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.

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.

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.

Cooperative Mechanisms Between Leg Joints of Carausius morosusII. Motor Neuron Activity and Influence of ConditionalBursting Interneuron

1998 ◽  
Vol 79 (6) ◽  
pp. 2977-2985 ◽  
Author(s):  
Dennis E. Brunn ◽  
Antje Heuer
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Lucifer Yellow ◽  
Companion Paper ◽  
Stick Insect ◽  
Neuron Activity ◽  
Local Interneuron ◽  
Metathoracic Ganglion ◽  
Thoracic Part ◽  
Swing Movement

Brunn, Dennis E. and Antje Heuer. Cooperative mechanisms between leg joints of Carausius morosus. II. Motor neuron activity and influence of conditional bursting interneuron. J. Neurophysiol. 79: 2977–2985, 1998. The activity of the motor neuron pools of the protractor coxae muscle and of the thoracic part of the depressor trochanteris muscle during forward walking in the stick insect was investigated, and a spiking local interneuron, able to produce “endogenous bursting” and innervating both motor neuron pools, was identified. Extracellular recordings of the motor neurons innervating the protractor and the thoracic depressor of front, middle, and rear legs, respectively, were made with oil-hook electrodes from the peripheral nerves nl2c and nl4a while the animals were walking on a styrofoam treadwheel. The corresponding leg movements were registered and phase histograms were created with the software Spike2. Intracellular recordings were made in the neuropile of the metathoracic ganglion with glass electrodes filled with the dye Lucifer yellow. In all three legs measured (front, middle, and rear), both motor neuron pools increased their activity during the swing movement. The increase in the activity of the protractor motor neurons started at the end of the stance ∼100 ms before reaching the posterior extreme position (PEP), and the activity of the large-sized depressor motor neurons increased as soon as the tarsus was lifted at the PEP. A local spiking interneuron was identified that excited both motor neuron pools. In 4 of 23 recordings the interneuron started to burst in synchrony with protractor and thoracic depressor motor neurons. During bursting a depolarizing stimulus reinforced and a hyperpolarizing stimulus inhibited the activity of both motor neuron pools. Thus we conclude that the thoracic part of the depressor trochanteris muscle might be a component of the neuromuscular system that shapes the swing movement. The two proximal joints, subcoxal and coxa-trochanter, connected mechanically via the thoracic part of the depressor trochanteris muscle, are also connected neurally by segmental and intersegmental spiking interneurons (this paper) and by nonspiking local interneurons (see companion paper).

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.

scholarly journals Descending octopaminergic neurons modulate sensory-evoked activity of thoracic motor neurons in stick insects

2019 ◽  
Vol 122 (6) ◽  
pp. 2388-2413 ◽  
Author(s):  
Thomas Stolz ◽  
Max Diesner ◽  
Susanne Neupert ◽  
Martin E. Hess ◽  
Estefania Delgado-Betancourt ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Stick Insect ◽  
Neuron Activity ◽  
Sense Organs ◽  
Descending Neurons ◽  
Walking Activity ◽  
Stick Insects ◽  
Evoked Activity ◽  
Sensory Evoked ◽  
Stimulation Of

Neuromodulatory neurons located in the brain can influence activity in locomotor networks residing in the spinal cord or ventral nerve cords of invertebrates. How inputs to and outputs of neuromodulatory descending neurons affect walking activity is largely unknown. With the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and immunohistochemistry, we show that a population of dorsal unpaired median (DUM) neurons descending from the gnathal ganglion to thoracic ganglia of the stick insect Carausius morosus contains the neuromodulatory amine octopamine. These neurons receive excitatory input coupled to the legs’ stance phases during treadmill walking. Inputs did not result from connections with thoracic central pattern-generating networks, but, instead, most are derived from leg load sensors. In excitatory and inhibitory retractor coxae motor neurons, spike activity in the descending DUM (desDUM) neurons increased depolarizing reflexlike responses to stimulation of leg load sensors. In these motor neurons, descending octopaminergic neurons apparently functioned as components of a positive feedback network mainly driven by load-detecting sense organs. Reflexlike responses in excitatory extensor tibiae motor neurons evoked by stimulations of a femur-tibia movement sensor either are increased or decreased or were not affected by the activity of the descending neurons, indicating different functions of desDUM neurons. The increase in motor neuron activity is often accompanied by a reflex reversal, which is characteristic for actively moving animals. Our findings indicate that some descending octopaminergic neurons can facilitate motor activity during walking and support a sensory-motor state necessary for active leg movements. NEW & NOTEWORTHY We investigated the role of descending octopaminergic neurons in the gnathal ganglion of stick insects. The neurons become active during walking, mainly triggered by input from load sensors in the legs rather than pattern-generating networks. This report provides novel evidence that octopamine released by descending neurons on stimulation of leg sense organs contributes to the modulation of leg sensory-evoked activity in a leg motor control system.

Slow Temporal Filtering May Largely Explain the Transformation of Stick Insect (Carausius morosus) Extensor Motor Neuron Activity Into Muscle Movement

2007 ◽  
Vol 98 (3) ◽  
pp. 1718-1732 ◽  
Author(s):  
Scott L. Hooper ◽  
Christoph Guschlbauer ◽  
Géraldine von Uckermann ◽  
Ansgar Büschges
Keyword(s):  
Motor Neuron ◽  
Time Constant ◽  
Time Scale ◽  
Stick Insect ◽  
Neuron Activity ◽  
Temporal Filtering ◽  
Time Constants ◽  
Neural Input ◽  
Spike Number ◽  
Contraction And Relaxation

Understanding how nervous systems generate behavior requires understanding how muscles transform neural input into movement. The stick insect extensor tibiae muscle is an excellent system in which to study this issue because extensor motor neuron activity is highly variable during single leg walking and extensor muscles driven with this activity produce highly variable movements. We showed earlier that spike number, not frequency, codes for extensor amplitude during contraction rises, which implies the muscle acts as a slow filter on the time scale of burst interspike intervals (5–10 ms). We examine here muscle response to spiking variation over entire bursts, a time scale of hundreds of milliseconds, and directly measure muscle time constants. Muscle time constants differ during contraction and relaxation, and contraction time constants, although variable, are always extremely slow (200–700 ms). Models using these data show that extremely slow temporal filtering alone can explain much of the observed transform properties. This work also revealed an unexpected (to us) ability of slow filtering to transform steadily declining inputs into constant amplitude outputs. Examination of the effects of time constant variability on model output showed that variation within an SD primarily altered output amplitude, but variation across the entire range also altered contraction shape. These substantial changes suggest that understanding the basis of this variation is central to predicting extensor activity and that the animal could theoretically vary muscle time constant to match extensor response to changing behavioral need.

Different Motor Neuron Spike Patterns Produce Contractions With Very Similar Rises in Graded Slow Muscles

2007 ◽  
Vol 97 (2) ◽  
pp. 1428-1444 ◽  
Author(s):  
Scott L. Hooper ◽  
Christoph Guschlbauer ◽  
Géraldine von Uckermann ◽  
Ansgar Büschges
Keyword(s):  
Motor Neuron ◽  
Motor Nerve ◽  
Stick Insect ◽  
Spike Frequency ◽  
Neuron Activity ◽  
Number Range ◽  
Neuron Spike ◽  
Extensor Muscles ◽  
Spike Number ◽  
Spike Patterns

Graded muscles produce small twitches in response to individual motor neuron spikes. During the early part of their contractions, contraction amplitude in many such muscles depends primarily on the number of spikes the muscle has received, not the frequency or pattern with which they were delivered. Stick insect ( Carausius morosus) extensor muscles are graded and thus would likely show spike-number dependency early in their contractions. Tonic stimulations of the extensor motor nerve showed that the response of the muscles differed from the simplest form of spike-number dependency. However, these differences actually increased the spike-number range over which spike-number dependency was present. When the motor nerve was stimulated with patterns mimicking the motor neuron activity present during walking, amplitude during contraction rises also depended much more on spike number than on spike frequency. A consequence of spike-number dependency is that brief changes in spike frequency do not alter contraction slope and we show here that extensor motor neuron bursts with different spike patterns give rise to contractions with very similar contraction rises. We also examined in detail the early portions of a large number of extensor motor neuron bursts recorded during single-leg walking and show that these portions of the bursts do not appear to have any common spike pattern. Although alternative explanations are possible, the simplest interpretation of these data is that extensor motor neuron firing during leg swing is not tightly controlled.

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.

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.

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