Coupling of Efferent Neuromodulatory Neurons to Rhythmical Leg Motor Activity in the Locust

1998 ◽  
Vol 79 (1) ◽  
pp. 361-370 ◽  
Author(s):  
Sylvie Baudoux ◽  
Carsten Duch ◽  
Oliver T. Morris
Keyword(s):  
Motor Activity ◽  
Motor Neurons ◽  
Spike Activity ◽  
Motor Pattern ◽  
Rhythmic Activity ◽  
Motor Output ◽  
Variable Activity ◽  
Metathoracic Ganglion ◽  
Dum Neurons ◽  
Dorsal Unpaired Median

Baudoux, Sylvie, Carsten Duch, and Oliver T. Morris. Coupling of efferent neuromodulatory neurons to rhythmical leg motor activity in the locust. J. Neurophysiol. 79: 361–370, 1998. The spike activity of neuromodulatory dorsal unpaired median (DUM) neurons was analyzed during a pilocarpine-induced motor pattern in the locust. Paired intracellular recordings were made from these octopaminergic neurons during rhythmic activity in hindleg motor neurons evoked by applying pilocarpine to an isolated metathoracic ganglion. This motor pattern is characterized by two alternating phases: a levator phase, during which levator, flexor, and common inhibitor motor neurons spike, and a depressor phase, during which depressor and extensor motor neurons spike. Three different subpopulations of efferent DUM neurons could be distinguished during this rhythmical motor pattern according to their characteristic spike output. DUM 1 neurons, which in the intact animal do not innervate muscles involved in leg movements, showed no change apart from a general increase in spike frequency. DUM 3 and DUM 3,4 neurons produced the most variable activity but received frequent and sometimes pronounced hyperpolarizations that were often common to both recorded neurons. DUM 5 and DUM 3,4,5 neurons innervate muscles of the hindleg and showed rhythmical excitation leading to bursts of spikes during rhythmic activity of the motor neurons, which innervate these same muscles. Sometimes the motor output was coordinated across both sides of the ganglion so that there was alternating activity between levators of both sides. In these cases, the spikes of DUM 5 and DUM 3,4,5 neurons and the hyperpolarization of DUM 3 and DUM 3,4 neurons occurred at particular phases in the motor pattern. Our data demonstrate a central coupling of specific types of DUM neurons to a rhythmical motor pattern. Changes in the spike output of these particular efferent DUM neurons parallel changes in the motor output. The spike activity of DUM neurons thus may be controlled by the same circuits that determine the action of the motor neurons. Functional implications for real walking are discussed.

Action of locust neuromodulatory neurons is coupled to specific motor patterns

1995 ◽  
Vol 74 (1) ◽  
pp. 347-357 ◽  
Author(s):  
M. Burrows ◽  
H. J. Pfluger
Keyword(s):  
Motor Neurons ◽  
Motor Pattern ◽  
Intracellular Recordings ◽  
Flexor Muscle ◽  
Motor Patterns ◽  
Specific Subset ◽  
Metathoracic Ganglion ◽  
Flexor Muscles ◽  
Dum Neurons ◽  
Dorsal Unpaired Median

1. Many muscles of the locust are supplied by dorsal unpaired median neurons (DUM neurons) that release octopamine and alter the contractions caused by spikes in motor neurons. To determine when these neuromodulatory neurons are normally activated during behaviour, intracellular recordings were made simultaneously from them and from identified motor neurons during the specific motor pattern that underlies kicking. A kick consists of a rapid and powerful extension of the tibia of one or both hind legs that is produced by a defined motor pattern. Only 3 identified DUM neurons of the 20 in the metathoracic ganglion spike during a kick, and they supply muscles involved in generating the kick. Their spikes occur in a distinctive and repeatable pattern that is closely linked to the pattern of spikes in the flexor and extensor tibiae motor neurons. When the extensor and flexor muscles cocontract, these three DUM neurons produce a burst of spikes at frequencies that can rise to 25 Hz, and with the number of spikes (3-15) related to the duration of this phase of the motor pattern. The spikes stop when the flexor muscle is inhibited and therefore before the tibia is extended rapidly. The other DUM neurons which supply muscles that are not directly involved in kicking are either inhibited or spike only sporadically. 2. The activation of a specific subset of DUM neurons during kicking may thus be timed to influence the action of the muscles that participate in this movement and appear to be controlled by the same circuits that determine the actions of the participating motor neurons. These modulatory neurons thus have specific individual actions in the control of movement.

Analysis and modeling of the multisegmental coordination of shortening behavior in the medicinal leech. I. Motor output pattern

1992 ◽  
Vol 68 (5) ◽  
pp. 1683-1692 ◽  
Author(s):  
G. Wittenberg ◽  
W. B. Kristan
Keyword(s):  
Motor Neurons ◽  
Longitudinal Muscle ◽  
Motor Pattern ◽  
Mechanical Stimulus ◽  
Medicinal Leech ◽  
Motor Output ◽  
Simultaneous Excitation ◽  
Ventral Longitudinal Muscle ◽  
Output Pattern ◽  
Simple Behavior

1. To understand how a multisegmental animal coordinates motor activity over more than one segment, we studied shortening behavior in the medicinal leech, in which several segments contract longitudinally in response to a moderately strong mechanical stimulus. 2. We first demonstrated that the neuronal activity responsible for shortening behavior occurred in semi-intact and isolated nerve cord preparations, and then characterized the responses of motor neurons in isolated preparations. The motor output during shortening was simultaneous excitation of motor neurons innervating dorsal longitudinal muscle and of motor neurons innervating ventral longitudinal muscle. 3. The stronger the stimulus, the more segments produced the shortening motor output, with the segments nearest the stimulus recruited first. 4. Although the shortening response was produced in several segments near the site of stimulation, it was never produced in the stimulated segment, where the local bending motor output pattern was produced. The motor pattern suggests that shortening, initially considered a very simple behavior, requires the involvement of at least few segmentally iterated interneurons.

Rhythmic patterns evoked in locust leg motor neurons by the muscarinic agonist pilocarpine

1993 ◽  
Vol 69 (5) ◽  
pp. 1583-1595 ◽  
Author(s):  
S. Ryckebusch ◽  
G. Laurent
Keyword(s):  
Motor Neurons ◽  
Rhythmic Activity ◽  
Cycle Period ◽  
Muscarinic Agonist ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Metathoracic Ganglion ◽  
Common Drive ◽  
Muscarinic Cholinergic

1. When an isolated metathoracic ganglion of the locust was superfused with the muscarinic cholinergic agonist pilocarpine, rhythmic activity was induced in leg motor neurons. The frequency of this induced rhythm increased approximately linearly from 0 to 0.2 Hz with concentrations of pilocarpine from 10(-5) to 10(-4) M. Rhythmic activity evoked by pilocarpine could be completely and reversibly blocked by 3 x 10(-5) M atropine, but was unaffected by 10(-4) M d-tubocurarine. 2. For each hemiganglion, the observed rhythm was characterized by two main phases: a levator phase, during which the anterior coxal rotator, levators of the trochanter, flexors of the tibia, and common inhibitory motor neurons were active; and a depressor phase, during which depressors of the trochanter, extensors of the tibia, and depressors of the tarsus were active. Activity in depressors of the trochanter followed the activity of the levators of the trochanter with a short, constant interburst latency. Activity in the levator of the tarsus spanned both phases. 3. The levator phase was short compared with the period (0.5-2 s, or 10-20% of the period) and did not depend on the period. The interval between the end of a levator burst and the beginning of the following one thus increased with cycle period. The depressor phase was more variable, and was usually shorter than the interval between successive levator bursts. 4. Motor neurons in a same pool often received common discrete synaptic potentials (e.g., levators of trochanter or extensors of tibia), suggesting common drive during the rhythm. Coactive motor neurons on opposite sides (such as left trochanteral depressors and right trochanteral levators), however, did not share obvious common postsynaptic potentials. Depolarization of a pool of motor neurons during its phase of activity was generally accompanied by hyperpolarization of its antagonist(s) on the same side. 5. Rhythmic activity was generally evoked in both hemiganglia of the metathoracic ganglion, but the intrinsic frequencies of the rhythms on the left and right were usually different. The activity of the levators of the trochanter on one side, however, was strongly coupled to that of the depressors of the trochanter on the other side. 6. The locomotory rhythm was weakly coupled to the ventilatory rhythm such that trochanteral levator activity on either side never occurred during the phase of spiracle opener activity corresponding to inspiration. 7. The rhythmic activity observed in vitro bears many similarities to patterns of neural and myographic activity recorded during walking. The similarities and differences are discussed.

scholarly journals Behaviour and Motor Output for an Insect Walking on a Slippery Surface: II. Backward Walking

1985 ◽  
Vol 118 (1) ◽  
pp. 287-296 ◽  
Author(s):  
D. GRAHAM ◽  
S. EPSTEIN
Keyword(s):  
Motor Activity ◽  
Motor Pattern ◽  
Motor Output ◽  
Retractor Muscle ◽  
Backward Walking ◽  
Stick Insects ◽  
Weak Activity ◽  
Slippery Surface ◽  
Walking Recovery ◽  
Simple Phase

Coordination of the legs and the motor activity of four muscles in a middle leg were recorded in adult stick insects walking on a slippery glass surface. Backward walking was not achieved by a simple phase shift of levators and depressors. In all muscles examined, there was a considerable disturbance of motor activity during backward walking when compared with that found in forward walking. In backward walking, recovery was performed, in the middle leg, by strong fast unit activity in the retractor muscle and all muscles showed weak activity at inappropriate times. Fast motor output appeared to be superimposed on the forward walking motor pattern to produce the movements required for backward walking in this insect.

Crawling motor patterns induced by pilocarpine in isolated larval nerve cords of Manduca sexta

1996 ◽  
Vol 76 (5) ◽  
pp. 3178-3195 ◽  
Author(s):  
R. M. Johnston ◽  
R. B. Levine
Keyword(s):  
Motor Activity ◽  
Motor Neurons ◽  
Nerve Cord ◽  
Body Wall ◽  
Motor Nerve ◽  
Rhythmic Activity ◽  
Cycle Period ◽  
Nerve Activity ◽  
Bursting Activity ◽  
Nerve Cords

1. Larval crawling is a bilaterally symmetrical behavior that involves an anterior moving wave of motor activity in the body wall muscles in conjunction with sequential movements of the abdominal prolegs and thoracic legs. The purpose of this study was to determine whether the larval CNS by itself and without phasic sensory feedback was capable of producing patterned activity associated with crawling. To establish the extent of similarity between the output of the isolated nerve cord and crawling, the motor activity produced in isolated larval nerve cords was compared with the motor activity from freely crawling larvae. 2. When exposed to the muscarinic receptor agonist pilocarpine (1.0 mM), isolated larval nerve cords produced long-lasting rhythmic activity in the motor neurons that supply the thoracic leg, abdominal body wall, and abdominal proleg muscles. The rhythmic activity evoked by pilocarpine was abolished reversibly and completely by bath application of the muscarinic-receptor antagonist atropine (0.01 mM) in conjunction with pilocarpine (1.0 mM), suggesting that the response was mediated by muscarinic-like acetylcholine receptors. 3. Similar to crawling in intact animals, the evoked activity in isolated nerve cords involved bilaterally symmetrical motor activity that progressed from the most posterior abdominal segment to the most anterior thoracic segment. The rhythmic activity in thoracic leg, abdominal proleg, and abdominal body wall motor neurons showed intrasegmental and intersegmental cycle-to-cycle coupling. The average cycle period for rhythmic activity in the isolated nerve cord was approximately 2.5 times slower than the cycle period for crawling in intact larvae, but not more variable. 4. Like crawling in intact animals, in isolated nerve cords, bursting activity in the dorsal body wall motor neurons occurred before activity in ventral/lateral body wall motor neurons within an abdominal segment. The evoked bursting activity recorded from the proleg nerve was superimposed on a high level of tonic activity. 5. In isolated nerve cords, bursts of activity in the thoracic leg levator/extensor motor neurons alternated with bursts of activity in the depressor/flexor motor neurons. The burst duration of the levator/extensor activity was brief and remained relatively steady as cycle period increased. The burst duration of the depressor/ flexor activity occupied the majority of an average cycle and increased as cycle period increased. The phase of both levator/extensor motor nerve activity and depressor/flexor motor nerve activity remained relatively stable over the entire range of cycle periods. The timing and patterning of thoracic leg motor neuron activity in isolated nerve cords quantitatively resembled thoracic leg motor activity in freely crawling larvae. 6. The rhythmic motor activity generated by an isolated larval nerve cord resembled a slower version of normal crawling in intact larvae. Because of the many similarities between activity induced in the isolated nerve cord and the muscle activity and movements of thoracic and abdominal segments during crawling, we concluded that central mechanisms can establish the timing and patterning of the crawling motor pattern and that crawling may reflect the output of a central pattern generating network.

scholarly journals Induction of a non-rhythmic motor pattern by nitric oxide in hatchling Rana temporaria embryos

2001 ◽  
Vol 204 (7) ◽  
pp. 1307-1317 ◽  
Author(s):  
D.L. McLean ◽  
J.R. McDearmid ◽  
K.T. Sillar
Keyword(s):  
Nitric Oxide ◽  
Motor Activity ◽  
Motor Neurons ◽  
Rana Temporaria ◽  
Motor Pattern ◽  
Ventral Root ◽  
The Body ◽  
Resting Potential ◽  
No Donors ◽  
Rhythmic Motor

Nitric oxide (NO) is a ubiquitous neuromodulator with a diverse array of functions in a variety of brain regions, but a role for NO in the generation of locomotor activity has yet to be demonstrated. The possibility that NO is involved in the generation of motor activity in embryos of the frog Rana temporaria was investigated using the NO donors S-nitroso-n-acetylpenicillamine (SNAP; 100--500 micromol l(−1)) and diethylamine nitric oxide complex sodium (DEANO; 25--100 micromol l(−1)). Immobilised Rana temporaria embryos generate a non-rhythmic ‘lashing’ motor pattern either spontaneously or in response to dimming of the experimental bath illumination. Bath-applied NO donors triggered a qualitatively similar motor pattern in which non-rhythmic motor bursts were generated contra- and ipsilaterally down the length of the body. The inactive precursor of SNAP, n-acetyl-penicillamine (NAP), at equivalent concentrations did not trigger motor activity. NO donors failed to initiate swimming and had no measurable effects on the parameters of swimming induced by electrical stimulation. Intracellular recordings with potassium-acetate-filled electrodes revealed that the bursts of ventral root discharge induced by NO donors were accompanied by phasic depolarisations in motor neurons. During the inter-burst intervals, periods of substantial membrane hyperpolarization below the normal resting potential were observed, presumably coincident with contralateral ventral root activity. With KCl-filled electrodes, inhibitory potentials were strongly depolarising, suggesting that inhibition was Cl(−)-dependent. The synaptic drive seen in motor neurons after dimming of the illumination was very similar to that induced by the NO donors. NADPH-diaphorase histochemistry identified putative endogenous sources of NO in the central nervous system and the skin. Three populations of bilaterally symmetrical neurons were identified within the brainstem. Some of these neurons had contralateral projections and many had axonal processes that projected to and entered the marginal zones of the spinal cord, suggesting that they were reticulospinal.

Heartbeat Control in Leeches. II. Fictive Motor Pattern

2004 ◽  
Vol 91 (1) ◽  
pp. 397-409 ◽  
Author(s):  
Angela Wenning ◽  
Andrew A. V. Hill ◽  
Ronald L. Calabrese
Keyword(s):  
Motor Neurons ◽  
Sensory Feedback ◽  
Coordination Mode ◽  
Motor Pattern ◽  
Preceding Paper ◽  
Rhythmic Activity ◽  
Pattern Generator ◽  
Inhibitory Input ◽  
Combine Data ◽  
Coordination Modes

The rhythmic beating of the tube-like hearts in the medicinal leech is driven and coordinated by rhythmic activity in segmental heart motor neurons. The motor neurons are controlled by rhythmic inhibitory input from a network of heart interneurons that compose the heartbeat central pattern generator. In the preceding paper, we described the constriction pattern of the hearts in quiescent intact animals and showed that one heart constricts in a rear-to-front wave (peristaltic coordination mode), while the other heart constricts in near unison over its length (synchronous coordination mode) and that they regularly switch coordination modes. Here we analyze intersegmental and side-to-side-coordination of the fictive motor pattern for heartbeat in denervated nerve cords. We show that the intersegmental phase relations among heart motor neurons in both coordination modes are independent of heartbeat period. This finding enables us to combine data from different experiments to form a detailed analysis of the relative phases, duty cycle, and intraburst spike frequency of the bursts of the segmental heart motor neurons. The fictive motor pattern and the constriction pattern seen in intact leeches closely match in their intersegmental and side-to-side coordination, indicating that sensory feedback is not necessary for properly phased intersegmental coordination. Moreover, the regular switches in coordination mode of the fictive motor pattern mimic those seen in intact animals indicating that these switches likely arise by a central mechanism.

Plasticity in the multifunctional buccal central pattern generator of Helisoma illuminated by the identification of phase 3 interneurons

1996 ◽  
Vol 75 (2) ◽  
pp. 561-574 ◽  
Author(s):  
E. M. Quinlan ◽  
A. D. Murphy
Keyword(s):  
Motor Activity ◽  
Motor Neuron ◽  
Central Pattern Generator ◽  
Motor Neurons ◽  
Motor Pattern ◽  
Pattern Generator ◽  
Neuron Activity ◽  
Phase 2 ◽  
Phase 3 ◽  
Standard Pattern

1. The mechanism for generating diverse patterns of buccal motor neuron activity was explored in the multifunctional central pattern generator (CPG) of Helisoma. The standard pattern of motor neuron activity, which results in typical feeding behavior, consists of three distinct phases of buccal motor neuron activity. We have previously identified CPG interneurons that control the motor neuron activity during phases 1 and 2 of the standard pattern. Here we identify a pair of interneurons responsible for buccal motor neuron activity during phase 3, and examine the variability in the interactions between this third subunit and other subunits of the CPG. 2. During the production of the standard pattern, phase 3 excitation in many buccal motor neurons follows a prominent phase 2 inhibitory postsynaptic potential. Therefore phase 3 excitation was previously attributed to postinhibitory rebound (PIR) in these motor neurons. Two classes of observations indicated that PIR was insufficient to account for phase 3 activity, necessitating phase 3 interneurons. 1) A subset of identified buccal neurons is inhibited during phase 3 by discrete synaptic input. 2) Other identified buccal neurons display discrete excitation during both phases 2 and 3. 3. A bilaterally symmetrical pair of CPG interneurons, named N3a, was identified and characterized as the source of phase 3 postsynaptic potentials in motor neurons. During phase 3 of the standard motor pattern, interneuron N3a generated bursts of action potentials. Stimulation of N3a, in quiescent preparations, evoked a depolarization in motor neurons that are excited during phase 3 and a hyperpolarization in motor neurons that are inhibited during phase 3. Hyperpolarization of N3a during patterned motor activity eliminated both phase 3 excitation and inhibition. Physiological and morphological characterization of interneuron N3a is provided to invite comparisons with possible homologues in other gastropod feeding CPGs. 4. These data support a model proposed for the organization of the tripartite buccal CPG. According to the model, each of the three phases of buccal motor neuron activity is controlled by discrete subsets of pattern-generating interneurons called subunit 1 (S1), subunit 2 (S2), and subunit 3 (S3). The standard pattern of buccal motor neuron activity underlying feeding is mediated by an S1-S2-S3 sequence of CPG subunit activity. However, a number of "nonstandard" patterns of buccal motor activity were observed. In particular, S2 and S3 activity can occur independently or be linked sequentially in rhythmic patterns other than the standard feeding pattern. Simultaneous recordings of S3 interneuron N3a with effector neurons indicated that N3a can account for phase-3-like postsynaptic potentials (PSPs) in nonstandard patterns. The variety of patterns of buccal motor neuron activity indicates that each CPG subunit can be active in the absence of, or in concert with, activity in any other subunit. 5. To explore how CPG activity may be regulated to generate a particular motor pattern from the CPG's full repertoire, we applied the neuromodulator serotonin. Serotonin initiated and sustained the production of an S2-S3 pattern of activity, in part by enhancing PIR in S3 interneuron N3a after the termination of phase 2 inhibition.

Central input to primary afferent neurons in crayfish, Pacifastacus leniusculus, is correlated with rhythmic motor output of thoracic ganglia

1986 ◽  
Vol 55 (4) ◽  
pp. 678-688 ◽  
Author(s):  
K. T. Sillar ◽  
P. Skorupski
Keyword(s):  
Motor Neurons ◽  
Motor Pattern ◽  
Reversal Potential ◽  
Motor Output ◽  
Resting Membrane Potential ◽  
Strongly Correlated ◽  
Motor Patterns ◽  
Thoracic Ganglia ◽  
Rhythmic Motor ◽  
Receptor Organ

A preparation is described in which the thoracic ganglia of the crayfish are isolated together with the thoracocoxal muscle receptor organ (TCMRO) of the fourth leg. This preparation allows intracellular analysis of both centrally generated and reflex activity in leg motor neurons (MNs). The isolated thoracic ganglia can spontaneously generate a rhythmic motor pattern resembling that used during forward walking (Fig. 4). This involves the reciprocal activity of promotor and remotor MNs, with levator MNs firing in phase with promotor bursts. Stretch of the TCMRO in quiescent preparations evokes a resistance reflex in promotor MNs (Fig. 6). In more active preparations the response is variable and often becomes an assistance reflex, with excitation of remotor MNs on stretch (Fig. 7). When rhythmic motor patterns occur, the neuropilar processes of the S and T fibers receive central inputs that are strongly correlated with the oscillatory drive to the MNs and probably have the same origin (Figs. 8 and 9). Central inputs to the S and T fibers occur in opposite phases within a cycle of rhythmic motor output. The S fiber is depolarized in phase with promotor MNs and the T fiber in phase with remotor activity. The input to the T fiber is shown to be a chemical synaptic drive that has a reversal potential approximately 14 mV more depolarized than the fiber's resting membrane potential. This input substantially modulates the amplitude and waveform of passively propagated receptor potentials generated by TCMRO stretch (Fig. 11). It is argued that the central inputs to the TCMRO afferents will modulate proprioceptive feedback resulting from voluntary movements.

Analysis and modeling of the multisegmental coordination of shortening behavior in the medicinal leech. II. Role of identified interneurons

1992 ◽  
Vol 68 (5) ◽  
pp. 1693-1707 ◽  
Author(s):  
G. Wittenberg ◽  
W. B. Kristan
Keyword(s):  
Nervous System ◽  
Motor Neurons ◽  
Motor Pattern ◽  
Back Propagation ◽  
Motor Output ◽  
Sensory Cells ◽  
Motor Patterns ◽  
Trained Neural Network ◽  
Motor Effects

1. Mechanical stimulation of the leech, Hirudo medicinalis, elicits withdrawal behavior that has two components: local bending in the segment stimulated and shortening in outlying segments. Local bending is characterized by excitation of longitudinal muscle on one side of the segment and inhibition on the other side. In shortening, all longitudinal muscles are excited. We wished to understand how these distinct motor patterns are produced by a nervous system with segmentally iterated neurons, a configuration that places some limitations on the complexity of connection patterns. 2. We searched for neurons in the segmental nervous system that subserved shortening behavior, expecting to find at least one interneuron in each segment that was involved in shortening behavior exclusively. We found instead that all interneurons involved in shortening are also involved in local bending, and no individual interneuron can completely account for shortening. 3. The motor output caused by individual identified interneurons is not entirely consistent with the shortening motor output pattern. For instance, one interneuron, cell 115, has the same pattern of motor effects from segment to segment, causing excitation of dorsal excitatory motor neurons and inhibition of ventral excitatory motor neurons. These effects would cause dorsal local bending, not shortening, in a few segments. Only one interneuron, cell 125, has motor effects that would cause shortening. 4. Individual interneurons were hyperpolarized while single sensory cells were stimulated, to quantify the contributions of individual interneurons to the observed motor pattern. Interneurons 115 and 125, and the inhibitory motor neuron, cell 1, were found to have significant roles in producing the shortening motor output. 5. A quantitative estimate of the role of each interneuron type showed that the identified interneurons account for most of the excitation of dorsal motor neurons, but for very little of the excitation of ventral motor neurons. This predicts that at least one additional interneuron type remains to be identified, one that would provide excitation to ventral motor neurons in several segments. 6. A back-propagation trained neural network model was constructed to predict the connections of the as yet unidentified interneurons. To match the known properties of interneurons, it was necessary to include a segmental similarity constraint in the training algorithm for segmentally iterated model neurons. The modeled networks predicted that there are at least two kinds of interneurons yet to be found. Also, the modeling showed that interneurons can have input and output patterns that differ very little from segment to segment but yet produce major differences in the motor output.

Sign in / Sign up

Export Citation Format

Share Document