Effect of myofeedback on the threshold of the stretch reflex response of post-stroke spastic patients.

Purpose We propose a visual myofeedback protocol as a coadjuvant therapy to standard rehabilitation of post-stroke spastic patients. We also argue in favor of the tonic stretch reflex threshold (TSRT) as a more sensitive unit for quantifying subtle changes in the spastic response that may be induced by biofeedback training. Method Sixteen volunteers with ischaemic stroke were divided into an experimental group (EG), subjected to myofeedback training in parallel with conventional physical therapy and a control group (CG), receiving only conventional physical therapy. The EG subjects underwent a six-week myofeedback training, with two sessions weekly. Both groups followed the same treatment schedule for physical therapy. The TSRTs of the volunteers' spastic muscles were assessed before the beginning of the experimental protocol and 3 weeks after it ended. Results Both groups showed some degree of improvement in the level of spasticity when the final TSRT values were compared to the initial values. However, the percentage of improvement (after-before) of the experimental group (38.59%) was significantly higher than that in the control group (18.58%). Conclusion The myofeedback training provided a significant contribution to conventional treatment, allowing for a better improvement of the spastic condition. Implications for rehabilitation Biofeedback is an effective means of improving motor control of post-stroke spastic patients. The Tonic Stretch Reflex Threshold is a more sensitive quantitative measure to assess upper-limb post-stroke spasticity. Spastic patients who participate in myofeedback training along with physical therapy can improve faster then those who participate only in traditional physical therapy rehabilitation protocols.

Spike Timing-Dependent Plasticity in the Long-Latency Stretch Reflex Following Paired Stimulation from a Wearable Electronic Device.

The long-latency stretch reflex (LLSR) in human elbow muscles probably depends on multiple pathways; one possible contributor is the reticulospinal tract. Here we attempted to induce plastic changes in the LLSR by pairing noninvasive stimuli that are known to activate reticulospinal pathways, at timings predicted to cause spike timing-dependent plasticity in the brainstem. In healthy human subjects, reflex responses in flexor muscles were recorded following extension perturbations at the elbow. Subjects were then fitted with a portable device that delivered auditory click stimuli through an earpiece, and electrical stimuli around motor threshold to the biceps muscle via surface electrodes. We tested the following four paradigms: biceps stimulus 10 ms before click (Bi-10ms-C); click 25 ms before biceps (C-25ms-Bi); click alone (C only); and biceps alone (Bi only). The average stimulus rate was 0.67 Hz. Subjects left the laboratory wearing the device and performed normal daily activities. Approximately 7 h later, they returned, and stretch reflexes were remeasured. The LLSR was significantly enhanced in the biceps muscle (on average by 49%) after the Bi-10ms-C paradigm, but was suppressed for C-25ms-Bi (by 31%); it was unchanged for Bi only and C only. No paradigm induced LLSR changes in the unstimulated brachioradialis muscle. Although we cannot exclude contributions from spinal or cortical pathways, our results are consistent with spike timing-dependent plasticity in reticulospinal circuits, specific to the stimulated muscle. This is the first demonstration that the LLSR can be modified via paired-pulse methods, and may open up new possibilities in motor systems neuroscience and rehabilitation. SIGNIFICANCE STATEMENT: This report is the first demonstration that the long-latency stretch reflex can be modified by repeated, precisely timed pairing of stimuli known to activate brainstem pathways. Furthermore, pairing was achieved with a portable electronic device capable of delivering many more stimulus repetitions than conventional laboratory studies. Our findings open up new possibilities for basic research into these underinvestigated pathways, which are important for motor control in healthy individuals. They may also lead to paradigms capable of enhancing rehabilitation in patients recovering from damage, such as after stroke or spinal cord injury.

Instruction-dependent modulation of the long-latency stretch reflex is associated with indicators of startle.

Long-latency responses elicited by postural perturbation are modulated by how a subject is instructed to respond to the perturbation, yet the neural pathways responsible for this modulation remain unclear. The goal of this study was to determine whether instruction-dependent modulation is associated with activity in brainstem pathways contributing to startle. Our hypothesis was that elbow perturbations can evoked startle, indicated by activity in the sternocleidomastoid muscle (SCM). Perturbation responses were compared to those elicited by a loud acoustic stimulus, known to elicit startle. Postural perturbations and startling acoustic stimuli both evoked SCM activity, but only when a ballistic elbow extension movement was planned. Both stimuli triggered SCM activity with the same probability. When SCM activity was present, there was an associated early onset of triceps electromyographic (EMG), as required for the planned movement. This early EMG onset occurred at a time often attributed to long-latency stretch reflexes (75-100 ms). The nature of the perturbation-triggered EMG (excitatory or inhibitory) was independent of the perturbation direction (flexion or extension) indicating that it was not a feedback response appropriate for returning the limb to its original position. The net EMG response to perturbations delivered after a movement had been planned could be explained as the sum of a stretch reflex opposing the perturbation and a startle-evoked response associated with the prepared movement. These results demonstrate that rapid perturbations can trigger early release of a planned ballistic movement, and that this release is associated with activity in the brainstem pathways contributing to startle reflexes.

Massage and stretching reduce spinal reflex excitability without affecting twitch contractile properties.

Both stretching and massage can increase range of motion. Whereas the stretching-induced increases in ROM have been attributed to changes in neural and muscle responses, there is no literature investigating the ROM mechanisms underlying the interaction of stretch and massage. The objective of this paper was to evaluate changes in neural and evoked muscle responses with two types of massage and static stretching. With this repeated measures design, 30s of plantar flexors musculotendinous junction (MTJ) and tapotement (TAP) massage were implemented either with or without 1min of concurrent stretching as well as a control condition. Measures included the soleus maximum H-reflex/M-wave (H/M) ratio, as well as electromechanical delay (EMD), and evoked contractile properties of the triceps surae. With the exception of EMD, massage and stretch did not significantly alter triceps surae evoked contractile properties. Massage with and without stretching decreased the soleus H/M ratio. Both TAP conditions provided greater H/M ratio depression than MTJ massage while the addition of stretch provided the greatest inhibition. Both massage types when combined with stretching increased the duration of the EMD. In conclusion, MTJ and TAP massage as well as stretching decreased spinal reflex excitability, with TAP providing the strongest suppression. While static stretching prolongs EMD, massage did not affect contractile properties.

Mathematical model of fiber orientation in anisotropic fascia layers at large displacements.

A mathematical model is developed to determine the relationship between stretch and the orientation of fibers in the fascia. The transversely isotropic stress- strain relation for large displacements valid for the human fascia reinforced by the collagen fibers is employed. The relation between the orientation of fibers in the un-deformed and deformed state depending upon the stretch is plotted. It is observed that for greater fiber angle orientation, the fibers are more resistant to reorientation as the fascia is stretched longitudinally. It is also concluded that the reinforced fascia will always be in tension as the stretch is applied. However, we suggest future research to resolve the tension and compression issues in fascia.

Protocolo de actuación en el tratamiento defi nitivo de la fascitis plantar. Importancia de la férula nocturna antiequina / No disponible

En el trabajo presentado nos planteamos como objetivo conocer los aspectos clínicos y las maniobras exploratorias claves para llegar al diagnóstico correcto de la fascitis plantar, que nos ayudará a entender el patrón biomecánico como la causa principal, para así poder establecer un protocolo de actuación que contribuya a la desaparición de esta patología en un periodo corto de tiempo, con la ayuda, entre otros métodos, de la férula nocturna antiequina(AU)

In the presented work we considered as objective to know the clinical aspects and the exploratory maneuvers keys to come to the correct diagnosis of the plantar fasciitis, which will help us to understand the biomechanical pattern as the main cause, and to institute a protocol of action that contributes to the disappearance of this pathology in a short period of time, with the aid, among others methods, of the night splint(AU)

Inhibitory effect of needle penetration on vibration-induced finger flexion reflex in humans.

BACKGROUND: Vibration-induced finger flexion reflex (VFR) in the upper extremity is inhibited by needle insertion acupuncture to the large intestine 4 (LI4) at the hand. This claim has a limitation because the inhibitory effect is deduced only from reduction in the maximum finger flexion (FF) force during the tonic flexion reflex by vibratory stimulation after acupuncture. METHODS: The study was a crossover design with two conditions-acupuncture and control-to which 16 healthy volunteers were subjected. VFR in the upper extremity was induced by applying vibratory stimulation on the volar side of the middle fingertip of the right hand, before and after acupuncture at the right LI4 in 16 healthy volunteers. We measured the area under the curve (AUC) of finger flexion force and surface electromyogram (EMG) in the flexor muscles, in addition to the maximum FF force during vibratory stimulation. We compared AUC, surface EMG and maximum FF force in the acupuncture condition with those in the control condition. We also estimated the correlation between AUC, surface EMG and maximum FF force. RESULTS: AUC, surface EMG and maximum FF force were significantly reduced (p <0.01) after acupuncture compared with those of the control group. A strong correlation was observed in maximum FF force versus AUC (r=0.98, p <0.01) and surface EMG (r=0.77, p <0.01). CONCLUSIONS: Acupuncture at ipsilateral LI4 inhibited tonic activities in the finger flexor muscles during VFR, which suggests that afferent input with needle penetration has inhibitory effect on the motor neuronal activities in the reflex circuits of VFR.

The differential role of motor cortex in stretch reflex modulation induced by changes in environmental mechanics and verbal instruction.

The motor cortex assumes an increasingly important role in higher mammals relative to that in lower mammals. This is true to such an extent that the human motor cortex is deeply involved in reflex regulation and it is common to speak of "transcortical reflex loops." Such loops appear to add flexibility to the human stretch reflex, once considered to be immutable, allowing it to adapt across a range of functional tasks. However, the purpose of this adaptation remains unclear. A common proposal is that stretch reflexes contribute to the regulation of limb stability; increased reflex sensitivity during tasks performed in unstable environments supports this hypothesis. Alternatively, before movement onset, stretch reflexes can assist an imposed stretch, opposite to what would be expected from a stabilizing response. Here we show that stretch reflex modulation in tasks that require changes in limb stability is mediated by motor cortical pathways, and that these differ from pathways contributing to reflex modulation that depend on how the subject is instructed to react to an imposed perturbation. By timing muscle stretches such that the modulated portion of the reflex occurred within a cortical silent period induced by transcranial magnetic stimulation, we abolished the increase in reflex sensitivity observed when individuals stabilized arm posture within a compliant environment. Conversely, reflex modulation caused by altered task instruction was unaffected by cortical silence. These results demonstrate that task-dependent changes in reflex function can be mediated through multiple neural pathways and that these pathways have task-specific roles.

Reweighting sensory signals to maintain head stability: adaptive properties of the cervicocollic reflex.

A major goal of this study was to characterize the cervicocollic reflexes (CCRs) in awake squirrel monkeys and compare it to observations in cat. This was carried out by stabilizing the head in space while rotating the lower body. The magnitude and phase of the torque produced between the head and the restraint system was used as an indicator of the CCR. Many properties of the squirrel monkey's CCR were found to be similar to those of the cat. The torque decreased as a function of frequency and amplitude. In addition, the static level of torque increased with head eccentricity. One difference was that the torque was 90x smaller in squirrel monkeys. Biomechanical differences, such as differences in head inertia, could account for these differences. The second goal was to determine if the CCR was sensitive to increases in the head's inertia. To test this, we increased the head's inertia by a factor of 36 and allowed the reflexes to adapt by rotating the whole body while the head was free to move. The CCR was rapidly assessed by periodically stabilizing the head in space during whole-body rotations. The magnitude of the torque increased by nearly 60%, suggesting that the CCR may adapt when changes in the head's inertia are imposed. Changes in the torque were also consistent with changes in head-movement kinematics during whole-body rotation. This suggests that the collic reflexes may dynamically adapt to maintain the performance and kinematics of reflexive head movement.

Transcutaneous electrical nerve stimulation combined with task-related training improves lower limb functions in subjects with chronic stroke.

BACKGROUND AND PURPOSE: Previous studies have shown that repeated sensory inputs could enhance brain plasticity and cortical motor output. The purpose of this study was to investigate whether combining electrically induced sensory inputs through transcutaneous electrical nerve stimulation (TENS) with task-related training (TRT) in a home-based program would augment voluntary motor output in chronic stroke survivors better than either treatment alone or no treatment. METHODS: Eighty-eight patients with stroke were assigned randomly to receive a home-based program of (1) TENS, (2) TENS+TRT, (3) placebo TENS+TRT, or (4) no treatment (control) 5 days a week for 4 weeks. Outcome measurements included Composite Spasticity Scale, peak torques generated during maximum isometric voluntary contraction of ankle dorsiflexors and plantarflexors, and gait velocity recorded at baseline, after 2 and 4 weeks of treatment, and 4 weeks after treatment ended. RESULTS: When compared with TENS, the combined TENS+TRT group showed significantly greater improvement in ankle dorsiflexion torque at follow-up and in ankle plantarflexion torque at week 2 and follow-up (P<0.01). When compared with placebo+TRT, the TENS+TRT group produced earlier and greater reduction of plantarflexor spasticity and improvement in ankle dorsiflexion torque at week 2 (P<0.01). When compared with all 3 groups, the TENS+TRT group showed significantly greater improvement in gait velocity (P<0.01). CONCLUSIONS: In patients with chronic stroke, 20 sessions of a combined TENS+TRT home-based program decreased plantarflexor spasticity, improved dorsiflexor and plantarflexor strength, and increased gait velocity significantly more than TENS alone, placebo+TRT, or no treatment. Such improvements can even be maintained 4 weeks after treatment ended.

Voluntary modulation of human stretch reflexes.

It has been postulated that the central nervous system (CNS) can tune the mechanical behavior of a joint by altering reflex stiffness in a task-dependant manner. However, most of the evidence supporting this hypothesis has come from the analysis of H-reflexes or electromyogram (EMG) responses. Changes in overall stiffness have been documented but, as yet, there is no direct evidence that the CNS can control reflex stiffness independently of the intrinsic stiffness. We have used a novel identification algorithm to estimate intrinsic and reflex stiffness and feed it back to subjects in real-time. Using this biofeedback, subjects could learn to control reflex stiffness independently of intrinsic stiffness. At low torque levels, subjects could vary their reflex stiffness gain by a factor of 4, while maintaining elastic stiffness and torque constant. EMG measurements confirmed that the contraction levels of the ankle muscles remained constant. Further experiments showed that subjects could change their reflexes rapidly on command. Thus, we conclude that the CNS can control reflex stiffness independently and so has great flexibility in adjusting the mechanical properties of a joint to meet functional requirements.

Fundamentos biológicos de la elongación según tiempo de estiramiento y actividad contráctil / Biological background of stretching according to time and lengthening contractile activity

Se analizaron los fundamentos biológicos de las técnicas de elongación muscular, en relación con dos variables: tiempo de mantención y presencia de actividad contráctil antes o durante la aplicación del estiramiento. Se busca así hacer un análisis comparativo de los principios de dos métodos: el Stretching Global Activo, y el contraer-relajar, una modalidad basada en la Facilitación Neuromuscular Propioceptiva. Se producen dos respuestas, conceptualmente distintas: a)la disminución de la tensión que genera el músculo en reposo, y b) la elongación muscular propiamente tal. La primera, conocida como relajación de fuerza es una adaptación a corto plazo, atribuído a la conducta viscoelástica del Tejido Conectivo Intramuscular, y se evidencia por una disminución del torque pasivo de aprox. un 30 por ciento. La segunda respuesta corresponde a una adaptación a largo plazo, por aumento real de la longitud del vientre muscular, e implica una adición de sarcómeros en serie. Los estiramientos breves, con o sin contracción previa del músculo, producen relajación de fuerza, cuyo efecto no excede los 60'; a largo plazo, producen aumento de rango de movimiento, pero sin modificar la pendiente de la curva torque / rango, de lo que se deduce que, más que una elongación real, existe sólo una mayor tolerancia al estiramiento , Según evidencia en modelo animal, la verdadera elongación se lograría sólo con tiempos prolongados de estiramiento, o con una sumación de una gran cantidad de estiramientos breves. La contracción isométrica durante el estiramiento amplificaría la adición de sarcómeros en serie. Se concluye que los fundamentos del Stretching Global Activo están más respaldados por la evidencia que los de la elongación realizada con principios de Facilitación Neuromuscular, aunque ambos son útiles dependiendo del propósito.

Cortical control of muscle relaxation: a lateralized readiness potential (LRP) investigation.

OBJECTIVE: We used the lateralized readiness potential (LRP) to investigate cortical mechanisms underlying the termination of muscle contraction. Active suppression and withdrawal of activation have been proposed as underlying mechanisms in isotonic and isometric relaxation. METHODS: Experiment 1 investigated isotonic wrist extension/release from extension. Experiment 2 investigated isometric activation/relaxation of a pinch grip. Tasks were performed with left and right hands and cued auditorily at variable intervals. EEG was recorded from 128 electrodes and processed to derive the LRP timelocked to the onset and offset of muscle contraction. RESULTS: LRPs for isotonic activation and relaxation were of identical amplitude at electrodes overlying the motor cortex, but differed at frontal locations due to higher amplitude re-afferent activity during activation. The isometric LRP was significantly smaller during relaxation than during activation, without differences in scalp distribution. CONCLUSION: The LRP findings confirm differences between isotonic and isometric relaxation, which may be partly explained by the need to suppress a stretch reflex in the former condition. The presence of an LRP associated with isometric relaxation reveals active preparation in the motor cortex, indicating that muscle relaxation in the isometric task cannot be explained solely by withdrawal of activation. SIGNIFICANCE: High-density LRP recordings isolate different cortical mechanisms underlying the termination of muscle contraction.

Stretch reflex and Hoffmann reflex responses to osteopathic manipulative treatment in subjects with Achilles tendinitis.

CONTEXT: Irvin M. Korr, PhD, hypothesized that sensitivity of the monosynaptic stretch reflex (ie, deep tendon reflex) plays a major role in the restriction-of-motion characteristic of somatic dysfunction, and that restoration of range of motion through osteopathic manipulative treatment (OMT) could be achieved by resetting of the stretch receptor gain. OBJECTIVE: To test Korr's hypothesis in the context of Achilles tendinitis, examining whether OMT applied to patients with Achilles tendinitis reduces the strength of the stretch reflex. METHODS: Subjects were recruited through public advertisements and referrals from healthcare professionals. There were no recruitment restrictions based on demographic factors. Amplitudes for stretch reflex and H-reflex (Hoffmann reflex) in the triceps surae muscles (the soleus together with the lateral and medial heads of the gastrocnemius) were measured in subjects with diagnosed Achilles tendonitis (n=16), both before and after OMT. These measurements were also made in asymptomatic control subjects (n=15) before and after sham manipulative treatment. RESULTS: As predicated on the concepts of the strain-counterstrain model developed by Lawrence H. Jones, DO, the use of OMT produced a 23.1% decrease in the amplitude of the stretch reflex of the soleus (P<.05) in subjects with Achilles tendinitis. Similarly significant responses were measured in the lateral and medial heads of the gastrocnemius in OMT subjects. The H-reflex was not significantly affected by OMT. In control subjects, neither reflex was significantly affected by sham manipulative treatment. By using a rating scale on questionnaires before treatment and daily for 7 days posttreatment, OMT subjects indicated significant clinical improvement in soreness, stiffness, and swelling. CONCLUSION: The reduction of stretch reflex amplitude with OMT, together with no change in H-reflex amplitude, is consistent with Korr's proprioceptive hypothesis for somatic dysfunction and patient treatment. Because subjects' soreness ratings also declined immediately after treatment, decreased nociceptor activity may play an additional role in somatic dysfunction, perhaps by altering stretch reflex amplitude.

Effect of counterstrain on stretch reflexes, hoffmann reflexes, and clinical outcomes in subjects with plantar fasciitis.

CONTEXT: Previous research indicates that osteopathic manipulative treatment based on counterstrain produces a decrease in the stretch reflex of the calf muscles in subjects with Achilles tendinitis. OBJECTIVES: To study the effects of counterstrain on stretch reflex activity and clinical outcomes in subjects with plantar fasciitis. METHODS: In a single-blind, randomized controlled trial of crossover design, the effects of counterstrain were compared with those of placebo in adult subjects (N=20) with plantar fasciitis. The subjects were led to believe that both the counterstrain and placebo were therapeutic modalities whose effects were being compared. Ten subjects (50%) were assigned to receive 3 weeks of counterstrain treatment during phase 1 of the trial, while the other 10 subjects were given placebo capsules. After a 2- to 4-week washout period, phase 2 of the trial began with the interventions reversed. Clinical outcomes were assessed with daily questionnaires. Stretch reflex and H-reflex (Hoffmann reflex) in the calf muscles were assessed twice during each laboratory visit, before and after treatment in the counterstrain phase. RESULTS: No significant changes in the electrically recorded reflexes of the calf muscles were observed in response to treatment. However, changes in the mechanical characteristics of the twitches resulting from the electrical responses were observed. Peak force and time to reach peak force both increased (P< or =.05) in the posttreatment measurements, with the increase being significantly more pronounced in the counterstrain phase (P< .05). A comparison of pretreatment and posttreatment symptom severity demonstrated significant relief of symptoms that was most pronounced immediately following treatment and lasted for 48 hours. CONCLUSIONS: Clinical improvement occurs in subjects with plantar fasciitis in response to counterstrain treatment. The clinical response is accompanied by mechanical, but not electrical, changes in the reflex responses of the calf muscles. The causative relation between the mechanical changes and the clinical responses remains to be explored.

Decrease in anterior knee laxity by electrical stimulation of normal and reconstructed anterior cruciate ligaments.

We have investigated the changes in anterior laxity of the knee in response to direct electrical stimulation of eight normal and 45 reconstructed anterior cruciate ligaments (ACLs). In the latter, the mean time from reconstruction was 26.7 months (24 to 32). The ACL was stimulated electrically using a bipolar electrode probe during arthroscopy. Anterior laxity was examined with the knee flexed at 20 degrees under a force of 134 N applied anteriorly to the tibia using the KT-2000 knee arthrometer before, during and after electrical stimulation. Anterior tibial translation in eight normal and 17 ACL-reconstructed knees was significantly decreased during stimulation, compared with that before stimulation. In 28 knees with reconstruction of the ACL, in 22 of which the grafts were found to have detectable somatosensory evoked potentials during stimulation, anterior tibial translation was not decreased. These findings suggest that the ACL-hamstring reflex arc in normal knees may contribute to the functional stability and that this may not be fully restored after some reconstructions of the ACL.

Effect of lower limb massage on electromyography and force production of the knee extensors.

OBJECTIVE: To evaluate the effect of massage on force production and neuromuscular recruitment. METHODS: Ten healthy male subjects performed isokinetic concentric contractions on the knee extensors at speeds of 60, 120, 180, and 240 degrees /s. These contractions were performed before and after a 30 minute intervention of either rest in the supine position or lower limb massage. Electromyography (EMG) and force data were captured during the contractions. RESULTS: The change in isokinetic mean force due to the intervention showed a significant decrease (p<0.05) at 60 degrees /s and a trend for a decrease (p = 0.08) at 120 degrees /s as a result of massage compared with passive rest. However, there were no corresponding differences in any of the EMG data. A reduction in force production was shown at 60 degrees /s with no corresponding alteration in neuromuscular activity. CONCLUSIONS: The results suggests that motor unit recruitment and muscle fibre conduction velocity are not responsible for the observed reductions in force. Although experimental confirmation is necessary, a possible explanation is that massage induced force loss by influencing "muscle architecture". However, it is possible that the differences were only found at 60 degrees /s because it was the first contraction after massage. Therefore muscle tension and architecture after massage and the duration of any massage effect need to be examined.

Movement analysis in neonates with spina bifida aperta.

INTRODUCTION: In neonates with spina bifida aperta (SBA), leg movements by myotomes caudal to the meningomyelocele (MMC) are transiently observed. It is unclear whether these leg movements relate to functional neural conduction through the MMC. For optimal therapeutical intervention, pathophysiological insight in these transient leg movements seems relevant. If leg movements by myotomes caudal to the MMC concur with the execution of general movements (GMs), functional neural conduction through the MMC is implicated. OBJECTIVE: In neonates with SBA, we aimed to determine whether the transiently present leg movements caudal to the MMC indicate functional neural conduction through the MMC. METHODS: During the perinatal period, fetuses and neonates with SBA (n = 7 and n = 13, respectively) were longitudinally analysed for concurrency between leg movements caudal to the MMC and GMs. To address the integrity of the reflex arc in spinal segments (at, or) caudal to the MMC, tendon leg reflexes were assessed during the first postnatal week. RESULTS: At postnatal day 1, leg movements caudal to the MMC concurred with GMs in 12 of 13 infants. Isolated leg movements were observed in only 3 of these 12 infants (isolated vs. concurrent; p < 0.005). Leg movements concurring with GMs lasted longer than isolated leg movements (median duration = 11 s vs. 2 s; p < 0.05). Between days 1 and 7, tendon leg reflexes (at, or) caudal to the MMC had disappeared in all but 1 neonate. However, leg movements caudal to the MMC remained concurrently present with GMs in all five neonates available for follow-up after day 7. Comparing these leg movements between days 1 and 7 indicated a decreased duration (-44%, p < 0.05). CONCLUSIONS: In neonates with SBA, leg movements caudal to the MMC concur with GMs, indicative of functional neural conduction through the MMC. The disappearance of these leg movements is caused by lower motor neuron dysfunction at the reflex arc, whereas neural conduction through the MMC is still functional.

[Evoked potentials of the somatic cortex, thalamus, and electromyographic reactions of the cat shoulder muscles elicited by elbow joint straightening in norm and after injection of neurotoxin].

EMG activity from the elbow joint muscles and evoked potentials (ep) from the somatic cortex (fields 4, 6) and thalamic nuclei (vl, vpl) elicited by passive extension were recorded in the unanesthetized cats before and after MPTP injection (total dose 10 mg/kg). It was shown, that after MPTP injection changes of the EMG response in cats are similar to that observed in parkinsonian patients: The increase of amplitude and duration of the stretch-related m2-3 -components of EMG, as well as excitation increase in thalamus and cortex was shown after MPTP. Perturbation of an external extensor loading applied to the forearm with different fixed force moments elicited m. biceps brachii EMG reactions which amplitude in norm correlated with a muscle stretch size. The MPTP injection influenced this dependence. Contrary to EMG responses n26-60 amplitude of the thalamic and cortical EP did not depend on the level of muscle stretch neither in norm nor after MPTP injection. Hence it supposed that an afferent excitation, which was responsible for this EP, did not take part in a generation of the m2-components of the stretch reflex. Late (n100) component's amplitude of the thalamic nuclei EP depended on the muscle stretch level. After MPTP injection this relation disappeared just as in the EMG responses. Since m2 components aroused in the spinal cord motor neurons earlier than n100 components in thalamus it is supposed that excitation of shoulder muscle receptors and spinal neurons, which provided with origin of m2 components consisting of EMG responses, were responsible for generation of the EP late components of thalamic nuclei VL and VPL.

Intraoperative direct mechanical stimulation of the anterior cruciate ligament elicits short- and medium-latency hamstring reflexes.

The anterior cruciate ligament (ACL) has not only a mechanical but also a sensorimotor function. Patients with injuries of the ACL frequently complain of knee instability despite good mechanical stabilization after surgical reconstruction. Compared with healthy subjects, their latencies of hamstring reflexes after anterior tibia translation are considerably increased. There is evidence for the existence of a reflex arc between the ACL and the hamstrings. The aim of this study was to determine if there is a direct reflex response after an isolated mechanical stimulation of the ACL in humans. In 10 patients who underwent arthroscopy, hamstring electromyographic (EMG) responses were assessed intraoperatively after applying an isolated load on the ACL. Latencies, amplitudes, and integrals of the EMG responses were analyzed. In four patients, the measurements were repeated after injection of local anesthetics into the ACL. In all subjects, responses with mean latencies of 42 +/- 4.4 (SD) ms corresponding to a medium latency response (MLR) were found. In seven subjects, they were preceded by responses with a short-latency (SLR) of 24 +/- 2.7 ms. The maximum amplitude was 8.6 +/- 7 mV, the integral 0.064 +/- 0.05 mV*s. The injection of local anesthetics reduced the amplitude by 34 +/- 12% and the integral by 50 +/- 20%. Direct mechanical stimulation of the ACL evokes considerably smaller SLRs and MLRs than anterior tibia translation during standing. It is argued that latency changes observed in patients with ACL ruptures may be rather due to changes in the sensorimotor integration of the afferent input from the knee joint than to the absence of the direct ACL reflex.