An Electromyographic Analysis of the Elevator/Depressor Muscle Motor Programme in the Freely-Walking Scorpion, Paruroctonus Mesaensis

1981 ◽  
Vol 91 (1) ◽  
pp. 165-177
Author(s):  
ROBERT F. BOWERMAN
Keyword(s):  
Neural Control ◽  
Stance Phase ◽  
Burst Duration ◽  
Control Mechanisms ◽  
Step Cycle ◽  
Cycle Times ◽  
Tarsal Claw ◽  
Depressor Muscle ◽  
Electromyographic Analysis ◽  
Motor Programme

Electromyograms from the elevator and depressor muscles, together with tarsal claw receptor activity, were recorded from the fourth legs of freely walking scorpions. The slope of the depressor burst duration versus step cycle time was less for short cycle times, below about 600 ms, than it was for longer cycles. The opposite was true for the elevator burst duration versus step cycle relationship, and the slope for longer cycle times was not significantly different from zero. The switching of motor activity between antagonists at the stance to swing phase transition was different from that of the swing to stance phase. The depressor burst invariably terminated before the elevator burst, while the elevator burst frequently did not terminate until after the depressor burst had begun. A similar asymmetry of the elevator/depressor motor programme has been described for insect and crustacean preparations. The termination of the depressor muscle burst represents the initial peripheral indicator that the decision to step has been made centrally. The latency between the central decision and the time when the leg is lifted, as determined by tarsal claw receptor burst termination, can be as much as 125 ms. This observation is of importance when considering both intrasegmental and intersegmental neural control mechanisms of scorpion locomotion.

Feedback and Feedforward Locomotor Adaptations to Ankle-Foot Load in People With Incomplete Spinal Cord Injury

2010 ◽  
Vol 104 (3) ◽  
pp. 1325-1338 ◽  
Author(s):  
Keith E. Gordon ◽  
Ming Wu ◽  
Jennifer H. Kahn ◽  
Brian D. Schmit
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Neural Control ◽  
Stance Phase ◽  
Single Step ◽  
Control Mechanisms ◽  
Effective Interventions ◽  
Cord Injury ◽  
Locomotor Adaptations ◽  
Limb Load

Humans with spinal cord injury (SCI) modulate locomotor output in response to limb load. Understanding the neural control mechanisms responsible for locomotor adaptation could provide a framework for selecting effective interventions. We quantified feedback and feedforward locomotor adaptations to limb load modulations in people with incomplete SCI. While subjects airstepped (stepping performed with kinematic assistance and 100% bodyweight support), a powered-orthosis created a dorisflexor torque during the “stance phase” of select steps producing highly controlled ankle-load perturbations. When given repetitive, stance phase ankle-load, the increase in hip extension work, 0.27 J/kg above baseline (no ankle-load airstepping), was greater than the response to ankle-load applied during a single step, 0.14 J/kg ( P = 0.029). This finding suggests that, at the hip, subjects produced both feedforward and feedback locomotor modulations. We estimate that, at the hip, the locomotor response to repetitive ankle-load was modulated almost equally by ongoing feedback and feedforward adaptations. The majority of subjects also showed after-effects in hip kinetic patterns that lasted 3 min in response to repetitive loading, providing additional evidence of feedforward locomotor adaptations. The magnitude of the after-effect was proportional to the response to repetitive ankle-foot load ( R2= 0.92). In contrast, increases in soleus EMG amplitude were not different during repetitive and single-step ankle-load exposure, suggesting that ankle locomotor modulations were predominately feedback-based. Although subjects made both feedback and feedforward locomotor adaptations to changes in ankle-load, between-subject variations suggest that walking function may be related to the ability to make feedforward adaptations.

The Exoskeleton and Insect Proprioception: III. Activity of Tribal Campaniform Sensilla During Walking in the American Cockroach, Periplaneta Americana

1981 ◽  
Vol 94 (1) ◽  
pp. 57-75
Author(s):  
SASHA N. ZILL ◽  
DAVID T. MORAN
Keyword(s):  
Stance Phase ◽  
Periplaneta Americana ◽  
Specific Activity ◽  
Firing Frequency ◽  
American Cockroach ◽  
Campaniform Sensilla ◽  
Afferent Activity ◽  
Step Cycle ◽  
Slow Walking ◽  
Oriented Parallel

1. In the cockroach tibia, the activities of campaniform sensilla that monitor cuticular strain have been recorded in free-walking animals. 2. In walking, sensillum firing is correlated with myographic activity of the flexor and extensor tibiae muscles. 3. The specific activity of a single campaniform sensillum depends upon the orientation of its cuticular cap. 4. In slow walking, proximal sensilla, whose ovoid cuticular caps are oriented perpendicular to the leg long axis, fire in bursts that are initiated just prior to the onset of extensor tibiae activity in the stance phase of locomotion. The firing frequency within bursts of proximal sensilla is generally inversely related to the frequency of the slow extensor tibiae motoneurone and ceases when motoneurone activity exceeds 200 Hz. 5. Distal campaniform sensilla, oriented parallel to the leg long axis, only fire when slow extensor tibiae activity exceeds 300 Hz. In slow walking, distal sensillum activity typically occurs as a short intense burst near the end of the stance phase of the step cycle, when slow extensor frequency is maximal. Distal sensillum firing is greatly increased when forward progression is impeded. 6. The patterns of afferent activity seen in slow walking indicate that the campaniform sensilla function in load compensation and limitation of muscle tensions. The proximal sensilla respond to initial loading of the leg and can reflexly excite the slow extensor motoneurone in compensation. The distal sensilla respond to cuticular strains that result from large extensor contractions and can reflexly inhibit the slow motoneurone. 7. In rapid walking, activities of both subgroups of campaniform sensilla shift in phase relative to slow extensor firing. Proximal sensilla activity occurs after the onset of slow extensor firing. Distal sensilla bursts follow the termination of slow extensor activity. 8. These phase shifts limit the reflex functions of the tibial campaniform sensilla in rapid walking. Shifts in phase of afferent activity may contribute to the need for central programming of locomotion.

Resituating cognitive mechanisms within heterarchical networks controlling physiology and behavior

2019 ◽  
Vol 29 (5) ◽  
pp. 620-639 ◽  
Author(s):  
William Bechtel
Keyword(s):  
Cognitive Control ◽  
Cognitive Science ◽  
Neural Control ◽  
Science Research ◽  
Control Mechanisms ◽  
Cognitive Mechanisms ◽  
Physiological Processes ◽  
High Level ◽  
And Behavior ◽  
Production Mechanisms

Cognitive science has traditionally focused on mechanisms involved in high-level reasoning and problem-solving processes. Such mechanisms are often treated as autonomous from but controlling underlying physiological processes. I offer a different perspective on cognition which starts with the basic production mechanisms through which organisms construct and repair themselves and navigate their environments and then I develop a framework for conceptualizing how cognitive control mechanisms form a heterarchical network that regulates production mechanisms. Many of these control mechanisms perform cognitive tasks such as evaluating circumstances and making decisions. Cognitive control mechanisms are present in individual cells, but in metazoans, intracellular control is supplemented by a nervous system in which a multitude of neural control mechanisms are organized heterarchically. On this perspective, high-level cognitive mechanisms are not autonomous, but are elements in larger heterarchical networks. This has implications for future directions in cognitive science research.

Corrective responses to loss of ground support during walking. I. Intact cats

1994 ◽  
Vol 71 (2) ◽  
pp. 603-610 ◽  
Author(s):  
M. A. Gorassini ◽  
A. Prochazka ◽  
G. W. Hiebert ◽  
M. J. Gauthier
Keyword(s):  
Stance Phase ◽  
Afferent Input ◽  
Emg Activity ◽  
Step Cycle ◽  
Trap Door ◽  
Ground Support ◽  
Extensor Muscles ◽  
Activation Profile ◽  
Corrective Response ◽  
Hindlimb Kinematics

1. In the cat step cycle the electromyographic (EMG) activity in ankle extensor muscles commences approximately 70 ms before foot contact. There is a sharp peak between 10 and 25 ms after contact and the EMG then declines for the remainder of the stance phase. It has been posited that the abrupt transition in EMG after contact is the consequence of reflexes elicited by the large barrage of afferent input that signals foot touchdown. However, it is also possible that the basic profile might be generated within the CNS, with little modification by afferent input. 2. These ideas were tested in 11 normal cats. We compared EMG responses and hindlimb kinematics in steps with normal ground support and steps in which an actuator-controlled trap door unexpectedly opened, withdrawing ground support just before foot contact. 3. In the absence of ground support the transition in EMG activity was still present. The averaged EMG pattern was similar for at least 30 ms after the foot passed through the plane of the floor. We conclude that the basic extensor activation profile in this part of the cycle is generated centrally and is not substantially altered by afferent input. 4. Between 35 and 200 ms after contact the stance phase was aborted and the foot was lifted smartly out of the hole. This reaction varied both in latency and kinematic detail, suggesting a fairly complex corrective response.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of hind limb flexor muscle afferents to the timing of phase transitions in the cat step cycle

1996 ◽  
Vol 75 (3) ◽  
pp. 1126-1137 ◽  
Author(s):  
G. W. Hiebert ◽  
P. J. Whelan ◽  
A. Prochazka ◽  
K. G. Pearson
Keyword(s):  
Electrical Stimulation ◽  
Stance Phase ◽  
Flexor Muscle ◽  
Step Cycle ◽  
Locomotor Rhythm ◽  
Ia Afferents ◽  
Group I ◽  
Flexor Muscles ◽  
Group Ii ◽  
Stimulation Of

1. In this investigation, we tested the hypothesis that muscle spindle afferents signaling the length of hind-leg flexor muscles are involved in terminating extensor activity and initiating flexion during walking. The hip flexor muscle iliopsoas (IP) and the ankle flexors tibialis anterior (TA) and extensor digitorum longus (EDL) were stretched or vibrated at various phases of the step cycle in spontaneously walking decerebrate cats. Changes in electromyogram amplitude, duration, and timing were then examined. The effects of electrically stimulating group I and II afferents in the nerves to TA and EDL also were examined. 2. Stretch of the individual flexor muscles (IP, TA, or EDL) during the stance phase reduced the duration of extensor activity and promoted the onset of flexor burst activity. The contralateral step cycle also was affected by the stretch, the duration of flexor activity being shortened and extensor activity occurring earlier. Therefore, stretch of the flexor muscles during the stance phase reset the locomotor rhythm to flexion ipsilaterally and extension contralaterally. 3. Results of electrically stimulating the afferents from the TA and EDL muscles suggested that different groups of afferents were responsible for the resetting of the step cycle. Stimulation of the TA nerve reset the locomotor step cycle when the stimulus intensity was in the group II range (2-5 xT). By contrast, stimulation of the EDL nerve generated strong resetting of the step cycle in the range of 1.2-1.4 xT, where primarily the group Ia afferents from the muscle spindles would be activated. 4. Vibration of IP or EDL during stance reduced the duration of the extensor activity by similar amounts to that produced by muscle stretch or by electrical stimulation of EDL at group Ia strengths. This suggests that the group Ia afferents from IP and EDL are capable of resetting the locomotor pattern generator. Vibration of TA did not affect the locomotor rhythm. 5. Stretch of IP or electrical stimulation of TA afferents (5 xT) during the flexion phase did not change the duration of the flexor activity. Stimulation of the EDL nerve at 1.8-5 xT during flexion increased the duration of the flexor activity. In none of our preparations did we observe resetting to extension when the flexor afferents were activated during flexion. 6. We conclude that as the flexor muscles lengthen during the stance phase of gait, their spindle afferents (group Ia afferents for EDL and IP, group II afferents for TA) act to inhibit the spinal center generating extensor activity thus facilitating the initiation of swing.

scholarly journals H-Reflex Modulation During Walking in Spastic Paretic Subjects

1991 ◽  
Vol 18 (4) ◽  
pp. 443-452 ◽  
Author(s):  
J.F. Yang ◽  
J. Fung ◽  
M. Edamura ◽  
R. Blunt ◽  
R.B. Stein ◽  
...  
Keyword(s):  
Tibialis Anterior ◽  
Stance Phase ◽  
Normal Subjects ◽  
Swing Phase ◽  
H Reflex ◽  
Reflex Modulation ◽  
Healthy Individuals ◽  
Step Cycle ◽  
Common Pattern ◽  
Slight Depression

ABSTRACT:Hoffmann (H) reflexes were elicited from the soleus muscle during treadmill walking in 21 spastic paretic patients. The soleus and tibialis anterior muscles were reciprocally activated during walking in most patients, much like that observed in healthy individuals. The pattern of H-reflex modulation varied considerably between patients, from being relatively normal in some patients to a complete absence of modulation in others. The most common pattern observed was a lack of H-reflex modulation through the stance phase and slight depression of the reflex in the swing phase, considerably less modulation than that of normal subjects under comparable walking conditions. The high reflex amplitudes during periods of the step cycle such as early stance seems to be related to the stretch-induced large electromyogram bursts in the soleus in some subjects. The abnormally active reflexes appear to contribute to the clonus encountered during walking in these patients. In three patients who were able to walk for extended periods, the effect of stimulus intensity was examined. Two of these patients showed a greater degree of reflex modulation at lower stimulus intensities, suggesting that the lack of modulation observed at higher stimulus intensities is a result of saturation of the reflex loop. In six other patients, however, no reflex modulation could be demonstrated even at very low stimulus intensities.

scholarly journals Knee mechanisms for through-knee prostheses

1983 ◽  
Vol 7 (2) ◽  
pp. 107-112 ◽  
Author(s):  
K. Öberg
Keyword(s):  
Stance Phase ◽  
Stability Diagram ◽  
Phase Control ◽  
Swing Phase ◽  
Control Mechanisms ◽  
Knee Prostheses ◽  
Heavy Duty ◽  
Linkage Mechanism ◽  
The Stability

The most widely used knee mechanisms for through-knee amputees can be characterized as three principal types of design. These types are metal side bars with heavy duty joints, conventional knee mechanisms for above-knee amputees and special polycentric linkage mechanisms for through-knee amputees. An investigation in Sweden in 1979 showed that over 50% of the fittings were using the special polycentric linkage mechanisms for through-knee amputees. The stability diagram illustrates how voluntary and involuntary stability can be utilized by using different polycentric linkage mechanisms for through-knee amputees. The polycentric linkage mechanism can be designed for different stance phase characteristics as well as incorporation of different swing phase control mechanisms. The cosmesis of the available designs is acceptable but there is need for lighter and more compact designs especially for the young and small amputee.

Autonomic Neural Control Mechanisms and the Release of Adrenal Steroids after Hypoglycaemia in Man

2008 ◽  
Vol 16 (S 1) ◽  
pp. 138-141 ◽  
Author(s):  
B. Frier ◽  
E. A. S. Al-Dujaili ◽  
R. J. M. Corrall ◽  
J. Pritchard ◽  
C. R. W. Edwards
Keyword(s):  
Neural Control ◽  
Control Mechanisms ◽  
Adrenal Steroids

The Human Central Pattern Generator for Locomotion: Does It Exist and Contribute to Walking?

2017 ◽  
Vol 23 (6) ◽  
pp. 649-663 ◽  
Author(s):  
Karen Minassian ◽  
Ursula S. Hofstoetter ◽  
Florin Dzeladini ◽  
Pierre A. Guertin ◽  
Auke Ijspeert
Keyword(s):  
Spinal Cord ◽  
Neural Control ◽  
Muscle Activation ◽  
Central Pattern Generators ◽  
Lumbar Spinal Cord ◽  
Step Cycle ◽  
Experimental Conditions ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Cord Injury

The ability of dedicated spinal circuits, referred to as central pattern generators (CPGs), to produce the basic rhythm and neural activation patterns underlying locomotion can be demonstrated under specific experimental conditions in reduced animal preparations. The existence of CPGs in humans is a matter of debate. Equally elusive is the contribution of CPGs to normal bipedal locomotion. To address these points, we focus on human studies that utilized spinal cord stimulation or pharmacological neuromodulation to generate rhythmic activity in individuals with spinal cord injury, and on neuromechanical modeling of human locomotion. In the absence of volitional motor control and step-specific sensory feedback, the human lumbar spinal cord can produce rhythmic muscle activation patterns that closely resemble CPG-induced neural activity of the isolated animal spinal cord. In this sense, CPGs in humans can be defined by the activity they produce. During normal locomotion, CPGs could contribute to the activation patterns during specific phases of the step cycle and simplify supraspinal control of step cycle frequency as a feedforward component to achieve a targeted speed. Determining how the human CPGs operate will be essential to advance the theory of neural control of locomotion and develop new locomotor neurorehabilitation paradigms.

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