scholarly journals Central Programming and Reflex Control of Walking in the Cockroach

1972 ◽  
Vol 56 (1) ◽  
pp. 173-193
Author(s):  
K. G. PEARSON
Keyword(s):  
Sensory Input ◽  
Discharge Rate ◽  
Activity Patterns ◽  
Motor Units ◽  
Campaniform Sensilla ◽  
Rhythm Generator ◽  
Freely Moving ◽  
Reflex Control ◽  
Central Rhythm Generator ◽  
Leg Movements

1. The activity in identified motor units supplying the coxal levator and depressor muscles of the cockroach have been recorded in intact freely walking animals and in preparations after removal of all sensory input from leg receptors. 2. Reciprocal activity in levator and depressor motoneurones can be evoked, or occurs spontaneously, in the partially de-afferented preparations, thus indicating the existence of a central locomotory rhythm generator. 3. The reciprocal activity patterns recorded in the same motoneurones in intact freely moving animals are not identical to those recorded in partially de-afferented preparations. Thus, the production of normal rhythmic leg movements depends to some extent on sensory input from leg receptors, this input probably exerting tonic and phasic effects on the central rhythm generator. 4. An increase in the resistance to leg retraction during normal walking results in an increase in discharge rate of the levator and depressor motoneurones. This observation further demonstrates that rhythmic leg movements are not exclusively centrally controlled. The receptors responsible for this reflex effect are probably the trochanteral campaniform sensilla.

Nervous Mechanisms Underlying Intersegmental Co-Ordination of Leg Movements During Walking in the Cockroach

1973 ◽  
Vol 58 (3) ◽  
pp. 725-744
Author(s):  
K. G. PEARSON ◽  
J. F. ILES
Keyword(s):  
Sensory Input ◽  
Walking Speed ◽  
Campaniform Sensilla ◽  
Mutual Inhibition ◽  
Leg Muscles ◽  
Slow Walking ◽  
Tripod Gait ◽  
Walking Speeds ◽  
Generating System ◽  
Leg Movements

1. The activity in identical motoneurones innervating leg muscles of the three thoracic segments of the cockroach has been recorded in (a) normal walking animals, (b) walking animals after lesions to the nervous system and/or amputation of the mesothoracic legs, and (c) restrained de-afferented preparations. 2. The phase of levator motoneurone burst activity of the mesothoracic leg in the metathoracic cycle is almost 0·5 for all walking speeds above 2 steps/sec, confirming that a tripod gait is used at all but the slowest speeds. 3. The burst-generating systems in each segment are centrally coupled because in de-afferented preparations there is a tendency for the bursts in the mesothoraci segment to begin near the end of the metathoracic bursts, and vice versa. 4. Sensory input from leg receptors is also important in co-ordinating stepping movements of the different legs since (a) there are some differences in motoneurone activity of de-afferented and walking preparations, and (b) amputation of the mesothoracic legs at the trochanter leads to an immediate change in the co-ordination of the remaining four legs. 5. It is proposed that two mechanisms are important in co-ordinating leg movements in a slow walking cockroach (a) mutual inhibition between levator burst-generating systems in adjacent ipsilateral legs, and (b) an inhibitory reflex pathway from the campaniform sensilla of the trochanter to the burst-generating system of each leg. The second of these two mechanisms may become less important as the walking speed increases.

The neurophysiology of respiration in decapod crustacea. II. The sensory system

1969 ◽  
Vol 47 (3) ◽  
pp. 435-441 ◽  
Author(s):  
Valerie M. Pasztor
Keyword(s):  
Connective Tissue ◽  
Sensory Input ◽  
Respiratory Rhythm ◽  
Sensory System ◽  
Nerve Fibers ◽  
Rhythm Generator ◽  
Decapod Crustacea ◽  
New Type

The mechanoreceptors of the respiratory appendage were studied by histological and electrophysiological techniques.A new type of mechanoreceptor is described and named the "oval organ". It consists of a specialized oval patch of cuticle 1–2 mm in length which is traversed by a spine or longitudinal thickening. Closely applied to the cuticle is a pad of connective tissue richly supplied with dendrites from two large nerve fibers. The orientation of the spine and the dendrites ensures that the receptor responds preferentially to certain stresses or foldings of the oval organ. It lies at the base of the scaphognathite on the dorsal surface.No internal proprioceptors were observed. Movements of the appendage are signalled either by the oval organ, epidermal receptors, or hair sensilla.The possible effect of sensory input upon the central respiratory rhythm generator is discussed.

Pain-induced changes in motor unit discharge depend on recruitment threshold and contraction speed

2021 ◽  
Author(s):  
Eduardo Martinez-Valdes ◽  
Francesco Negro ◽  
Michail Arvanitidis ◽  
Dario Farina ◽  
Deborah Falla
Keyword(s):  
Discharge Rate ◽  
Tibialis Anterior Muscle ◽  
Maximum Voluntary Contraction ◽  
Motor Units ◽  
Inhibitory Effect ◽  
Voluntary Contraction ◽  
Recruitment Threshold ◽  
Contraction Speed ◽  
Discharge Rates ◽  
Hypertonic Saline Injection

At high forces, the discharge rates of lower and higher threshold motor units (MU) are influenced in a different way by muscle pain. These differential effects may be particularly important for performing contractions at different speeds since the proportion of lower and higher threshold MUs recruited varies with contraction velocity. We investigated whether MU discharge and recruitment strategies are differentially affected by pain depending on their recruitment threshold (RT), across a range of contraction speeds. Participants performed ankle dorsiflexion sinusoidal-isometric contractions at two frequencies (0.25Hz and 1Hz) and two modulation amplitudes [5% and 10% of the maximum voluntary contraction (MVC)] with a mean target torque of 20%MVC. High-density surface electromyography recordings from the tibialis anterior muscle were decomposed and the same MUs were tracked across painful (hypertonic saline injection) and non-painful conditions. Torque variability, mean discharge rate (MDR), DR variability (DRvar), RT and the delay between the cumulative spike train and the resultant torque output (neuromechanical delay, NMD) were assessed. The average RT was greater at faster contraction velocities (p=0.01) but was not affected by pain. At the fastest contraction speed, torque variability and DRvar were reduced (p<0.05) and MDR was maintained. Conversely, MDR decreased and DRvar and NMD increased significantly during pain at slow contraction speeds (p<0.05). These results show that reductions in contraction amplitude and increased recruitment of higher threshold MUs at fast contraction speeds appears to compensate for the inhibitory effect of nociceptive inputs on lower threshold MUs, allowing the exertion of fast submaximal contractions during pain.

Central patterning and reflex control of antennular flicking in the hermit crab Pagurus alaskensis (Benedict)

1975 ◽  
Vol 63 (1) ◽  
pp. 17-32
Author(s):  
P. J. Snow
Keyword(s):  
Hermit Crab ◽  
Functional Significance ◽  
Sensory Feedback ◽  
Sensory Input ◽  
Spike Frequency ◽  
Joint Movement ◽  
Trigger System ◽  
System A ◽  
Joint Flexion ◽  
Reflex Control

1. The effects of altering sensory input on the motoneuronal activity underlying antennular flicking have been tested. 2. Removal of the short segments of the outer flagellum results in a reduction of the number of spikes/burst in the fast flexor motoneurones A31F and A32F. 3. During a flick the delay between the burst in motoneurone A31F and the burst in motoneurone A32F is insensitive to alteration of sensory input. 4. Sensory feedback from the flexion phase of a flick is necessary for the activation of either extensor motoneurone. Evidence is presented to suggest that this feedback is primarily from joint-movement receptors at the MS-DS and DS-OF joints. 5. The results are incorporated into a model in which the patterns of flexor activity result from some specified properties of three components: a trigger system, a follower system, and the spike initiating zone of the flexor motoneurones. The trigger system determines when a flick will occur. The follower system determines the number of flexor spikes during a flick. Properties of the spike initiating zone determine the spike frequency and the timing between bursts in the flexor motoneurones. Extensor activity in the model is reflexively elicited by feedback from phasic, unidirectional receptors sensitive to joint flexion. 6. The functional significance of reflex control of extensor activity is discussed in relation to the form and proposed function of antennular flicking. It is suggested that this form of control is adapted to the function of antennular flicking because flexion at the MS-DS joint is not always necessary for the fulfilment of the fuction of a flick.

Ankle Angle but Not Knee Angle Influences Force Fluctuations During Plantar Flexion

2021 ◽  
Author(s):  
Georgios Trypidakis ◽  
Ioannis G. Amiridis ◽  
Roger Enoka ◽  
Irini Tsatsaki ◽  
Eleftherios Kellis ◽  
...  
Keyword(s):  
Knee Joint ◽  
Coefficient Of Variation ◽  
Discharge Rate ◽  
Dominant Role ◽  
Plantar Flexion ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Knee Angle ◽  
Plantar Flexors ◽  
Ankle Angle

AbstractThe purpose of the study was to evaluate the influence of changes in ankle- and knee-joint angles on force steadiness and the discharge characteristics of motor units (MU) in soleus when the plantar flexors performed steady isometric contractions. Submaximal contractions (5, 10, 20, and 40% of maximum) were performed at two ankle angles (75° and 105°) and two knee angles (120° and 180°) by 14 young adults. The coefficient of variation of force decreased as the target force increased from 5 to 20% of maximal force, then remained unaltered at 40%. Independently of knee angle, the coefficient of variation for force at the ankle angle of 75° (long length) was always less (p<0.05) than that at 105° (shorter length). Mean discharge rate, discharge variability, and variability in neural activation of soleus motor units were less (p<0.05) at the 75° angle than at 105°. It was not possible to record MUs from medial gastrocnemius at the knee angle of 120° due to its minimal activation. The changes in knee-joint angle did not influence any of the outcome measures. The findings underscore the dominant role of the soleus muscle in the control of submaximal forces produced by the plantar flexor muscles.

Discharge Patterns of Coxal Levator and Depressor Motoneurones of the Cockroach, Periplaneta Americana

1970 ◽  
Vol 52 (1) ◽  
pp. 139-165
Author(s):  
K. G. PEARSON ◽  
J. F. ILES
Keyword(s):  
Peripheral Nerves ◽  
Sensory Input ◽  
Periplaneta Americana ◽  
Motor Axon ◽  
Extracellular Recordings ◽  
Before And After ◽  
Collateral Pathways ◽  
Discharge Patterns ◽  
Flexion And Extension ◽  
Leg Movements

1. Observation of movements of the metathoracic legs of the cockroach before and after section of peripheral nerves allowed identification of muscles involved in flexion and extension of the femur. 2. Extracellular recordings from the nerves to these coxal muscles show that during rhythmic leg movements bursts of activity in a number of levator motor axons were strongly reciprocal and generally non-overlapping with those of a slow depressor motor axon. 3. These reciprocal patterns persisted after removal of all sensory input from the legs. 4. The durations of levator bursts were relatively constant compared to those of the depressor, corresponding to the behavioural observations on leg protraction time. The pattern was asymmetric: levator bursts could be generated without depressor activity, but never the reverse. 5. No evidence was found for inhibitory collateral pathways between antagonist motoneurones. 6. It is proposed that levator motoneurones are driven by a group of bursting interneurones which simultaneously inhibit the ongoing depressor activity.

Continuous Tonic Spike Activity in Spider Warm Cells in the Absence of Sensory Input

2006 ◽  
Vol 96 (3) ◽  
pp. 989-997 ◽  
Author(s):  
E. Gingl ◽  
H. Tichy
Keyword(s):  
Electrical Stimulation ◽  
Sensory Input ◽  
Discharge Rate ◽  
Rate Of Change ◽  
Intrinsic Properties ◽  
Response Curves ◽  
Temperature Changes ◽  
Different Temperatures ◽  
Low Amplitude ◽  
The Relationship

The warm cells of the spider tarsal organ respond very sensitively to low-amplitude changes in temperature and discharge continuously as the rate of change in temperature reaches zero. To test whether the continuous tonic discharge remains without sensory input, we blocked the warm cell's receptive region by Epoxy glue. The activity continued in this situation, but its dependence on temperature changes was strongly reduced. We interpret this to mean that the warm cells exhibit specific intrinsic properties that underlie the generation of the tonic discharge. Experiments with electrical stimulation confirmed the observation that the warm cells persist in activity without an external drive. In warm cells with blocked receptive region, the response curves describing the relationship between the tonic discharge and the level of depolarization is the same for different temperatures. In warm cells with intact receptive region, the curves are shifted upward with rising temperature, as if the injected current is simply added to the receptor current. This indicates a modulating effect of the receptor current on the tonic discharge. Stimulation causes a change in the tonic discharge rate and thereby enables individual warm cells to signal the direction in addition to the magnitude of temperature changes.

scholarly journals Motor unit contributions to activation reduction and torque steadiness following active lengthening: a study of residual torque enhancement

2020 ◽  
Vol 123 (6) ◽  
pp. 2209-2216 ◽  
Author(s):  
Jennifer M. Jakobi ◽  
Samantha L. Kuzyk ◽  
Chris J. McNeil ◽  
Brian H. Dalton ◽  
Geoffrey A. Power
Keyword(s):  
Motor Unit ◽  
Discharge Rate ◽  
Motor Units ◽  
Electromyographic Activity ◽  
Torque Capacity ◽  
Active Motor ◽  
Motor Neuron Pool ◽  
Acute Condition ◽  
The Impact ◽  
Neuron Pool

Our findings indicate that lower electromyographic activity during the torque-enhanced condition following active lengthening compared with a purely isometric contraction arises from fewer active motor units and a lower discharge rate of those that are active. We used an acute condition of increased torque capacity to induce a decrease in net output of the motor neuron pool during a submaximal task to demonstrate, in humans, the impact of motor unit activity on torque steadiness.

Change in Muscle Fascicle Length Influences the Recruitment and Discharge Rate of Motor Units During Isometric Contractions

2005 ◽  
Vol 94 (5) ◽  
pp. 3126-3133 ◽  
Author(s):  
Benjamin Pasquet ◽  
Alain Carpentier ◽  
Jacques Duchateau
Keyword(s):  
Motor Unit ◽  
Ankle Joint ◽  
Discharge Rate ◽  
Motor Units ◽  
Motor Unit Recruitment ◽  
Isometric Contractions ◽  
Neutral Position ◽  
Proprioceptive Information ◽  
Fascicle Length ◽  
Muscle Fascicle

This study examines the effect of fascicle length change on motor-unit recruitment and discharge rate in the human tibialis anterior (TA) during isometric contractions of various intensities. The torque produced during dorsiflexion and the surface and intramuscular electromyograms (EMGs) from the TA were recorded in eight subjects. The behavior of the same motor unit ( n = 59) was compared at two ankle joint angles (+10 and −10° around the ankle neutral position). Muscle fascicle length of the TA was measured noninvasively using ultrasonography recordings. When the ankle angle was moved from 10° plantarflexion to 10° dorsiflexion, the torque produced during maximal voluntary contraction (MVC) was significantly reduced [35.2 ± 3.3 vs. 44.3 ± 4.2 (SD) Nm; P < 0.001] and the average surface EMG increased (0.47 ± 0.08 vs. 0.43 ± 0.06 mV; P < 0.05). At reduced ankle joint angle, muscle fascicle length declined by 12.7% ( P < 0.01) at rest and by 18.9% ( P < 0.001) during MVC. Motor units were activated at a lower recruitment threshold for short compared with long muscle fascicle length, either when expressed in absolute values (2.1 ± 2.5 vs. 3.6 ± 3.7 Nm; P < 0.001) or relative to their respective MVC (5.2 ± 6.1 vs. 8.8 ± 9.0%). Higher discharge rate and additional motor-unit recruitment were observed at a given absolute or relative torque when muscle fascicles were shortened. However, the data indicate that increased rate coding was mainly present at low torque level (<10% MVC), when the muscle-tendon complex was compliant, whereas recruitment of additional motor units played a dominant role at higher torque level and decreased compliance (10–35% MVC). Taken together, the results suggest that the central command is modulated by the afferent proprioceptive information during submaximal contractions performed at different muscle fascicle lengths.

Spike-triggered average torque and muscle fiber conduction velocity of low-threshold motor units following submaximal endurance contractions

2005 ◽  
Vol 98 (4) ◽  
pp. 1495-1502 ◽  
Author(s):  
Dario Farina ◽  
Lars Arendt-Nielsen ◽  
Thomas Graven-Nielsen
Keyword(s):  
Action Potential ◽  
Motor Unit ◽  
Conduction Velocity ◽  
Surface Potential ◽  
Muscle Fiber ◽  
Discharge Rate ◽  
Motor Units ◽  
Muscle Fiber Conduction Velocity ◽  
Sustained Contraction ◽  
Low Threshold

The motor unit twitch torque is modified by sustained contraction, but the association to changes in muscle fiber electrophysiological properties is not fully known. Thus twitch torque, muscle fiber conduction velocity, and action potential properties of single motor units were assessed in 11 subjects following an isometric submaximal contraction of the tibialis anterior muscle until endurance. The volunteers activated a target motor unit at the minimum discharge rate in eight 3-min-long contractions, three before and five after an isometric contraction at 40% of the maximal torque, sustained until endurance. Multichannel surface electromyogram signals and joint torque were averaged with the target motor unit potential as trigger. Discharge rate (mean ± SE, 6.6 ± 0.2 pulses/s) and interpulse interval variability (33.3 ± 7.0%) were not different in the eight contractions. Peak twitch torque and recruitment threshold increased significantly (93 ± 29 and 12 ± 5%, P < 0.05) in the contraction immediately after the endurance task with respect to the preendurance values (0.94 ± 0.26 mN·m and 3.7 ± 0.5% of the maximal torque), whereas time to peak of the twitch torque did not change (74.4 ± 10.1 ms). Muscle fiber conduction velocity decreased and action potential duration increased in the contraction after the endurance (6.3 ± 1.8 and 9.8 ± 1.8%, respectively, P < 0.05; preendurance values, 3.9 ± 0.2 m/s and 11.1 ± 0.8 ms), whereas the surface potential peak-to-peak amplitude did not change (27.1 ± 3.1 μV). There was no significant correlation between the relative changes in muscle fiber conduction velocity or surface potential duration and in peak twitch torque ( R2 = 0.04 and 0.10, respectively). In conclusion, modifications in peak twitch torque of low-threshold motor units with sustained contraction are mainly determined by mechanisms not related to changes in action potential shape and in its propagation velocity.

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