Critical Points in the Forelimb Fictive Locomotor Cycle and Motor Coordination: Effects of Phasic Retractions and Protractions of the Shoulder in the Cat

2004 ◽  
Vol 92 (3) ◽  
pp. 1342-1356 ◽  
Author(s):  
Philippe Saltiel ◽  
Serge Rossignol
Keyword(s):  
Critical Points ◽  
Critical Period ◽  
Motor Coordination ◽  
Companion Paper ◽  
Phase Changes ◽  
Response Patterns ◽  
Feedback Scheme ◽  
Extensor Muscles ◽  
Alternative Responses ◽  
Decerebrate Cats

This study investigates the responses to phasic shoulder retractions or protractions given at different times in the fictive locomotor cycle of the forelimbs of decerebrate cats. Generally, the responses in flexor and extensor muscles acting at the shoulder or elbow were bilaterally coordinated according to a negative feedback scheme. Perturbations in the direction of the movements that would have taken place if the animal had not been paralyzed tended to shorten the duration of the burst of activity of the muscles active during that phase and vice versa in the opposite phase. Changes in response patterns took place around critical points corresponding to the critical points B–D described in the companion paper using tonic perturbations of the limb. Past point C, at 58% of the ipsilateral extensor burst, protractions no longer prolonged the burst and no longer delayed onset of the contralateral extensor. At point B, occurring at 41% of the contralateral extensor burst, ipsilateral protractions maximally shortened the ipsilateral flexor phase, advancing ipsilateral extensor onset (point D) to point C of the contralateral extensor burst. During a critical period from the end of the ipsilateral flexor (point D) until the contralateral flexor onset, retractions elicited two alternative responses. Either the contralateral extensor activity was abolished and the contralateral flexor turned on, or it persisted for another cycle. We argue that the critical points found here correspond to critical biomechanical events in real locomotion and may underlie a phase-dependent motor coordination.

Segmental reflex action in normal and decerebrate cats

1990 ◽  
Vol 64 (5) ◽  
pp. 1611-1624 ◽  
Author(s):  
J. A. Hoffer ◽  
T. R. Leonard ◽  
C. L. Cleland ◽  
T. Sinkjaer
Keyword(s):  
Muscle Length ◽  
Radiant Heat ◽  
Stimulus Onset ◽  
Nerve Cuff ◽  
Reflex Action ◽  
Extensor Muscles ◽  
Before And After ◽  
Force Peak ◽  
Initial Force ◽  
Decerebrate Cats

1. The objective of this study was to evaluate the action of the stretch reflex on the ankle extensor muscles of normal and decerebrate cats. 2. Experiments were performed on nine freely standing, unrestrained cats and repeated after decerebration at the premammillary level. The length, force, and electromyograph (EMG) of the soleus (SOL) and lateral gastrocnemius (LG) muscles were recorded with the use of implanted transducers and electrodes. 3. The left ankle joint was unexpectedly and reproducibly dorsiflexed by briefly stimulating the common peroneal (CP) nerve with electrodes within an implanted nerve cuff. The ensuing twitch contractions of the ankle dorsiflexor muscles stretched the ankle extensor muscles by 0.3-2.0 mm. Lidocaine was infused into another nerve cuff proximal to the stimulation site, to reversibly block the central propagation of evoked volleys in the CP nerve. 4. Reflex action before and after decerebration was measured from the responses to perturbations of similar amplitude and duration delivered at approximately matched background values of muscle length and force. In most cats the temperature of the hindlimb was monitored with an implanted thermistor and was restored to normal values with radiant heat after decerebration. 5. A stretch imposed on the tonically active ankle extensor muscles immediately caused a considerable rise in the force recorded from the triceps tendon. Within 30-40 ms the triceps force peaked, reaching a value 10-20 N greater than background, and then rapidly declined while the extensor muscles were still lengthening. The initial rise in force preceded any change in triceps EMG. It was attributed to the intrinsic viscoelasticity of the stretched muscles and tendons. After decerebration the magnitude and timing of the initial force peak did not change. 6. A short-latency reflex EMG burst was typically recorded from both the SOL and LG muscles, starting 11-17 ms after stimulus onset. After decerebration the area of the reflex EMG burst increased in all nine cats, typically by a factor of 2 or 3. 7. After decerebration a second, smaller increase in force was typically observed starting 60-80 ms after onset of stretch. This later force rise, interpreted to be of reflex origin, was rarely apparent in normal cats. 8. Decerebration introduced consistent modifications in postural behavior that were revealed by pushing down on the back of quietly standing cats. In normal cats, after brief pushes that stretched the ankle extensor muscles by 1-2 mm, the EMG, force, and length quickly stabilized near their initial values.(ABSTRACT TRUNCATED AT 400 WORDS)

Instigation and control of treadmill locomotion in high decerebrate cats by stimulation of the hook bundle of Russell in the cerebellum

2000 ◽  
Vol 78 (11) ◽  
pp. 945-957 ◽  
Author(s):  
Shigemi Mori ◽  
Toshihiro Matsui ◽  
Futoshi Mori ◽  
Katsumi Nakajima ◽  
Kiyoji Matsuyama
Keyword(s):  
Muscle Tone ◽  
Fastigial Nucleus ◽  
Extensor Muscles ◽  
Upper Cervical ◽  
Postural Muscle ◽  
Restricted Region ◽  
Vestibular Complex ◽  
Parallel Activation ◽  
And Control ◽  
Decerebrate Cats

In high decerebrate cats, pulse train microstimulation of a restricted region of the midline cerebellar white matter produced a generalized increase in postural muscle tone in the neck, trunk, and limb extensor muscles, and air-stepping of all four legs on a stationary surface. On the moving belt of a treadmill, such stimulation produced well coordinated, fore- and hindlimb locomotion as evoked by stimulating the mesencephalic locomotor region (MLR). Microinjection of a neural tracer into the cerebellar locomotion-inducing site resulted in a bilateral retrograde labeling of cells limited to the fastigial nuclei simultaneously with anterograde labeling of fibers projecting bilaterally to the medial pontomedullary reticular formation (mPMRF) the vestibular complex and upper cervical segments. These results have led to our proposition that the effective cerebellar locomotor region (CLR) corresponds to the midline region of the hook bundle of Russell. Passing through this structure are crossed fastigioreticular and fastigiovestibular fibers, together with fastigiospinal fibers. Subsequently, we showed that CLR stimulation resulted in simultaneous short-latency synaptic activation of long-descending reticulospinal and vestibulospinal cells with high synaptic security. Clearly, the fastigial nucleus possesses potential capability to recruit and regulate posture- and locomotor-related subprograms which are distributed within the brainstem and spinal cord by the in-parallel activation of fastigiospinal, fastigioreticular, and fastigiovestibular pathways.Key words: cerebellar locomotor region (CLR), fastigial nucleus, hook bundle of Russell, reticulospinal cell, vestibulospinal cell.

Loss of Cochlear Nucleus Neurons following Aminoglycoside Antibiotics or Cochlear Removal

1998 ◽  
Vol 107 (4) ◽  
pp. 337-343 ◽  
Author(s):  
David R. Moore ◽  
Nina J. Rogers ◽  
Stephen J. O'Leary
Keyword(s):  
Cochlear Nucleus ◽  
Critical Period ◽  
Companion Paper ◽  
Afferent Input ◽  
Surgical Ablation ◽  
Auditory Brain Stem Response ◽  
Aminoglycoside Ototoxicity ◽  
Auditory Brain Stem ◽  
Response Thresholds ◽  
Brain Stem Response

This study compared the effects of aminoglycoside ototoxicity and surgical ablation of the cochlea in infancy on the survival of neurons in the rat cochlear nucleus (CN). Ototoxicity was induced by a single, systemic dose of gentamicin sulfate and furosemide on postnatal day 6 (P6), P7, or P10, and assessed by the elevation of auditory brain stem response thresholds, as described in a companion paper. Unilateral cochlear removals were performed under Saffan anesthesia on P6, P9, and P12. Rats were painlessly sacrificed in adulthood, and the formalin-perfused brains and cochleas were embedded in wax, sectioned, and stained. Ototoxic treatment at P6 through P10 did not reduce neuron counts in the CN. Cochlear removal at P6 resulted in a 40% loss of CN neurons, but removal at P12 did not result in CN neuron loss. These data suggest that the critical period for the dependence of CN neurons on afferent input from the cochlea ends at the same time that susceptibility to aminoglycoside ototoxicity begins.

Declining inhibition in ipsi- and contralateral lumbar motoneurons during contractions of an ankle extensor muscle in the cat

1993 ◽  
Vol 70 (5) ◽  
pp. 1797-1804 ◽  
Author(s):  
J. Lafleur ◽  
D. Zytnicki ◽  
G. Horcholle-Bossavit ◽  
L. Jami
Keyword(s):  
Experimental Approach ◽  
Motor Units ◽  
Companion Paper ◽  
Triceps Surae ◽  
Rapid Decline ◽  
Knee Flexor ◽  
Extensor Muscles ◽  
Level 3 ◽  
Tendon Organs ◽  
Group Ii Afferents

1. Motoneurons of pretibial ankle flexor and knee flexor and extensor muscles were recorded intracellularly in chloralose- or pentobarbitone-anesthetized cats during sustained submaximal contractions of either ipsi- or contralateral gastrocnemius medialis muscle (GM). 2. In a majority of ipsilateral motoneurons, a sustained GM contraction elicited inhibitory potentials that quickly subsided before the end of the contraction. An abrupt increase in contractile force could elicit a new series of inhibitory potentials, which declined again in spite of a maintained force level. 3. Contraction-induced effects were only exceptionally detected in contralateral triceps surae and plantaris motoneurons. In a small number of pretibial flexor and knee flexor and extensor motoneurons, declining inhibitions were observed during sustained contractions of the contralateral GM muscle. 4. At the onset of GM contractions, a variety of motoneurons uniformly receive inhibitory inputs that are quickly filtered out. Although the functional significance of this widespread initial inhibition remains to be elucidated, its rapid decline seems useful to allow subsequent recruitment of motor units as may be required for coordination of posture and movement. 5. Tendon organs are activated during muscle contraction, but it is not certain whether Ib inputs from GM can account for all the effects observed. Contribution of other afferents was considered and tested using a different experimental approach. The companion paper reports observations suggesting that effects elicited by group II afferents may cooperate in the contraction-induced inhibition of motoneurons.

Factors determining segmental reflex action in normal and decerebrate cats

1990 ◽  
Vol 64 (5) ◽  
pp. 1625-1635 ◽  
Author(s):  
T. Sinkjaer ◽  
J. A. Hoffer
Keyword(s):  
Muscle Length ◽  
Muscle Spindles ◽  
Radiant Heat ◽  
Companion Paper ◽  
Muscle Afferents ◽  
Short Latency ◽  
Lateral Gastrocnemius ◽  
Implanted Electrodes ◽  
Extensor Muscles ◽  
Before And After

1. In the companion paper the gain of the stretch reflex in the ankle extensor muscles of normal cats was shown to increase after decerebration. The objectives of this study were 1) to identify the origin of the increased reflex and 2) to evaluate the contribution from afferents other than ankle extensor muscle afferents to the short-latency reflex. 2. Six cats were trained to stand unaided on four pedestals. Three cats were also trained to control the force exerted with the left hindlimb. The left soleus (SOL) and lateral gastrocnemius (LG) electromyogram (EMG), length, force, and temperature were recorded by chronically implanted electrodes and transducers. Measurements were taken before and after decerebration at the premammillary level. After decerebration limb temperature was returned to its normal range by the use of radiant heat. 3. Reproducible ramp-and-hold stretches and releases of the ankle extensor muscles were produced by a servo-controlled motor that rotated the left rear pedestal about the ankle joint. The length of the ankle extensor muscles changed by 2-3 mm within 30-35 ms after the onset of a ramp perturbation. Reflex responses before and after decerebration were compared at matched background values of muscle length and force. 4. In both the SOL and LG muscles, a short-latency EMG burst appeared 8-12 ms after stretch onset and lasted approximately 20 ms. After decerebration the onset of the rectified and smoothed EMG burst remained unchanged, but its area was increased by 36-89%. 5. The lateral gastrocnemius-soleus (LG-S) electroneurogram (ENG) was chronically recorded in two cats with a nerve cuff recording electrode implanted on the LG-S nerve. LG-S ENG activity started to increase soon after stretch onset and remained high during the entire ramp phase. The stretch-evoked LG-S ENG burst started approximately 8 ms earlier than the short-latency SOL and LG EMG bursts. It was interpreted to reflect mainly an increase in the activity of Group Ia and Ib muscle afferents, caused by increases in both muscle length and muscle force during the stretch. After the cats were decerebrated, for matched postural conditions, the area of the stretch-evoked LG-S ENG burst was increased by 29-35%. Because the length and force changes sensed by the muscle receptors before and after decerebration were similar, this suggests that the sensitivity of muscle spindles was increased as a consequence of altered activity in fusimotor neurons after decerebration.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Self-reinnervated muscles lose autogenic length feedback, but intermuscular feedback can recover functional connectivity

2016 ◽  
Vol 116 (3) ◽  
pp. 1055-1067 ◽  
Author(s):  
Mark A. Lyle ◽  
Boris I. Prilutsky ◽  
Robert J. Gregor ◽  
Thomas A. Abelew ◽  
T. Richard Nichols
Keyword(s):  
Functional Connectivity ◽  
Stretch Reflex ◽  
Force Feedback ◽  
Spinal Reflex ◽  
Motor Deficits ◽  
Extensor Muscles ◽  
Functional Implications ◽  
Permanent Loss ◽  
Muscle Groups ◽  
Decerebrate Cats

In this study, we sought to identify sensory circuitry responsible for motor deficits or compensatory adaptations after peripheral nerve cut and repair. Self-reinnervation of the ankle extensor muscles abolishes the stretch reflex and increases ankle yielding during downslope walking, but it remains unknown whether this finding generalizes to other muscle groups and whether muscles become completely deafferented. In decerebrate cats at least 19 wk after nerve cut and repair, we examined the influence of quadriceps (Q) muscles' self-reinnervation on autogenic length feedback, as well as intermuscular length and force feedback, among the primary extensor muscles in the cat hindlimb. Effects of gastrocnemius and soleus self-reinnervation on intermuscular circuitry were also evaluated. We found that autogenic length feedback was lost after Q self-reinnervation, indicating that loss of the stretch reflex appears to be a generalizable consequence of muscle self-reinnervation. However, intermuscular force and length feedback, evoked from self-reinnervated muscles, was preserved in most of the interactions evaluated with similar relative inhibitory or excitatory magnitudes. These data indicate that intermuscular spinal reflex circuitry has the ability to regain functional connectivity, but the restoration is not absolute. Explanations for the recovery of intermuscular feedback are discussed, based on identified mechanisms responsible for lost autogenic length feedback. Functional implications, due to permanent loss of autogenic length feedback and potential for compensatory adaptations from preserved intermuscular feedback, are discussed.

Effects on wrist and digit muscle activity from microstimuli applied at the sites of rubromotoneuronal cells in primates

1991 ◽  
Vol 66 (6) ◽  
pp. 1978-1992 ◽  
Author(s):  
P. D. Cheney ◽  
K. Mewes ◽  
G. Widener
Keyword(s):  
Muscle Activity ◽  
Companion Paper ◽  
Emg Activity ◽  
Cell Aggregates ◽  
Onset Latency ◽  
Wrist Movement ◽  
Extensor Muscles ◽  
The Difference ◽  
Stimulus Triggered Averaging ◽  
Forearm Flexor

1. The purpose of this study was to use the techniques of spike- and stimulus-triggered averaging (SpTA and StTA, respectively) to examine the output organization of individual rubromotoneuronal (RM) cells in relation to clusters of neighboring cells. SpTA of electromyographic (EMG) activity in awake monkeys reveals the target muscles of an individual recorded neuron, whereas StTA reveals the target muscles of the neuronal aggregate activated by the stimulus. 2. Three questions were of particular interest. First, does the pattern of poststimulus facilitation (PStF) across forearm muscles match the pattern of postspike facilitation (PSpF)? Second, does the output of RM cell aggregates tested with StTA favor forearm extensor muscles, as reported for individual RM cells in the companion paper? Third, how do RM poststimulus effects compare with corticomotoneuronal (CM) poststimulus effects? 3. Microstimuli were applied at the sites of 37 RM cells, identified by SpTA of EMG activity in awake monkeys performing an alternating wrist movement task. 4. The magnitudes of PStF at 5, 10, and 20 microA were, respectively, 4.3, 10.1, and 13.7 times greater than PSpF of the same muscles, reflecting activation, by the stimulus, of multiple RM cells. RM cell PStF was weaker than CM PStF. 5. The onset latency of poststimulus suppression (PStS) exceeded that of PStF. For example, at 20 microA the difference was 2.6 ms, comparable with the difference between PSpF and postspike suppression (PSpS). 6. The patterns of poststimulus effects on forearm flexor and extensor muscles were categorized in the same manner as postspike effects. Three major patterns were observed: 1) pure facilitation, 2) reciprocal suppression, and 3) cofacilitation of extensors and flexors. 7. The profile of PStF across synergist muscles was broadly similar to that of PSpF. At 83% of sites, the muscle with the greatest PSpF was also the muscle with the greatest PStF. At 30% of sites (11 of 37), the set of muscles with PStF (muscle field) exactly matched the set with PSpF. Overall, the level of discrepancies in SpTAs versus StTAs computed at the same RM cell sites was 27%. Most of these discrepancies could be attributed to muscles with the weakest effects. 8. The fact that the poststimulus muscle fields at many RM cell sites matched the postspike fields at the same sites, even though the poststimulus effects were greater in magnitude and were mediated by more cells, suggests clustering of RM cells with similar target motoneuron pools.(ABSTRACT TRUNCATED AT 400 WORDS)

Contribution of Sensory Feedback to the Generation of Extensor Activity During Walking in the Decerebrate Cat

1999 ◽  
Vol 81 (2) ◽  
pp. 758-770 ◽  
Author(s):  
Gordon W. Hiebert ◽  
Keir G. Pearson
Keyword(s):  
Sensory Feedback ◽  
Knee Extensor ◽  
Afferent Feedback ◽  
Knee Extensors ◽  
Total Contribution ◽  
Decerebrate Cat ◽  
Dorsal Roots ◽  
Level Of Activity ◽  
Extensor Muscles ◽  
Decerebrate Cats

Contribution of sensory feedback to the generation of extensor activity during walking in the decerebrate cat. In this investigation we have estimated the afferent contribution to the generation of activity in the knee and ankle extensor muscles during walking in decerebrate cats by loading and unloading extensor muscles, and by unilateral deafferentation of a hind leg. The total contribution of afferent feedback to extensor burst generation was estimated by allowing one hind leg to step into a hole in the treadmill belt on which the animal was walking. In the absence of ground support the level of activity in knee and ankle extensor muscles was reduced to ∼70% of normal. Activity in the ankle extensors could be restored during the “foot-in-hole” trials by selectively resisting extension at the ankle. Thus feedback from proprioceptors in the ankle extensor muscles probably makes a large contribution to burst generation in these muscles during weight-bearing steps. Similarly, feedback from proprioceptors in knee extensor appears to contribute substantially to the activation of knee extensor muscles because unloading and loading these muscles, by lifting and dropping the hindquarters, strongly reduced and increased, respectively, the level of activity in the knee extensors. This conclusion was supported by the finding that partial deafferentation of one hind leg by transection of the L4–L6 dorsal roots reduced the level of activity in the knee extensors by ∼50%, but did not noticeably influence the activity in ankle extensor muscles. However, extending the deafferentation to include the L7–S2dorsal roots decreased the ankle extensor activity. We conclude that afferent feedback contributes to more than one-half of the input to knee and ankle extensor motoneurons during the stance phase of walking in decerebrate cats. The continuous contribution of afferent feedback to the generation of extensor activity could function to automatically adjust the intensity of activity to meet external demands.

scholarly journals Solid−liquid critical behavior of water in nanopores

2015 ◽  
Vol 112 (27) ◽  
pp. 8221-8226 ◽  
Author(s):  
Kenji Mochizuki ◽  
Kenichiro Koga
Keyword(s):  
Critical Points ◽  
Liquid Water ◽  
Phase Changes ◽  
Dynamics Simulation ◽  
Scaling Analysis ◽  
Widom Line ◽  
First Order ◽  
Low Dimensional ◽  
Solid Liquid ◽  
First Order Phase

Nanoconfined liquid water can transform into low-dimensional ices whose crystalline structures are dissimilar to any bulk ices and whose melting point may significantly rise with reducing the pore size, as revealed by computer simulation and confirmed by experiment. One of the intriguing, and as yet unresolved, questions concerns the observation that the liquid water may transform into a low-dimensional ice either via a first-order phase change or without any discontinuity in thermodynamic and dynamic properties, which suggests the existence of solid−liquid critical points in this class of nanoconfined systems. Here we explore the phase behavior of a model of water in carbon nanotubes in the temperature−pressure−diameter space by molecular dynamics simulation and provide unambiguous evidence to support solid−liquid critical phenomena of nanoconfined water. Solid−liquid first-order phase boundaries are determined by tracing spontaneous phase separation at various temperatures. All of the boundaries eventually cease to exist at the critical points and there appear loci of response function maxima, or the Widom lines, extending to the supercritical region. The finite-size scaling analysis of the density distribution supports the presence of both first-order and continuous phase changes between solid and liquid. At around the Widom line, there are microscopic domains of two phases, and continuous solid−liquid phase changes occur in such a way that the domains of one phase grow and those of the other evanesce as the thermodynamic state departs from the Widom line.

scholarly journals Cerebellum and Prematurity: A Complex Interplay Between Disruptive and Dysmaturational Events

2021 ◽  
Vol 15 ◽  
Author(s):  
Giulia Spoto ◽  
Greta Amore ◽  
Luigi Vetri ◽  
Giuseppe Quatrosi ◽  
Anna Cafeo ◽  
...  
Keyword(s):  
Preterm Birth ◽  
Early Intervention ◽  
Critical Period ◽  
Motor Coordination ◽  
Cerebellar Development ◽  
Third Trimester ◽  
Complex Interplay ◽  
The Third ◽  
Developing Cerebellum

The cerebellum plays a critical regulatory role in motor coordination, cognition, behavior, language, memory, and learning, hence overseeing a multiplicity of functions. Cerebellar development begins during early embryonic development, lasting until the first postnatal years. Particularly, the greatest increase of its volume occurs during the third trimester of pregnancy, which represents a critical period for cerebellar maturation. Preterm birth and all the related prenatal and perinatal contingencies may determine both dysmaturative and lesional events, potentially involving the developing cerebellum, and contributing to the constellation of the neuropsychiatric outcomes with several implications in setting-up clinical follow-up and early intervention.

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