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S Rossignol

Publications and source records attributed to S Rossignol.

At least 73 records · Page 4Linked to original sources
PubMed1988

Rhythmic fluctuations of dorsal root potentials and antidromic discharges of primary afferents during fictive locomotion in the cat.

1. This study examines rhythmical activity of primary afferents occurring during "fictive" locomotion in decorticate paralyzed cats. Oscillations of the dorsal root potential (DRP) at the frequency of the locomotor rhythm have been observed at the lumbosacral and cervical levels. In addition, rhythmic antidromic discharges of primary afferent units have been recorded from the proximal stumps of cut dorsal root filaments. A detailed study of the relationships between the DRP fluctuations, the antidromic discharges, and the locomotor activity monitored by recording extensor and flexor muscle nerves is presented. 2. Typical DRP recordings from both lumbosacral and cervical levels show two negative waves (N1 and N2) separated by positive troughs (P1 and P2) in each locomotor cycle. Linear regression analyses indicate that the first negative wave (which generally has the largest amplitude) is related to the flexor activity whereas the second is related to the extensor activity. The relative amplitude of the two negative waves may vary without apparent concomitant changes in the recorded flexor or extensor motor nerves. The positive troughs occur respectively close to the period of transition between flexor and extensor activities and between extensor and flexor activities. 3. DRPs of similar period and amplitude can be observed in different ipsilateral roots recorded simultaneously. The DRPs recorded bilaterally from the same segment have the same periodicity but are out-of-phase. Point-to-point variations of amplitude in bilaterally recorded roots are not correlated. This suggests that the polarization of primary afferents on one side is mainly related to the locomotor events on that side. DRPs have been recorded in cats spinalized at Th13 and injected with nialamide and l-DOPA. This suggests that although the supraspinal contribution may be important, at least part of the DRPs may result from locomotor activity within the spinal cord itself. 4. A salient finding in our experiments was that of rhythmic antidromic unit discharges in the proximal stump of cut dorsal root filaments. Of the 194 units recorded, 19% (37/194) discharged in distinct bursts occurring at fixed times in the locomotor cycle. The majority of the units discharged either one burst during the period of flexor or extensor activity or one burst during one of the two periods of transition. Three units discharged two bursts per locomotor cycle. The frequency of the antidromic discharges of some units in one limb were also found to be modulated by stimulation of the skin or passive manipulation of the limbs.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1988

Spinal locomotion: a comparison of the kinematics and the electromyographic activity in the same animal before and after spinalization.

To assess the recuperation of locomotor functions of the hindlimbs after spinal section at T13, EMGs and kinematics were analyzed in a chronically implanted adult cat before and up to 14 days after spinalization. At this time, the cat was capable of coordinated walking, plantar foot contact and weight support of the hindquarters for several step cycles. There was however a foot drag early in swing and the steps tended to be shorter. Most muscles showed similar timing characteristics although there were some changes in amplitude. It is concluded that the spinal cord can generate a detailed locomotor pattern in the hindlimbs even in the adult animal.

Anesthesia↗
PubMed1987

The effects of clonidine and yohimbine on locomotion and cutaneous reflexes in the adult chronic spinal cat.

The effects on the locomotor pattern of a noradrenergic agonist (clonidine) and an antagonist (yohimbine) were studied in 3 adult chronic spinal cats walking on a treadmill. In the early post-transection period, when the cat walked mainly on the tip of its feet, without supporting its own weight, it was observed that clonidine (150 micrograms/kg) could induce a good bilateral foot placement and intermittent complete weight support. When clonidine was given 1-3 months following the transection, at a time when the spinal cats had a stable and regular locomotor performance, the step length increased markedly, especially at low speeds. This was associated with an increase in the duration of the flexor and extensor bursts, as well as an increase of the angular excursion of all joints. These effects, seen during forward locomotion, were also observed during backward locomotion. In addition, the latter was more easily elicited after clonidine. Yohimbine (1.5-3 mg/kg) partially antagonized these effects. The threshold current needed to elicit a small flexion reflex through wires implanted in the dorsum of the paw was 2-3 times higher after clonidine. Trains of shocks in the animal, standing quietly, did not induce the prolonged late discharges normally found in acute spinal cats. Fast paw shaking, elicited by dipping one paw in water, was abolished by clonidine and reappeared after yohimbine. These results indicate that noradrenergic drugs may influence both spinal locomotion and the excitability of cutaneous reflexes. This class of substances could thus play a useful role in the recovery and/or maintenance of locomotor functions after spinal trauma.

Animals↗
PubMed1987

Recovery of locomotion after chronic spinalization in the adult cat.

Cats were spinalized (T13) as adults and were trained to walk with the hindlimbs on a treadmill. After 3 weeks to 3 months and up to 1 year depending on the animal, all were capable of walking on the plantar surface of the feet and support the weight of the hindquarters. Interactive training appeared to accelerate the recovery of locomotion and maintain smooth locomotor movements. Despite the obvious loss of voluntary control and equilibrium which the experimenter partially compensated for by maintaining the thorax and/or the tail, the cats could walk with a regular rhythm and a well-coordinated hindlimb alternation at speeds of 0.1-1.2 m/s. Cycle duration as well as stance and swing duration resembled those of normal cats at comparable speeds. The range of angular motion was also similar to that observed in intact cats as was the coupling between different joints. The EMG activity of the hindlimb and lumbar axial muscles also retained the characteristics observed in the intact animal. Some deficits such as a dragging of the foot in early swing and diminution of the angular excursion in the knee were seen at later stages. Thus, the adult spinal cat preparation is considered as a useful model to study the influence of different types of training and of different drugs or other treatments in the process of locomotor recovery after injury to the spinal cord.

Adaptation, Physiological↗
PubMed1987

Locomotor deficits in the mutant mouse, Lurcher.

The effect of total Purkinje cell degeneration on treadmill locomotion was studied in the cerebellar mutant mouse Lurcher. Other movements such as swimming and scratching were also studied in order to evaluate the cerebellar control of rhythmic actions. Cinematographic and electromyographic recordings were taken from normal and Lurcher mice that were subsequently perfused to obtain a Purkinje cell count. Walking deteriorated progressively and was clearly abnormal in 30 day old Lurchers with 90% Purkinje cell degeneration. In adult Lurcher mice in which Purkinje cells were totally absent, walking was characterized by short steps with exaggerated hindlimb flexion in the swing phase. Also, both the interlimb step ratio, defined as the step length of the reference limb divided by the step length of the opposite limb, and the interlimb coupling, defined as the temporal relation of one footfall with respect to the footfall of another limb, varied more than in normal mice. Furthermore, the locomotion of Lurcher mice displayed increased vertical displacement of the hip and an inability to produce continuous step cycles without stumbling. Both the EMG onset relative to foot contact and the EMG burst duration were highly variable, and a greater overlap in the activities of antagonist muscles at the transition from ankle extension to flexion was evident. Although both walking and swimming involve cyclical limb movements, the disorganization of the cycle and the irregular EMG pattern seen in the Lurcher during walking were not observed during swimming. Furthermore, scratching was well executed in the Lurcher mice. However, a consistently higher tonic extensor activity at the ankle appeared during walking, swimming and scratching. These results suggest that, in contrast to swimming and scratching, the requirements of walking depend to a greater degree on a functional cerebellar cortex for successful performance.

Age Factors↗
PubMed1987

A kinematic and electromyographic study of cutaneous reflexes evoked from the forelimb of unrestrained walking cats.

A kinematic and electromyographic (EMG) analysis was undertaken of the responses evoked in the forelimb of the cat by either mechanical obstruction of the forelimb during the swing phase of locomotion or by electrical stimulation of low-threshold cutaneous afferents during both swing and stance. Mechanical obstruction of the forelimb with a stiff metal rod evoked a complex response that allowed the cat to smoothly negotiate the obstacle without undue disruption of the overall locomotor rhythm. The initial movements were a flexion of the shoulder, together with a locking of the elbow joint, and a dorsiflexion of the wrist, which caused the limb to withdraw from the obstacle. They were followed by an extension of the shoulder, a flexion of the elbow, and a ventroflexion of the wrist, which together brought the limb forward and above the obstacle. The associated and complex pattern of short- and long-latency EMG responses was shown to be related to different aspects of the movement. At the shoulder there was a strong activation of flexor muscles; these responses were of long duration (greater than or equal to 100 ms) and generally lasted throughout the period of shoulder flexion. At the elbow, both flexor and extensor muscles were activated at short latency (9-13 ms). In flexors, this was followed by a cessation and subsequently an augmentation and prolongation of their activity. Dorsiflexors of both the wrist and digits were activated at short latency (10-12 ms) and remained active throughout the period of dorsiflexion of these joints. An injection of a local anesthetic into the area of skin contacted by the metal rod reduced or abolished all of the reflex responses, which suggests that the integrity of cutaneous reflex pathways is essential for the elaboration of these responses. Electrical stimulation of a cutaneous nerve innervating the distal forelimb (the superficial radial nerve) resulted in qualitatively similar, although weaker, responses to those obtained with the mechanical stimulation. Terminal experiments confirmed that these responses were mediated by low-threshold cutaneous afferents. Electrical stimulation also evoked short-latency excitatory responses (10-12 ms) in extensor muscles of the elbow. Generally, the largest reflex effects were obtained during the period of swing for flexor, extensor, and bifunctional muscles. During stance the stimulus was normally ineffective in exciting flexor muscles and in extensors evoked a short-latency inhibition, which was frequently followed by an increase in activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

The effects of 4-aminopyridine on the spinal cord: rhythmic discharges recorded from the peripheral nerves.

The effects of an intravenous injection (20 mg/kg) of 4-aminopyridine (4-AP) were initially investigated in acute low spinal cats (Th 13), in which L-DOPA had induced fictive locomotion after paralysis. 4-AP first accelerated the locomotor rhythm and could also change markedly the pattern of activation of some muscle nerves. Shortly after, the locomotor activity was replaced by synchronous rhythmic discharges (2.5-8.5 Hz) in flexor and extensor muscle nerves of the same limb girdle. Similar rhythmic activity was recorded after 4-AP alone (5-20 mg/kg) in the acute decerebrate spinal cat. Whilst the mean rate of the rhythmic activity could differ in the two limb girdles, discharges generated in one girdle appeared to be strongly influenced by those generated in the other. After a complete section of the spinal cord (Th13), the activity persisted in both the rostral and caudal segments although the interactions between the two disappeared. The persistence of the rhythmic activity caudal to the section underscores its spinal origin. In the chronic spinal rat, such rhythmic activity could still be induced in the lumbo-sacral cord despite degeneration of descending pathways. It appears that large doses of 4-AP exert potent effects on the spinal cord which can override other patterns of activity and synchronize the electrical activity of many neuronal elements.

4-Aminopyridine↗
PubMed1986

Discharge patterns of reticulospinal and other reticular neurons in chronic, unrestrained cats walking on a treadmill.

Recordings were made from single units in the medullary reticular formation (MRF) between AP-4.2 and AP-12.9 and from the midline to 3.7 mm lateral in chronically prepared, unrestrained cats walking on a treadmill. Recordings were made with rigid microelectrodes held in a microdrive, and reticulospinal neurons were identified by antidromic stimulation of their axons through microwires chronically implanted into the spinal cord at the L2 level. Electromyograms (EMGs) were recorded from flexor and extensor muscles of the fore- and hindlimbs as well as from back and neck muscles. In total, 295 cells were recorded from 40 penetrations in 4 cats; 252 of these cells were recorded from the more medial regions of the reticular formation encompassing the gigantocellular, magnocellular, and lateral tegmental fields; 38.5% of these (97/252) were antidromically identified from the spinal cord. The remaining 43 neurons (43/295) were recorded from a more lateral and ventral position. These medial and ventrolateral groups of neurons differed not only in position but also in aspects of their discharge during locomotion. Rank-ordered raster displays, triggered from the onset of each recorded muscle, were used to correlate neuronal and muscular activity. The discharge rate of 31% of the reticulospinal neurons (30/97) was modulated once or twice in each step cycle and was strictly related to one or more of the recorded EMGs (EMG-related neurons) on the basis of the pattern of discharge. The discharge of 33/97 (34%) of the neurons was modulated at the periodicity of the locomotor rhythm but could not be correlated with any of the recorded EMGs (locomotor-related cells), whereas the remaining 34/97 neurons (35%) were either silent, fired tonically, or were not related to the locomotor pattern (unrelated cells). Of the EMG-related neurons 27% were related to flexor muscles and the remaining 63% to extensor muscle activity. The discharge pattern of all except two of the flexor-related neurons was correlated with hindlimb muscle activity, whereas that of the extensor-related neurons was correlated almost equally with fore- and hindlimb muscles. Correlations were found with muscles lying both ipsilaterally and contralaterally to the site of the recordings. Although the locomotor-related neurons showed no preferential relation with any of the recorded EMGs, a comparison of the depth of modulation of their discharge measured from postevent histograms suggested that more of these cells were related to the forelimb than to the hindlimb.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Rhythmic antidromic discharges of single primary afferents recorded in cut dorsal root filaments during locomotion in the cat.

Single units recorded in the proximal stump of cut dorsal root filaments were found to antidromically discharge rhythmically during fictive locomotion in decorticate and paralyzed cats. Some units fired throughout the period of flexor or extensor nerve activity, whereas other units discharged near the transitional phases. Similar findings were made in acutely spinalized and paralyzed cats injected with L-DOPA, as well as in non-paralyzed decorticate cats walking on a treadmill. These results suggest that different types of primary afferents may be depolarized cyclically at different specific time in the step cycle by the central pattern generator for locomotion, and that this central control of the primary afferents may be involved in the modulation of the reflex transmission observed during locomotion.

Animals↗
PubMed1985

Forelimb responses to cutaneous nerve stimulation during locomotion in intact cats.

The reflex responses of forelimb muscles to electrical stimulation of the cutaneous superficial radial nerve were recorded during treadmill locomotion in chronically implanted cats. In brachialis and cleidobrachialis (muscles which are active mainly during the swing phase) the responses were maximal during the swing phase and minimal or absent during the stance phase. In the long head of triceps which is active mainly during the stance phase, responses were also minimal during stance and maximal during swing. It is concluded that, for some muscles, the period of maximal reflex responsiveness can be out of phase with the period of the step cycle during which they are normally active.

Animals↗
PubMed1984

Electromyographic study of lumbar back muscles during locomotion in acute high decerebrate and in low spinal cats.

The electromyographic (EMG) activity of the lumbar back muscles (multifidus, longissimus and iliocostalis) was investigated during treadmill locomotion in acute high decerebrate and in low spinal cats. During alternate stepping (0.7-2.0 m X s-1) in high decerebrate cats, the back muscles have two bursts of activity per step cycle. On the average these EMG bursts last about 170 ms and start some 25 ms before the onset of each vastus lateralis (VL). The two bursts in any one back muscle may have a different duration, the shortest burst on one side coinciding with the longest burst of the homologous contralateral muscle. There is often an overall asymmetry in the discharge wherein the bursts of activity in both ipsi- and contralateral muscles are longer at the onset of one of the VLs. Correlation analyses of several timing parameters of the bursts as a function of walking speeds were made. Different patterns of correlation were identified and it was found that, in most cases, the end of the bursts (with respect to the onset of VL activity) was best correlated with the speed of walking. During gallop, the back muscles activity is a single burst of about 200 ms duration which starts some 75 ms before the onset of VL. In low spinal cats walking after an injection of clonidine, the double burst pattern of EMG activation may be present if there is adequate weight support. However, when the animal steps with the hindlimbs extended and with insufficient weight support, these muscles have a tonic activity uncorrelated with the rhythmic activity of hindlimb muscles.

Animals↗
PubMed1984

Phase-dependent responses evoked in limb muscles by stimulation of medullary reticular formation during locomotion in thalamic cats.

Electromyographic and kinematic responses of all four limbs were studied when loci within the medullary reticular formation (MRF) were stimulated (30-ms train of 0.2-ms pulses at 300 Hz, strength 35 microA) during treadmill locomotion in spontaneously walking thalamic cats. Responses could be evoked in flexor or extensor muscles of any given limb by such stimulation, depending on the time during the step cycle at which the stimulus was delivered. Stimulation normally excited flexor muscles but could either excite or inhibit extensor muscles depending on the exact position of the electrode. Excitatory responses in extensor muscles were often followed by a short period of inhibition of activity. The responses in muscles of the opposing limbs of the same girdle were, in general, reciprocally organized. For instance, a stimulus delivered during the swing phase of the ipsilateral limb normally evoked excitatory responses both in flexor muscles of that limb and in extensor muscles of the contralateral limb. The same stimulus delivered during the stance phase of the ipsilateral limb evoked excitatory responses in ipsilateral extensor muscles and in contralateral flexor muscles. Responses were also observed at the same time in fore- and hindlimbs that were well organized with respect to the locomotor cycle. Seventy-five percent of all responses occurred within 8-20 ms of the onset of the stimulus train. Responses evoked in muscles of the opposing limbs of one girdle (e.g., a flexor of one limb and an extensor of the other) had similar latencies, suggesting that the responses were synchronously organized on both sides of the body rather than one being a consequence of the other. Although the majority of responses in a given muscle were elicited during its period of activity, responses could occasionally be evoked when there was no activity in that muscle or could be absent despite activity in the muscle. The short trains of stimuli were normally potent enough to affect the limb trajectory, which reflected changes in the onset or the offset of the activity of most muscles. Thus the stimuli effectively changed both the duration of the period of activity in these muscles and the overall step cycle. Longer trains of stimuli (200 ms) markedly amplified these changes to the point of completely resetting the locomotor rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

A study of jaw reflexes of the awake cat during mastication and locomotion.

This paper reports on experiments on the jaw opening reflex carried out while awake unrestrained cats were eating or walking on a treadmill. It is shown that the jaw opening reflex response to low intensity stimulation diminished in all phases of the masticatory cycle. The response to higher threshold afferents, however, is phase modulated so that the largest responses occur during the jaw closing phase. This is in accord with the need for increased protection of the soft tissues in this phase of the movement. In contrast, the digastric reflex amplitude does not change when the cat passes from quiet standing to walking on the treadmill. Evidence is presented that the electromyographic activity of the jaw closing muscles increases during upwards movement of the head during walking and decreases as the head falls. These data support the hypothesis that the myotatic reflex in the elevator muscles plays a role in stabilizing the mandible during locomotion.

Afferent Pathways↗
PubMed1981

Contralateral hindlimb responses to cutaneous stimulation during locomotion in high decerebrate cats.

High intensity stimuli of the skin were delivered to one hindlimb in various parts of the step cycle of decerebrate cats walking on a treadmill. Whereas the stimulated limb always flexes after the stimulation there is, in the contralateral limb, a crossed flexion response during swing or a crossed extension response during stance. The frequency distribution of the responses in contralateral flexor or extensor muscles peaks at around the onset of the respective locomotor bursts although responses can be evoked before and after that onset. In certain periods of the cycle, largely corresponding to the transition from flexor or extensor activity and vice versa, the responses can occur in either muscles. The long latencies of crossed responses are similar to that of the ipsilateral responses so that both occur approximately at the same time. The amplitude and duration of crossed responses vary according to the phase of the walking cycle. The types of responses and the overall changes in the step cycles suggest that crossed extension responses mainly serve to sustain the increased weight to the contralateral side during ipsilateral flexion whereas crossed flexion responses appear well studied to rapidly rephase the contralateral limb step cycle to that of the ipsilateral limb which is markedly perturbed by the flexion response elicited during its stance phase.

Animals↗