovery. In the experiment, like poles of an iron core-solenoid and a permanent magnet have been interacted with each other. Unexpectedly, both repulsion and attraction were produced between the like poles (one after the other) instead of only repulsion.Not only scientists have never conducted this experiment but also their assumption about this matter is totally contrary to the experimental findings. Opinion of a qualified scientist about this matter: “The strength and direction of a magnetic field at any point is the vector sum of all the individual fields at that point, so the situation you describe is not possible as the field at any point will always be a single vector. So it is not possible for the unaligned domains to be attracted by the permanent magnet while other domains are repelled because the unaligned domains will be acted upon only by the net field.” There seems an irremovable contradiction between the experimental findings and the opinion of the scientist but the discovery of the third magnetic pole solves this problem sufficiently.

Further Clinical Observations in Cases of Acute Mania, particularly Adolescent Mania

1903 ◽  
Vol 49 (206) ◽  
pp. 441-447 ◽  
Author(s):  
Lewis C. Bruce
Keyword(s):  
The Other ◽  
Acute Mania ◽  
Polymorphonuclear Leucocytes ◽  
The Third ◽  
Clinical Observations ◽  
Control Serum ◽  
The Individual

Following up my observations made upon the blood of patients suffering from acute continuous mania read before this Association at the autumn meeting, I have been able to observe three cases of acute continuous mania in adults which relapsed while in the asylum. The results of the first series of observations were that in every case of acute continuous mania there existed a leucocytosis which persisted after recovery indefinitely. I advanced the theory that this leucocytosis was a protective leucocytosis. In the three patients who relapsed the leucocytosis was found to have fallen to below 13,000 per c.mm. of blood, instead of being nearer 20,000 per c.mm. of blood, which is characteristic of the recovered cases of mania. The polymorphonuclear leucocytes averaged 60 per cent, in two of these patients, and 47 per cent, in the third. In one of these patients the attack passed off in two days, and the leucocytosis at once rose to 25,000 per c.mm. of blood. The other two patients passed into a definite second attack, and their leucocytes averaged 15,000 to 16,000 per c.mm. of blood, with a polymorphonuclear percentage of 60 or below 60. The fact that the leucocytosis fell in each patient at the commencement of the attack, and rose at once in the patient who recovered from the relapse, strengthens the hypothesis that acute continuous mania is an infective disorder, and that immunity from maniacal attacks rests upon the resistive power of the individual patient. This hypothesis receives further support from the fact that there exists in the blood of patients suffering from acute mania a specific agglutinin. During the month of November a patient suffering from acute mania was admitted to Murthly. The patient was so ill that I did not think she would live many days. I isolated from the blood a very small coccus, which was a pure growth, but, as the patient was exhausted, I regarded the organism as a terminal infection. The patient improved, however, and three weeks later I tested the agglutinative power of her serum upon this organism in a dilution of 1 in 30. Agglutination was complete in three hours, while the serum of a member of the staff in a dilution of 1 in 20 produced no action in twenty hours. Since then I have made fifty agglutination tests with this organism. Only ten of these cases, however, have been pure cases of continuous mania. Eight gave a decided definite agglutination, one was doubtful, and the tenth—one of the patients above noted, who relapsed—gave no reaction. No “control” serum ever gave a reaction, nor did the serum of these patients suffering from mania agglutinate other organisms. The agglutinin in the blood was therefore a specific agglutinin.

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.

Sign in / Sign up

Export Citation Format

Share Document