Behavioral Function of Glutamatergic Interneurons in the Feeding System of Lymnaea: Plateauing Properties and Synaptic Connections with Motor Neurons

1997 ◽  
Vol 78 (6) ◽  
pp. 3386-3395 ◽  
Author(s):  
Matthew J. Brierley ◽  
Kevin Staras ◽  
Paul R. Benjamin
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Neuron Activity ◽  
Synaptic Connections ◽  
Feeding System ◽  
Behavioral Function ◽  
Buccal Ganglion ◽  
Feeding Cycle ◽  
Symmetrical Pair ◽  
Main Component

Brierley, Matthew J., Kevin Staras, and Paul R. Benjamin. Behavioral function of glutamatergic interneurons in the feeding system of Lymnaea: plateauing properties and synaptic connections with motor neurons. J. Neurophysiol. 78: 3386–3395, 1997. Intracellular recording techniques were used to examine the electrical properties and behavioral function of a novel type of retraction phase interneuron, the N2 ventral (N2v) cells in the feeding network of the snail Lymnaea. The N2vs were compared with the previously identified N2 cells that now are renamed the N2 dorsal (N2d) cells. The N2vs are a bilaterally symmetrical pair of electrotonically coupled plateauing interneurons that are located on the ventral surfaces of the buccal ganglia. Their main axons project to the opposite buccal ganglion, but they have an additional fine process in the postbuccal nerve. N2v plateaus that outlast the duration of the stimulus can be triggered by depolarizing current pulses and prematurely terminated by applied hyperpolarizing pulses. Gradually increasing the amplitude of depolarizing pulses reveals a clear threshold for plateau initiation. N2v plateauing persists in a high Mg2+/nominally zero Ca2+ saline that blocks chemical synaptic connections, suggesting an endogenous mechanism for plateau generation. The N2vs fire sustained bursts of action potentials throughout the N2/rasp phase of the fictive feeding cycle and control the retraction phase feeding motor neurons. The N2vs excite the B3 and B9 feeding motor neurons to fire during the rasp phase of the feeding cycle. They also inhibit the B7 and B8 feeding motor neurons. The B8 cells recover from inhibition and fire during the following swallowing phase. These synaptic connections appear to be monosynaptic as they persist in high Mg2+/high Ca2+ (HiDi) saline that blocks polysynaptic pathways. Strong current-induced plateaus in the N2vs generate brief inhibitory postsynaptic responses in the B4CL rasp phase motor neurons, but this was due to the indirect N2v → N2d → B4CL pathway. The N2vs are coupled electrotonically to the N2d cells, and triggering plateau in a N2v usually induced one or two spikes in a N2d. Previous experiments showed that the N2ds generate plateau potentials during a fictive feeding cycle. Here we show that the main component of the “plateauing” waveform is due to the electrotonic coupling with the N2v cells. The differential synaptic connections of the N2v and N2d cells with retraction phase motor neurons results in a sequence of motor neuron burst activity B9 → B4CL → B8 that produces the full retraction (rasp → swallow) movements of the feeding apparatus (buccal mass). We conclude that the N2v cells are an essential component of the interneuronal network required to produce feeding motor neuron activity.

Aplysia ink release: central locus for selective sensitivity to long-duration stimuli

1979 ◽  
Vol 42 (5) ◽  
pp. 1223-1232 ◽  
Author(s):  
E. Shapiro ◽  
J. Koester ◽  
J. H. Byrne
Keyword(s):  
Motor Neuron ◽  
Spike Train ◽  
Motor Neurons ◽  
Neural Circuit ◽  
Reversal Potential ◽  
Secretory Process ◽  
Neuron Activity ◽  
Long Duration ◽  
Noxious Stimuli ◽  
Selective Sensitivity

1. A behavioral and electrophysiological analysis of defensive ink release in Aplysia californica was performed to examine the response of this behavior and its underlying neural circuit to various-duration noxious stimuli. 2. Three separate behavioral protocols were employed using electrical shocks to the head as noxious stimuli to elicit ink release. Ink release was found to be selectively responsive to longer duration stimuli, and to increase in a steeply graded fashion as duration is increased. 3. Intracellular stimulation of ink motor neurons revealed that ink release is a linear function of motor neuron spike train duration, indicating that the selective sensitivity of the behavior to long-duration stimuli is not due to a nonlinearity in the glandular secretory process. 4. In contrast, electrophysiological examination of ink motor neuron activity in response to sustained head shock revealed an accelerating spike train. During the later part of the spike train, compound excitatory synaptic potentials show a positive shift in reversal potential. 5. Our results suggest a central locus for the mechanisms that determine sensitivity of inking behavior to stimulus duration. 6. In contrast to ink release, defensive gill withdrawal was found to be extremely sensitive to short-duration stimuli.

A mechanism for production of phase shifts in a pattern generator

1984 ◽  
Vol 51 (6) ◽  
pp. 1375-1393 ◽  
Author(s):  
J. S. Eisen ◽  
E. Marder
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Phase Relations ◽  
Significant Advance ◽  
Neuron Activity ◽  
Cycle Frequency ◽  
Bath Application ◽  
Pyloric Dilator ◽  
Wide Range ◽  
Post Synaptic Potential

During motor activity of the pyloric system of the lobster stomatogastric ganglion, there are rhythmic alternations between activity in the pyloric dilator (PD) and pyloric (PY) motor neurons. We studied the phase relations between PD motor neuron activity and PY motor neuron activity in preparations cycling at a wide range of frequencies and after altering the activity of the PD neurons. The PY neurons fall into two classes, early (PE) and late (PL) (21), distinguished by the different phases in the pyloric cycle at which they fire. The phase at which PE neurons fired and the phase at which PL neurons fired was independent of pyloric cycle frequency over a range of frequencies from 0.5 to 2.25 Hz. The anterior burster (AB) interneuron is electrically coupled to the PD motor neurons. Together the AB and PD neurons form the pacemaker for the pyloric system. Synchronous depolarization of the AB and PD neurons evokes a complex inhibitory post-synaptic potential (IPSP) in PY neurons. This IPSP has two components: an early, AB neuron-derived component and a late, PD neuron-derived component. Deletion of the PD neurons from the pyloric circuit by photoinactivation removed the PD-evoked component of the pacemaker-evoked IPSP. This resulted in a decrease in the duration of the IPSP evoked by pacemaker depolarization and a significant advance in the firing phase of PY neurons. Bath application of dopamine was used to hyperpolarize and inhibit the PD neurons (30), causing them to release less neurotransmitter. As a consequence, the duration of the IPSP evoked by pacemaker depolarization was decreased and the firing phase of the PY neurons was significantly advanced. Stimulation of the inferior ventricular nerve (IVN) produces a slow excitation of the PD neurons (30), causing them to release more neurotransmitter. Consequently, the duration of the IPSP evoked by pacemaker depolarization was increased and the firing phase of the PY neurons was significantly retarded for several cycles of pyloric activity following IVN stimulation. Thus, modulation of the strength of PD-evoked inhibition in PY neurons is responsible for altering the firing phase of the PY neurons with respect to the pyloric pacemaker. We suggest that frequency of the pyloric output and the phase relations of the elements within the pyloric cycle can be regulated independently. The potential implications of these data for modulation of synaptic efficacy in other preparations are discussed.

Glutamatergic N2v Cells Are Central Pattern Generator Interneurons of the Lymnaea Feeding System: New Model for Rhythm Generation

1997 ◽  
Vol 78 (6) ◽  
pp. 3396-3407 ◽  
Author(s):  
M. J. Brierley ◽  
M. S. Yeoman ◽  
P. R. Benjamin
Keyword(s):  
Central Pattern Generator ◽  
Synaptic Connection ◽  
Giant Cells ◽  
Pattern Generator ◽  
Synaptic Connections ◽  
Rhythm Generation ◽  
Feeding System ◽  
New Model ◽  
Feeding Cycle ◽  
Protraction Phase

Brierley, M. J., M. S. Yeoman, and P. R. Benjamin. Glutamatergic N2v cells are central pattern generator interneurons of the Lymnaea feeding system: new model for rhythm generation. J. Neurophysiol. 78: 3396–3407, 1997. We aimed to show that the paired N2v (N2 ventral) plateauing cells of the buccal ganglia are important central pattern generator (CPG) interneurons of the Lymnaea feeding system. N2v plateauing is phase-locked to the rest of the CPG network in a slow oscillator (SO)-driven fictive feeding rhythm. The phase of the rhythm is reset by artificially evoked N2v bursts, a characteristic of CPG neurons. N2v cells have extensive input and output synaptic connections with the rest of the CPG network and the modulatory SO cell and cerebral giant cells (CGCs). Synaptic input from the protraction phase interneurons N1M (excitatory), N1L (inhibitory), and SO (inhibitory-excitatory) are likely to contribute to a ramp-shaped prepotential that triggers the N2v plateau. The prepotential has a highly complex waveform due to progressive changes in the amplitude of the component synaptic potentials. Most significant is the facilitation of the excitatory component of the SO → N2v monosynaptic connection. None of the other CPG interneurons has the appropriate input synaptic connections to terminate the N2v plateaus. The modulatory function of acetylcholine (ACh), the transmitter of the SO and N1M/N1Ls, was examined. Focal application of ACh (50-ms pulses) onto the N2v cells reproduced the SO → N2v biphasic synaptic response but also induced long-term plateauing (20–60 s). N2d cells show no endogenous ability to plateau, but this can be induced by focal applications of ACh. The N2v cells inhibit the N3 tonic (N3t) but not the N3 phasic (N3p) CPG interneurons. The N2v → N3t inhibitory synaptic connection is important in timing N3t activity. The N3t cells recover from this inhibition and fire during the swallow phase of the feeding pattern. Feedback N2v inhibition to the SO, N1L protraction phase interneurons prevents them firing during the retraction phase of the feeding cycle. The N2v → N1M synaptic connection was weak and only found in 50% of preparations. A weak N2v → CGC inhibitory connection prevents the CGCs firing during the rasp (N2) phase of the feeding cycle. These data allowed a new model for the Lymnaea feeding CPG to be proposed. This emphasizes that each of the six types of CPG interneuron has a unique set of synaptic connections, all of which contribute to the generation of a full CPG pattern.

Control of stepping velocity in a single insect leg during walking

2006 ◽  
Vol 365 (1850) ◽  
pp. 251-271 ◽  
Author(s):  
Jens Peter Gabriel ◽  
Ansgar Büschges
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Stance Phase ◽  
Close Correlation ◽  
Stick Insect ◽  
Neuron Activity ◽  
Cycle Period ◽  
Velocity Changes ◽  
Single Insect ◽  
Phase Activity

In the single middle leg preparation of the stick insect walking on a treadmill, the activity of flexor and extensor tibiae motor neurons and muscles, which are responsible for the movement of the tibia in stance and swing phases, respectively, was investigated with respect to changes in stepping velocity. Changes in stepping velocity were correlated with cycle period. There was a close correlation of flexor motor neuron activity (stance phase) with stepping velocity, but the duration and activation of extensor motor neurons (swing phase) was not altered. The depolarization of flexor motor neurons showed two components. At all step velocities, a stereotypic initial depolarization was generated at the beginning of stance phase activity. A subsequent larger depolarization and activation was tightly linked to belt velocity, i.e. it occurred earlier and with larger amplitude during fast steps compared with slow steps. Alterations in a tonic background excitation appear not to play a role in controlling the motor neuron activity for changes in stepping velocity. Our results indicate that in the single insect leg during walking, mechanisms for altering stepping velocity become effective only during an already ongoing stance phase motor output. We discuss the putative mechanisms involved.

Three forms of the scratch reflex in the spinal turtle: central generation of motor patterns

1985 ◽  
Vol 53 (6) ◽  
pp. 1517-1534 ◽  
Author(s):  
G. A. Robertson ◽  
L. I. Mortin ◽  
J. Keifer ◽  
P. S. Stein
Keyword(s):  
Spinal Cord ◽  
Motor Neuron ◽  
Neuromuscular Blockade ◽  
Motor Neurons ◽  
Muscle Activity ◽  
Activity Patterns ◽  
Knee Extensor ◽  
The Body ◽  
Retractor Muscle ◽  
Neuron Activity

A turtle with a complete transection of the spinal cord, termed a spinal turtle, exhibits three types or “forms” of the scratch reflex: the rostral scratch, pocket scratch, and caudal scratch (21). Each scratch form is elicited by tactile stimulation of a site on the body surface innervated by afferents entering the spinal cord caudal to the transection. We recorded electromyographic (EMG) potentials from the hindlimb during each of the three forms of the scratch in the spinal turtle (see Fig. 1). Common to all scratch forms is the rhythmic alternation of the activity of the hip protractor muscle (VP-HP) and hip retractor muscle (HR-KF). Each form of the scratch displays a characteristic timing of the activity of the knee extensor muscle (FT-KE) with respect to the cycle of activity of the hip muscles VP-HP and HR-KF. In a rostral scratch, activation of FT-KE occurs during the latter portion of VP-HP activation. In a pocket scratch, activation of FT-KE occurs during HR-KF activation. In a caudal scratch, activation of FT-KE occurs after the cessation of HR-KF activation. The timing characteristics of these muscle activity patterns correspond to the timing characteristics of changes in the angles of the knee joint and the hip joint obtained with movement analyses (21). We recorded electroneurographic (ENG) potentials from peripheral nerves of the hindlimb during each of the three forms of the “fictive” scratch in the spinal turtle immobilized with neuromuscular blockade (see Fig. 4). Common to all forms of the fictive scratch is the rhythmic alternation of the activity of hip protractor motor neurons (VP-HP) and hip retractor motor neurons (HR-KF). Each form displays a characteristic timing of the activity of knee extensor motor neurons (FT-KE) with respect to the cycle of VP-HP and HR-KF motor neuron activity. The timing characteristics of these motor neuron activity patterns are similar to the timing characteristics of the muscle activity patterns obtained in the preparation with movement (cf. Figs. 1 and 4). The motor pattern for each scratch form is generated centrally within the spinal cord. In the spinal immobilized preparation, neuromuscular blockade prevents both limb movement and phasic sensory input, and complete spinal transection isolates the cord from supraspinal input.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Human genetics and neuropathology suggest a link between miR-218 and amyotrophic lateral sclerosis pathophysiology

2019 ◽  
Vol 11 (523) ◽  
pp. eaav5264 ◽  
Author(s):  
Irit Reichenstein ◽  
Chen Eitan ◽  
Sandra Diaz-Garcia ◽  
Guy Haim ◽  
Iddo Magen ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Motor Neuron ◽  
Motor Neuron Disease ◽  
Motor Neurons ◽  
Neuron Activity ◽  
Mouse Development ◽  
Healthy Human ◽  
Mrna Targets ◽  
Human Motor ◽  
Lateral Sclerosis

Motor neuron–specific microRNA-218 (miR-218) has recently received attention because of its roles in mouse development. However, miR-218 relevance to human motor neuron disease was not yet explored. Here, we demonstrate by neuropathology that miR-218 is abundant in healthy human motor neurons. However, in amyotrophic lateral sclerosis (ALS) motor neurons, miR-218 is down-regulated and its mRNA targets are reciprocally up-regulated (derepressed). We further identify the potassium channel Kv10.1 as a new miR-218 direct target that controls neuronal activity. In addition, we screened thousands of ALS genomes and identified six rare variants in the human miR-218-2 sequence. miR-218 gene variants fail to regulate neuron activity, suggesting the importance of this small endogenous RNA for neuronal robustness. The underlying mechanisms involve inhibition of miR-218 biogenesis and reduced processing by DICER. Therefore, miR-218 activity in motor neurons may be susceptible to failure in human ALS, suggesting that miR-218 may be a potential therapeutic target in motor neuron disease.

Multi-Joint Coordination During Walking and Foothold Searching in the Blaberus Cockroach. II. Extensor Motor Neuron Pattern

2000 ◽  
Vol 83 (6) ◽  
pp. 3337-3350 ◽  
Author(s):  
Andrew K. Tryba ◽  
Roy E. Ritzmann
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Stance Phase ◽  
Phase Relationship ◽  
Neuron Activity ◽  
Step Cycle ◽  
Joint Coordination ◽  
Stick Insects ◽  
Relationship Of ◽  
Tonic Excitation

In a previous study, we combined joint kinematics and electromyograms (EMGs) to examine the change in the phase relationship of two principal leg joints during walking and searching. In this study, we recorded intracellularly from motor neurons in semi-intact behaving animals to examine mechanisms coordinating extension at these leg joints. In particular, we examined the change in the phase of the coxa-trochanter (CTr) and femur-tibia (FT) joint extension during walking and searching. In doing so, we discovered marked similarities in the activity of CTr and FT joint extensor motor neurons at the onset of extension during searching and at the end of stance during walking. The data suggest that the same interneurons may be involved in coordinating the CTr and FT extensor motor neurons during walking and searching. Previous studies in stick insects have suggested that extensor motor neuron activity during the stance phase of walking results from an increase in tonic excitation of the neuron leading to spiking that is periodically interrupted by centrally generated inhibition. However, the CTr and FT extensor motor neuron activity during walking consists of characteristic phasic modulations in motor neuron frequency within each step cycle. The phasic increases and decreases in extensor EMG frequency during stance are associated with kinematic events (i.e., foot set-down and joint cycle transitions) during walking. Sensory feedback associated with these events might be responsible for phasic modulation of the extensor motor neuron frequency. However, our data rule out the possibility that sensory cues resulting from foot set-down are responsible for a decline in CTr extensor activity that is characteristic of the Blaberusstep cycle. Our data also suggest that both phasic excitation and inhibition contribute to extensor motor neuron activity during the stance phase of walking.

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.

scholarly journals Task-dependent modification of leg motor neuron synaptic input underlying changes in walking direction and walking speed

2015 ◽  
Vol 114 (2) ◽  
pp. 1090-1101 ◽  
Author(s):  
Philipp Rosenbaum ◽  
Josef Schmitz ◽  
Joachim Schmidt ◽  
Ansgar Büschges
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Synaptic Input ◽  
Walking Speed ◽  
Vertical Plane ◽  
Stick Insect ◽  
Neuron Activity ◽  
Step Cycle ◽  
Synaptic Inputs ◽  
Dependent Modification

Animals modify their behavior constantly to perform adequately in their environment. In terrestrial locomotion many forms of adaptation exist. Two tasks are changes of walking direction and walking speed. We investigated these two changes in motor output in the stick insect Cuniculina impigra to see how they are brought about at the level of leg motor neurons. We used a semi-intact preparation in which we can record intracellularly from leg motor neurons during walking. In this single-leg preparation the middle leg of the animal steps in a vertical plane on a treadwheel. Stimulation of either abdomen or head reliably elicits fictive forward or backward motor activity, respectively, in the fixed and otherwise deafferented thorax-coxa joint. With a change of walking direction only thorax-coxa-joint motor neurons protractor and retractor changed their activity. The protractor switched from swing activity during forward to stance activity during backward walking, and the retractor from stance to swing. This phase switch was due to corresponding change of phasic synaptic inputs from inhibitory to excitatory and vice versa at specific phases of the step cycle. In addition to phasic synaptic input a tonic depolarization of the motor neurons was present. Analysis of changes in stepping velocity during stance showed only a significant correlation to flexor motor neuron activity, but not to that of retractor and depressor motor neurons during forward walking. These results show that different tasks in the stick insect walking system are generated by altering synaptic inputs to specific leg joint motor neurons only.

Local nonspiking interneurons involved in gating of the descending motor pathway in crayfish

1986 ◽  
Vol 56 (3) ◽  
pp. 718-731 ◽  
Author(s):  
M. Takahata ◽  
M. Hisada
Keyword(s):  
Membrane Potential ◽  
Motor Neuron ◽  
Motor Neurons ◽  
Potential Change ◽  
Neuron Activity ◽  
Membrane Potential Change ◽  
Motor Pathway ◽  
Terminal Ganglion ◽  
Nonspiking Interneurons ◽  
Abdominal Movement

Uropod motor neurons in the terminal abdominal ganglion of crayfish are continuously excited during the abdominal posture movement so that subthreshold excitatory postsynaptic potentials from the descending statocyst pathway can elicit spike activity in the motor neurons only while the abdominal posture system is in operation. Local nonspiking interneurons in the terminal ganglion were also found to show sustained membrane potential change during the fictive abdominal posture movement. Artificial membrane potential change of these interneurons by intracellular current injection in the same direction as that actually observed during the abdominal movement caused similar excitation of uropod motor neurons. Artificial cancellation of the membrane potential change of these interneurons during the abdominal movement also caused cancellation of the excitation of uropod motor neurons. We concluded that the continuous excitation of uropod motor neurons during the fictive abdominal movement was mediated, at least partly, by the local nonspiking interneurons. Fourteen (36%) out of 39 examined nonspiking interneurons were judged to be involved in the excitation of uropod motor neurons during the fictive abdominal movement. Another 25 interneurons (64%) were found not to be involved in the excitation of motor neurons, although most of them had a strong effect on the uropod motor neuron activity when their membrane potential was changed artificially. The interneurons that were involved in the excitation of motor neurons during the abdominal movement included both of the two major structural types of nonspiking interneurons in the terminal ganglion, i.e., those in the anterolateral portion and those in the posterolateral portion. No strict correlation was found between the structure of nonspiking interneurons and their function in the control of uropod motor neuron activity.

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