Tonic and Phasic Discharge Patterns in Toe Flexor γ-Motoneurons During Locomotion in the Decerebrate Cat

2002 ◽  
Vol 87 (1) ◽  
pp. 286-294 ◽  
Author(s):  
P. R. Murphy
Keyword(s):  
Mechanical Action ◽  
Emg Activity ◽  
Flexor Hallucis Longus ◽  
Plantar Flexor ◽  
Step Cycle ◽  
Decerebrate Cat ◽  
Hindlimb Muscles ◽  
Discharge Patterns ◽  
Flexor Digitorum ◽  
Α Activity

To investigate the specificity of fusimotor (γ) drive during locomotion, γ-efferents were recorded from the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) nerves in a decerebrate cat preparation. These nerves innervate hindlimb muscles that differ in some aspects of their mechanical action. For both FHL and FDL two stereotyped patterns of γ activity were distinguished. Tonic units fired throughout the step cycle and had less modulation, but higher minimum rates, than phasic units, which were mainly recruited with ankle extensor [soleus (SOL)] electromyogram (EMG) activity. Differences in the relative timing of these patterns were apparent. In FHL the activity of phasic and most tonic neurons peaked after EMG onset. With FDL, tonic units generally reached maximum rate before, while phasic units peaked after, the beginning of EMG activity. During locomotion FHL and FDL α activity were rhythmically recruited with SOL. However, consistent with previous reports, FHL and FDL differed in their patterns of α activity. FHL was stereotyped while FDL was variable. Both FHL and FDL had activity related to ankle extensor EMG, but only FDL exhibited a peak around the end of this phase. No corresponding γ activity was observed in FDL. In conclusion, 1) FHL and FDL received tonic and phasic fusimotor drive; 2) there was no α/γ linkage for the late FDL α burst; 3) phasic γ-efferents in both muscles received similar inputs, linked to plantar flexor α activity; and 4) tonic γ-efferents differed, to the extent that they were modulated at all. The FHL units peaked with the plantar flexor alphas. The FDL neurons generally peaked before α activity even began.

Recurrent inhibition to and from motoneurons innervating the flexor digitorum and flexor hallucis longus muscles of the cat

1990 ◽  
Vol 63 (3) ◽  
pp. 395-403 ◽  
Author(s):  
T. M. Hamm
Keyword(s):  
Tibialis Anterior ◽  
Recurrent Inhibition ◽  
Medial Gastrocnemius ◽  
Flexor Hallucis Longus ◽  
Flexor Digitorum Longus ◽  
Lateral Gastrocnemius ◽  
Hindlimb Muscles ◽  
Inhibitory Postsynaptic Potentials ◽  
Flexor Digitorum ◽  
Stimulation Of

1. Recurrent inhibitory postsynaptic potentials (IPSPs) to and from motoneurons innervating the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) muscles of the cat were investigated to determine whether recurrent inhibitory projections involving these motoneurons are similar--as would be consistent with the Ia and anatomic synergism of FDL and FHL--or are dissimilar, as are the activities of these muscles during locomotion (O'Donovan et al. 1982). 2. Composite recurrent IPSPs were recorded in several species of motoneurons innervating hindlimb muscles in response to stimulation of a number of muscle nerves in cats allowed to become unanesthetized after ischemic decapitation. 3. No recurrent IPSPs from stimulation of the FDL nerve were observed in motoneurons innervating FDL, FHL, lateral gastrocnemius-soleus (LG-S), medial gastrocnemius (MG), plantaris (Pl), tibialis anterior (TA), or extensor digitorum longus (EDL). 4. The recurrent IPSPs produced by stimulation of FHL were larger and found more frequently in LG-S than in FDL motoneurons. Recurrent inhibition from FHL was also greater in Pl than in FDL motoneurons. 5. The recurrent IPSPs produced by stimulation of LG-S, PL, and MG were larger in FHL than in FDL motoneurons, and those from LG-S and MG were found more frequently in FHL than in FDL motoneurons. 6. Stimulation of the TA nerve produces recurrent IPSPs in FDL but not in FHL motoneurons. A few FDL and FHL cells (6 of 23 and 9 of 34, respectively) received small (less than 0.5 mV) recurrent IPSPs from stimulation of the EDL nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent collaterals of motoneurons projecting to distal muscles in the cat hindlimb

1992 ◽  
Vol 67 (5) ◽  
pp. 1359-1366 ◽  
Author(s):  
M. L. McCurdy ◽  
T. M. Hamm
Keyword(s):  
Recurrent Inhibition ◽  
Flexor Hallucis Longus ◽  
Flexor Digitorum Longus ◽  
First Order ◽  
Hindlimb Muscles ◽  
Ankle Muscles ◽  
Anterior Tibial ◽  
Recurrent Collateral ◽  
Recurrent Collaterals ◽  
Flexor Digitorum

1. Recurrent collaterals of motoneurons innervating muscles that have a role in control of the hindlimb digits were studied with neuroanatomic tracing methods to determine whether these motoneurons have simple recurrent collateral arbors in comparison with those of hip, knee, and ankle muscles. 2. Motoneurons innervating the hindlimb muscles plantaris (Pln), flexor hallucis longus (FHL), or flexor digitorum longus (FDL) were injected with 10% horseradish peroxidase. Recurrent collaterals were reconstructed from serial transverse sections. 3. No recurrent collaterals were observed in a sample of 10 FDL motoneurons. 4. FHL motoneurons had simple recurrent collateral arbors as assessed by number of first-order collaterals, number of collateral swellings, number of end branches, and the highest-order branch of individual collateral trees. Recurrent collateral arbors of Pln motoneurons were more complex than those of FHL motoneurons. Pln and FHL recurrent collateral arbors were less complex than those described for gastrocnemius-soleus, anterior tibial, and posterior biceps motoneurons. 5. These anatomic findings correspond well with electrophysiological results indicating that the recurrent inhibition produced by FHL motoneurons is weak and that FDL motoneurons do not produce recurrent inhibition. In addition, Pln motoneurons are reported to produce stronger recurrent inhibition than FHL motoneurons in many motor pools. 6. Consideration of these results with respect to the mechanical actions and patterns of motor activity observed in FDL, FHL, and Pln suggests that the complexity of recurrent collaterals of a motoneuron pool and the extent of its contribution to recurrent inhibition diminish with its involvement in the individualized control of the digits.

Cat hindlimb muscles exert substantial torques outside the sagittal plane

1993 ◽  
Vol 69 (1) ◽  
pp. 282-285 ◽  
Author(s):  
J. H. Lawrence ◽  
T. R. Nichols ◽  
A. W. English
Keyword(s):  
Sagittal Plane ◽  
Joint Stiffness ◽  
Tibialis Posterior ◽  
Flexor Hallucis Longus ◽  
Plantar Surface ◽  
Hindlimb Muscles ◽  
Force Moment ◽  
Orthogonal Components ◽  
Adult Cats ◽  
Flexor Digitorum

1. We studied the contributions of several hindlimb muscles to ankle torque in adult cats deeply anesthetized with pentobarbital sodium. Isometric torques were measured with a multiaxis, force-moment sensor connected to the plantar surface of the foot. 2. Individual muscle torques were provoked by using a combination of muscle nerve stimulation and selective denervations and tenotomies. Torques were represented by three orthogonal components; defined as dorsiflexion/plantarflexion, inversion/eversion (rotation about the long axis of the foot), and toe-in/toe-out (rotation about the axis of the tibia). 3. Most of the muscles tested exerted substantial torques about more than one of the orthogonal axes, each of which shared a common origin centered midway between the medial and lateral malleoli. The lateral and especially the medial head of the gastrocnemius muscle exhibited large toe-out torques and eversion torques as well as the classical plantarflexion components. 4. The torque exerted by tibialis anterior was seen to oppose that of both medial and lateral gastrocnemius in each of the three directions. The toe-in and inversion torques exerted by tibialis posterior was opposed in these directions by both peroneus brevis and peroneus longus. Flexor hallucis longus exerted approximately 10 times more plantarflexion torque than did flexor digitorum longus; therefore, these two muscles cannot be considered pure synergists. 5. The major plantarflexors and dorsiflexor of the cat ankle joint contribute substantial torques outside the sagittal plane. Their opposing torques lead to increased joint stiffness; the net effect of coactivation of these muscles causes ground reaction forces oriented so as to maintain stability during quadrupedal stance.

Modulation of ipsi- and contralateral reflex responses in unrestrained walking cats

1980 ◽  
Vol 44 (5) ◽  
pp. 1024-1037 ◽  
Author(s):  
J. Duysens ◽  
G. E. Loeb
Keyword(s):  
Emg Activity ◽  
Strict Sense ◽  
Skin Area ◽  
Step Cycle ◽  
Reflex Responses ◽  
Plantar Surface ◽  
Electrical Shocks ◽  
Excitatory Responses ◽  
Flexor Digitorum ◽  
Stimulation Of

1. The modulation of reflex responses in up to 10 simultaneously recorded hindlimb muscles was studied in unrestrained cats walking on a treadmill. Single electrical shocks of various strengths were applied to different skin areas of teh hindlimb at different times of the step cycle while the resulting EMG responses were sampled and analyzed. 2. Two excitatory response peaks (P1 and P2) at a latency of about 10 and 25 ms, respectively, were seen in all flexors examined (sartorius, semitendinosus, tibialis anterior, extensor digitorum longus). Stimulation of most skin areas was effective but responses were most easily obtained from stimuli applied to the foot or ankle. During the step cycle there was a marked modulation of the amplitudes of the responses, especially the P2 responses, which grew larger toward the end of stance when a maximum was reached, followed by a steady decline throughout swing. This pattern was very similar for various flexors, although these muscles differed considerably in their normal EMG activity pattern during walking. 3. Flexor responses were absent when the same stimuli were applied during the early stance phase. Instead, inhibition of the ongoing EMG activity was seen at a latency of 10 ms or less in all extensors examined (semimembranosus, quadriceps, soleus, gastrocnemius medialis, flexor digitorum longus). The inhibition was followed by a late excitatory peak (P3) at about 35-ms latency in all extensors except soleus. 4. Certain stimulation sites yielded exceptions to the above patterns. Stimulation of the skin area innervated by the sural nerve yielded larger and earlier MG excitatory responses as compared to stimulation of other skin areas. Activation of the plantar surface of the foot often failed to elicit P2 responses in the hip flexor sartorius, which showed inhibition instead. 5. In the hindlimb contralateral to the stimulus, excitatory responses occurred both in flexors and extensors at a latency of 20-25 ms. The pattern of modulation of these responses was similar to the ipsilateral modulation of P2 flexor and P3 extensor responses. Soleus failed to show a crossed response. 6. The data indicate that flexor and extensor responses differ both with respect to their latency and to their correlation with the ongoing EMG reactivity. It is concluded that these stimuli do not demonstrate reflex reversal in the strict sense in the normal walking cat but that there is modulation of transmission in a flexor excitatory and extensor inhibitory pathway, possibly by the flexor part of the spinal locomotor oscillator. In addition, there are some specialized flexor inhibitory and extensor excitatory pathways. The slow soleus muscle does not seem to be excited through these pathways.

Cat hindlimb motoneurons during locomotion. III. Functional segregation in sartorius

1987 ◽  
Vol 57 (2) ◽  
pp. 554-562 ◽  
Author(s):  
J. A. Hoffer ◽  
G. E. Loeb ◽  
N. Sugano ◽  
W. B. Marks ◽  
M. J. O'Donovan ◽  
...  
Keyword(s):  
Stance Phase ◽  
Swing Phase ◽  
Emg Activity ◽  
Sartorius Muscle ◽  
Electromyographic Activity ◽  
Step Cycle ◽  
Implanted Electrodes ◽  
Spike Triggered Averaging ◽  
Single Burst ◽  
Discharge Patterns

Cat sartorius has two distinct anatomical portions, anterior (SA-a) and medial (SA-m). SA-a acts to extend the knee and also to flex the hip. SA-m acts to flex both the knee and the hip. The objective of this study was to investigate how a "single motoneuron pool" is used to control at least three separate functions mediated by the two anatomical portions of one muscle. Discharge patterns of single motoneurons projecting to the sartorius muscle were recorded using floating microelectrodes implanted in the L5 ventral root of cats. The electromyographic activity generated by the anterior and medial portions of sartorius was recorded with chronically implanted electrodes. The muscle portion innervated by each motoneuron was determined by spike-triggered averaging of the EMGs during walking on a motorized treadmill. During normal locomotion, SA-a exhibited two bursts of EMG activity per step cycle, one during the stance phase and one during the late swing phase. In contrast, every recorded motoneuron projecting to SA-a discharged a single burst of action potentials per step cycle. Some SA-a motoneurons discharged only during the stance phase, whereas other motoneurons discharged only during the late swing phase. In all cases, the instantaneous frequencygram of the motoneuron was well fit by the rectified smoothed EMG envelope generated by SA-a during the appropriate phase of the step cycle. During normal locomotion, SA-m exhibited a single burst of EMG activity per step cycle, during the swing phase. The temporal characteristics of the EMG bursts recorded from SA-m differed from the swing-phase EMG bursts generated by SA-a.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive Value of Manual Muscle Testing and Gait Analysis in Normal Ankles by Dynamic Electromyography

Foot & Ankle ◽  
1986 ◽  
Vol 6 (5) ◽  
pp. 254-259 ◽  
Author(s):  
Jacquelin Perry ◽  
Mary Lloyd Ireland ◽  
Jo Gronley ◽  
M. Mark Hoffer
Keyword(s):  
Normal Subjects ◽  
Manual Muscle Testing ◽  
Emg Activity ◽  
Flexor Hallucis Longus ◽  
Muscle Action ◽  
Manual Muscle Test ◽  
Poor Grade ◽  
Muscle Testing ◽  
Grade 3 ◽  
Flexor Digitorum

Eight muscles about the ankle of seven normal subjects were assessed by electromyography (EMG) during manual muscle testing (MMT) and walking. Three strength levels (normal, fair, trace) and three gait velocities (free, fast, slow) were tested. The muscles studied included the gastrocnemius, soleus, posterior tibialis, flexor digitorum longus, flexor hallucis longus, anterior tibialis, extensor digitorum longus, and extensor hallucis longus. Relative intensity of muscle action was quantitated visually (using an eight-point scale based on amplitude and density of the signal). The data showed that EMG activity increased directly as more muscle force was required during the different manual muscle test levels and increased walking speeds. No MMT isolated activity to the specific muscle thought being tested. Instead, there always was a synergistic response. Both the gastrocnemius and soleus contributed significantly to plantarflexion regardless of knee position. The intensity of muscle action during walking related to the manual muscle test grades. Walking at the normal free velocity (meters/min) required fair (grade 3) muscle action. During slow gait the muscle functioned at a poor (grade 2) level. Fast walking necessitated muscle action midway between fair and normal, which was interpreted as good (grade 4).

scholarly journals Lower leg muscle structure and function are altered in long-distance runners with medial tibial stress syndrome: a case control study

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Joshua Mattock ◽  
Julie R. Steele ◽  
Karen J. Mickle
Keyword(s):  
Lower Leg ◽  
Structure And Function ◽  
Flexor Hallucis Longus ◽  
Plantar Flexor ◽  
Distance Runners ◽  
Long Distance ◽  
Cross Sectional ◽  
Muscle Structure ◽  
Leg Muscle ◽  
And Function

Abstract Background Medial tibial stress syndrome (MTSS) is a common lower leg injury experienced by runners. Although numerous risk factors are reported in the literature, many are non-modifiable and management of the injury remains difficult. Lower leg muscle structure and function are modifiable characteristics that influence tibial loading during foot-ground contact. Therefore, this study aimed to determine whether long-distance runners with MTSS displayed differences in in vivo lower leg muscle structure and function than matched asymptomatic runners. Methods Lower leg structure was assessed using ultrasound and a measure of lower leg circumference to quantify muscle cross-sectional area, thickness and lean lower leg girth. Lower leg function was assessed using a hand-held dynamometer to quantify maximal voluntary isometric contraction strength and a single leg heel raise protocol was used to measure ankle plantar flexor endurance. Outcome variables were compared between the limbs of long-distance runners suffering MTSS (n = 20) and matched asymptomatic controls (n = 20). Means, standard deviations, 95 % confidence intervals, mean differences and Cohen’s d values were calculated for each variable for the MTSS symptomatic and control limbs. Results MTSS symptomatic limbs displayed a significantly smaller flexor hallucis longus cross-sectional area, a smaller soleus thickness but a larger lateral gastrocnemius thickness than the control limbs. However, there was no statistical difference in lean lower leg girth. Compared to the matched control limbs, MTSS symptomatic limbs displayed deficits in maximal voluntary isometric contraction strength of the flexor hallucis longus, soleus, tibialis anterior and peroneal muscles, and reduced ankle plantar flexor endurance capacity. Conclusions Differences in lower leg muscle structure and function likely render MTSS symptomatic individuals less able to withstand the negative tibial bending moment generated during midstance, potentially contributing to the development of MTSS. The clinical implications of these findings suggest that rehabilitation protocols for MTSS symptomatic individuals should aim to improve strength of the flexor hallucis longus, soleus, tibialis anterior and peroneal muscles along with ankle plantar flexor endurance. However, the cross-sectional study design prevents us determining whether between group differences were a cause or effect of MTSS. Therefore, future prospective studies are required to substantiate the study findings.

Accessory museulus soleus

1926 ◽  
Vol 22 (5-6) ◽  
pp. 511-513
Author(s):  
V. N. Ternovsky ◽  
M. Sadykova
Keyword(s):  
Lower Limb ◽  
Lower Leg ◽  
Flexor Hallucis Longus ◽  
Posterior Surface ◽  
Flexor Digitorum Longus ◽  
Accessory Muscle ◽  
Peroneus Brevis ◽  
The Right ◽  
Flexor Digitorum

Dissecting the muscles of the right lower limb of an unknown corpse, we found an accessory muscle on the posterior surface of the lower leg. This muscle (see Fig.) Was bordered behind in. soleus and with the tendon m. plantaris, in front - with in. flexor hallucis longus, medially - c m. flexor digitorum longus and laterally - c m. peroneus brevis.

scholarly journals Geniohyoid muscle function in awake canines

2003 ◽  
Vol 95 (2) ◽  
pp. 810-817 ◽  
Author(s):  
M. Yokoba ◽  
H. G. Hawes ◽  
P. A. Easton
Keyword(s):  
Muscle Function ◽  
Breathing Pattern ◽  
Muscle Length ◽  
Upper Airway ◽  
Mechanical Action ◽  
Emg Activity ◽  
Airway Occlusion ◽  
Lateral Decubitus ◽  
The Right ◽  
Emg Electrodes

The geniohyoid (Genio) upper airway muscle shows phasic, inspiratory electrical activity in awake humans but no activity and lengthening in anesthetized cats. There is no information about the mechanical action of the Genio, including length and shortening, in any awake, nonanesthetized mammal during respiration (or swallowing). Therefore, we studied four canines, mean weight 28.8 kg, 1.5 days after Genio implantation with sonomicrometry transducers and bipolar electromyogram (EMG) electrodes. Awake recordings of breathing pattern, muscle length and shortening, and EMG activity were made with the animal in the right lateral decubitus position during quiet resting, CO2-stimulated breathing, inspiratory-resisted breathing (80 cmH2O · l-1 · s), and airway occlusion. Genio length and activity were also measured during swallowing, when it shortened, showing a 9.31% change from resting length, and its EMG activity increased 6.44 V. During resting breathing, there was no phasic Genio EMG activity at all, and Genio showed virtually no movement during inspiration. During CO2-stimulated breathing, Genio showed minimal lengthening of only 0.07% change from resting length, whereas phasic EMG activity was still absent. During inspiratory-resisted breathing and airway occlusion, Genio showed phasic EMG activity but still lengthened. We conclude that the Genio in awake, nonanesthetized canines shows active contraction and EMG activity only during swallowing. During quiet or stimulated breathing, Genio is electrically inactive with passive lengthening. Even against resistance, Genio is electrically active but still lengthens during inspiration.

scholarly journals Transspinal stimulation decreases corticospinal excitability and alters the function of spinal locomotor networks

2019 ◽  
Vol 122 (6) ◽  
pp. 2331-2343 ◽  
Author(s):  
Timothy S. Pulverenti ◽  
Md. Anamul Islam ◽  
Ola Alsalman ◽  
Lynda M. Murray ◽  
Noam Y. Harel ◽  
...  
Keyword(s):  
Evoked Potentials ◽  
Motor Evoked Potentials ◽  
Silent Period ◽  
Surface Emg ◽  
Corticospinal Excitability ◽  
Emg Activity ◽  
Step Cycle ◽  
Healthy Humans ◽  
Descending Volleys ◽  
Period Duration

Locomotion requires the continuous integration of descending motor commands and sensory inputs from the legs by spinal central pattern generator circuits. Modulation of spinal neural circuits by transspinal stimulation is well documented, but how transspinal stimulation affects corticospinal excitability during walking in humans remains elusive. We measured the motor evoked potentials (MEPs) at multiple phases of the step cycle conditioned with transspinal stimulation delivered at sub- and suprathreshold intensities of the spinally mediated transspinal evoked potential (TEP). Transspinal stimulation was delivered before or after transcranial magnetic stimulation during which summation between MEP and TEP responses in the surface EMG was absent or present. Relationships between MEP amplitude and background EMG activity, silent period duration, and phase-dependent EMG amplitude modulation during and after stimulation were also determined. Ankle flexor and extensor MEPs were depressed by suprathreshold transspinal stimulation when descending volleys were timed to interact with transspinal stimulation-induced motoneuron depolarization at the spinal cord. MEP depression coincided with decreased MEP gain, unaltered MEP threshold, and unaltered silent period duration. Locomotor EMG activity of bilateral knee and ankle muscles was significantly depressed during the step at which transspinal stimulation was delivered but fully recovered at the subsequent step. The results support a model in which MEP depression by transspinal stimulation occurs via subcortical or spinal mechanisms. Transspinal stimulation disrupts the locomotor output of flexor and extensor motoneurons initially, but the intact nervous system has the ability to rapidly overcome this pronounced locomotor adaptation. In conclusion, transspinal stimulation directly affects spinal locomotor centers in healthy humans. NEW & NOTEWORTHY Lumbar transspinal stimulation decreases ankle flexor and extensor motor evoked potentials (MEPs) during walking. The MEP depression coincides with decreased MEP gain, unaltered MEP threshold changes, and unaltered silent period duration. These findings indicate that MEP depression is subcortical or spinal in origin. Healthy subjects could rapidly overcome the pronounced depression of muscle activity during the step at which transspinal stimulation was delivered. Thus, transspinal stimulation directly affects the function of spinal locomotor networks in healthy humans.

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