[Electrophysiological demonstration of proprioceptive muscle afferents & of the monosynaptic reflex are of the internal laryngeal muscle].
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Humans↗
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Results for “REFLEX, PROPRIOCEPTIVE”
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Role of proprioception in the control of lid position during reflex and conditioned blink responses in the alert behaving cat.
The contribution of the orbicularis oculi muscle to the determination of lid position, and the putative role of eyelid proprioception in the control of reflex and conditioned eye blinks, were studied in alert behaving cats. Upper lid movements and the electromyographic activity of the orbicularis oculi muscle were recorded during reflexively evoked blinks and during the classical conditioning of the eyelid response. Blinks were evoked by air puffs, flashes and electrical stimulation of the supraorbitary branch of the trigeminal nerve. Eyelid responses were conditioned with a trace classical conditioning paradigm consisting of a short, weak air puff, followed 250 ms later by a long, strong air puff. Orbicularis oculi muscle activation during reflex blinks was independent of lid position and was not modified by the presence of weights acting in the upward or downward directions. Local anesthesia of the supraorbital nerve reduced blinks evoked by air puffs applied to the lower jaw, but did not affect flash-evoked blinks. No relationship was established between initial lid position and the first downward component of conditioned eyelid responses. In contrast, initial lid position was related to the first upward component of the same conditioned response. It is concluded that orbicularis oculi motor units receive no feedback proprioceptive signals from the eyelid, other than those coming from cutaneous receptors, and that lid position is determined by the activity of the levator palpebrae superioris muscle. The lack of sensory information about lid position in facial motoneurons probably has some functional implications on the central control of cognitive and emotional facial expressions.
Air↗
Proprioceptive inputs to nonspiking local interneurons contribute to local reflexes of a locust hindleg.
Local reflexes of a leg of the locust Schistocerca gregaria (Forskal) can be elicited by selective stimulation of a proprioceptor (the femoral chordotonal organ) at the femorotibial joint. Motor neurons are either excited or inhibited, so that a coordinated reflex response of a leg results. At the same time, some nonspiking local interneurons are either excited or inhibited by the inputs from these proprioceptive afferents. Altering the membrane potential of an individual, nonspiking interneuron can either increase or decrease the response of the participating motor neurons to the proprioceptive stimulus and thereby alter the gain of the reflex. To determine the pathways, and to understand the role of the nonspiking interneurons in mediating these reflex effects, recordings were made simultaneously from these interneurons and afferent neurons. The excitation of a particular nonspiking local interneuron is produced monosynaptically by the afferent neurons. Chemically mediated EPSPs consistently follow sensory spikes with a latency that is the same as that for the known parallel, direct connections made by these sensory neurons with motor neurons (Burrows, 1987a). The chordotonal afferents and the branches of the local interneurons project to the same regions of neuropil. In contrast, the simplest inhibitory pathway is disynaptic, involving spiking local interneurons. The afferents make direct excitatory connections with some of these spiking interneurons, which then make direct inhibitory connections with a nonspiking interneuron. Interactions between the local interneurons add to the complexity of the pathways.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Spinal and supraspinal effects of activity in ligament afferents.
In this paper available knowledge on effects from joint and ligament afferents on spinal neurones and pathways are briefly reviewed, and possible functional implications discussed. Ligament afferents may contribute to joint stability, muscle coordination and proprioception through direct polysynaptic reflex effects onto ascending pathways and skeletomotoneurones, and/or indirectly via reflex actions on the gamma-muscle spindle system. Theoretical and experimental evidence indicate that ligament afferents, together with afferents from other joint structures, muscles and the skin, provide the CNS with information on movements and posture through ensemble coding mechanisms, rather than via modality specific private pathways. The existence and functional relevance of ligamentomuscular protective reflexes, that are triggered when the ligament is threatened by potentially harmful loads, has been seriously questioned. It seems more likely that peripheral sensory inputs from ligament afferents participate in a continuous control of the muscle activity through feedforward, or preprogramming, mechanisms. In line with these ideas it has been suggested that ligament mechanoreceptors have an important role in muscle coordination and in the reflex regulation of the functional joint stability, by contributing to the preprogramming of the muscle stiffness through reflex modulation of the gamma-muscle spindle system.
Afferent Pathways↗
Passive sustained turning of the head induces asymmetric gain of the vestibulo-ocular reflex in healthy subjects.
In order to test the hypothesis of an interaction between neck proprioception and the vestibulo-ocular reflex (VOR), we rotated 16 healthy subjects both facing forward and with their heads passively turned 70 degrees to either side. We found that gain tended to be lower when the subjects were rotated with their heads turned opposite to the direction of rotation compared to when they were rotated in the same direction, but facing forward. Although our findings were not statistically significant, they suggest that there is a measurable interaction between neck proprioception and the VOR in subjects with normal vestibular function. Asymmetric neck muscle proprioceptive signals seem to give rise to asymmetric functioning of the VOR, which, at least in part, could be the pathogenesis of cervical dizziness. If so, this could lead to misinterpretation of vestibular assessments in patients with neck pain who also complain of dizziness.
Adult↗
Pathophysiology of motor functions in prolonged manned space flights.
The influence of weightlessness on different parts of the motor system have been studied in crew members of 140 and 175 days space flights. It has been shown that weightlessness affects all parts of the motor system including (i) the leg and trunk muscles, in which severe atonia, a decrease of strength and an increase of electromyographic cost of contraction have been observed, (ii) the proprioceptive elements and the spinal reflex mechanisms in which decreased thresholds accompanied by decreases of maximal amplitude of reflexes and disturbances in cross reflex mechanisms have been found. and (iii) the central mechanisms that control characteristics of postural and locomotor activities. The intensities and durations of disturbances of different parts of the motor system did not correlate to each other, but did correlate with prophylactic activity during space flight. The data suggest a different nature of disturbances caused by weightlessness in different parts of the motor system.
Electromyography↗
Modulation of the startle response during human gait.
While many studies have shown that there is a phase-dependent modulation of proprioceptive and exteroceptive reflexes during gait, little is known about such modulation for auditory reflexes. To examine how startle reactions are incorporated in an ongoing gait pattern, unexpected auditory stimuli were presented to eight healthy subjects in six phases of the step cycle during walking on a treadmill at 4 km/h. For both legs, electromyographic activity (EMG) was recorded in the biceps femoris (BF), the rectus femoris (RF), the tibialis anterior (TA), and the soleus (SO). In addition, stance and swing phases of both legs, along with knee angles of both legs and the left ankle angle, were measured. All subjects showed various response peaks. Responses with latencies of approximately 60 ms (F1), approximately 85 ms (F2), and approximately 145 ms (F3) were found. The amplitude of the reflex responses was dependent on the timing of the startle stimulus in the step cycle. Although the startle response habituated rapidly, the phase-dependent modulation pattern generally remained the same. The phase-dependent amplitude modulations were not strictly correlated with the modulation of the background activity. The TA even showed a transition from facilitatory F2 responses during stance to suppressive responses during midswing. Responses were observed in both flexors and extensors, often in coactivation, especially during stance. Furthermore the gait characteristics showed a shortening of the subsequent step cycle and a small decrease in the range of motion of ankle and knees. These results suggest that the responses are adapted to achieve extra stability dependent on the phase of the step cycle. However, even in the first trials, the changes in kinematics were small allowing a smooth progression of gait.
Adult↗
Impaired modulation of the vestibulo-ocular reflex in Huntington's disease.
The vestibulo-ocular reflex (VOR) stabilizes gaze during movement, in conjunction with other afferent information: visual, proprioceptive, and somaesthetic. The reflex can either be augmented or suppressed, depending on visual requirements, and undergoes long-term adaptation to compensate for physical changes in the subject. Importantly, over relatively short periods of time, the VOR should function consistently under the same circumstances. This study examines VOR function in patients with Huntington's disease (HD), with a view to investigating cortical influences on the reflex. Horizontal eye movements were recorded in 9 patients with HD and 7 normal subjects, using the scleral search coil technique, in response to high frequency, unpredictable head rotations imposed manually. To establish base VOR function, recordings were made in darkness, without instruction, before and after wearing x2 magnifying lenses for a period of 2 hours to adapt the reflex. Recordings were also made before adaptation, while fixating a stationary visual target (VOR augmentation), and while fixating a target moving with the head (VOR suppression). Although results suggest that the VOR is preserved in HD, with relatively normal gain values and appropriate augmentation and suppression of the reflex with visual input, patients were unable to adapt the VOR to altered visual conditions. This represents a novel finding in HD and suggests that cortical structures compromised in HD exert influences on the long-term adaptation of the VOR.
Adult↗
H-reflex changes during static stretching and two variations of proprioceptive neuromuscular facilitation techniques.
The effects of 3 stretching methods on the motor pool excitability of the soleus muscle as measured by the Hoffmann reflex have been compared with the objective of revealing central nervous system influences promoting muscle compliance to lengthening. The H-wave was reduced slightly throughout the static stretch method. The contract-relax (CR) method produced profound inhibition during the first several hundred milliseconds following contraction, but gradually increased to values similar to static stretch (SS) values 2 sec following contraction. Hoffmann reflex values for the contract-relax-antagonist-contract (CRAC) method were greatly depressed throughout the stretching phase with a slight increase after 2 sec. It was concluded that several inhibitory neural influences can have an additive effect in profoundly reducing motor pool excitability. Under the assumption that greater motor pool inhibition reduces muscle contractibility and therefore allows more muscle compliance, it is suggested that the proprioceptive neuromuscular facilitation (PNF) methods, particularly those involving reciprocal activation, provide the greatest potential for muscle lengthening. This is supported by previous studies which compared gains in range of motion using these 3 stretching methods (Holt et al. 1970; Moore and Hutton 1980; Etnyre and Abraham 1985).
Adult↗
Monosynaptic reflexes in falling man.
We have examined peripheral proprioceptive input during fall in man. The first 80 ms of unexpected free fall, both in a parachute harness and while seated, has been studied using the monosynaptic Hoffman (H) and Achilles tendon (T) reflexes. Facilitation of the H reflex begins about 30 to 40 ms after release, representing the onset of motor neurone facilitation before the electromyographic activity which begins about 80 ms after release. Earlier facilitation of the T reflex may represent spindle excitation due to change in muscle shape as suggested by Matthews and Whiteside (1960), but the T reflex inhibition described by these authors after 50 ms of seated fall is probably a purely mechanical phenomenon.
Achilles Tendon↗
[Value of muscular proprioceptive afferents in stabilization of Hoffmann's reflex].
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Humans↗
[Role of ocular muscle proprioception in the maintenance of body equilibrium with particular reference to the cervical reflex].
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Adult↗
Sensory reinnervation of muscles following nerve section and suture in cats.
The common peroneal nerve was transected and repaired by epineurial suture in nine cats. In a further nine the nerve was transected twice and similarly repaired so as to produce a short autograft. Recovery of stretch receptors in peroneus brevis was monitored histologically and physiologically from six to fifty weeks. In recovery after single neurotomy functionally identifiable muscle-spindle and tendon-organ afferents were reduced to 25% and 45% of normal, respectively; after double neurotomy (autograft) both were reduced to about 10% of normal. Muscle spindles were reinnervated with annulospiral terminals, or wholly abnormal fine axon terminals, or both. Recovery evidently entails not only a reduction in number of stretch afferents, but also the making of some incorrect reconnections that presumably result in abnormal proprioceptive feedback and reflex action. When a graft is used the sensory impairment is compounded.
Animals↗
Time constants of vestibular nuclei neurons in the goldfish: a model with ocular propioception.
A simple model of the vestibular-ocular reflex with a proprioceptive eye velocity feedback loop is used to simulate recent data on the vestibular responses of neurons in the vestibular nuclei of spinal goldfish. The data support the hypothesis that a proprioceptive feedback loop elongates the vestibular nucleus time constant to equal that of the slow phase eye movements of vestibular nystagmus.
Animals↗
Muscle spindle activity in the affected upper limb after a unilateral stroke.
Weakness, loss of dexterity and exaggerated reflex responses to proprioceptive and cutaneous stimuli are typical features of hemiparetic stroke. Since the extent to which altered fusimotor drive contributes to these deficits has not been established, this study was designed to assess fusimotor function in stroke patients by comparing three aspects of muscle spindle afferent behaviour (background discharge rate, responses to reflex inputs and responses to voluntary contractions) in 11 subjects affected by recent cerebrovascular lesions, with those in 18 healthy volunteers. The mean background discharge rates of muscle spindle afferents in the radial nerve when subjects attempted to relax the recorded limb completely were 6.6 +/- 5.3 Hz (n = 26) in patients and 6.4 +/- 6.1 Hz (n = 76) in control subjects. The variability of discharge rate of active afferents was also similar (0.12 +/- 0.07 and 0.09 +/- 0. 10, respectively). Reflex activation of fusimotor neurons was assessed using trains of electrical stimuli to the superficial radial nerve or to the palm of the hand, and using natural skin stimuli. Neither type of cutaneous stimulation affected muscle spindle afferent discharge in the absence of an EMG response. During deliberate voluntary contractions muscle spindle discharge rates were enhanced similarly in both the control and patient groups, indicating that volitional drives could access fusimotor neurons in the patients. Qualitatively, spindle behaviour was similar in patients and control subjects. These findings suggest that fusimotor function is not disturbed any more or less than skeletomotor function in hemiparetic patients and it is concluded that fusimotor dysfunction probably contributes little to their deficit.
Acoustic Stimulation↗
Inhibitory effect of acupuncture on the vibration-induced finger flexion reflex in man.
Experiments were performed on 12 young and healthy subjects. The palmar side of the index finger was vibrated with a triangular wave form at randomly changed inter-stimulus intervals. This vibratory stimulation elicited a flexion movement of the index finger, which was depressed by acupuncture at 'Wai-Kuan.' It was generally observed that the depressive effect developed slowly and lasted for a long time. The depressive effect of acupuncture on this reflex was analyzed using a cross-correlation between the vibratory stimuli and motor unit spikes recorded from the flexor digitorum communis muscle. Cross-correlograms revealed two types of reflex responses. One of them showed a peak of time-locked spikes to the vibratory stimuli at a latency of 25 msec, which indicates monosynaptic activity of the motoneuron, and also showed time-unlocked spikes distributed in both sides of the peak, which implies polysynaptic activity. This type of response was frequently observed and was supposed to be elicited by the proprioceptive tonic vibration reflex. The other revealed no peaks, which indicates that only time-unlocked spikes to the stimuli are generated, and that these spikes are evoked via polysynaptic pathway. This type of response was supposed to be elicited by so-called exteroceptive vibration-induced finger flexion reflex. Since both types of reflex responses, i.e., mono- and polysynaptic ones, were equally depressed during acupuncture, it was concluded that the excitability of the motoneuron, a common output of this reflex, is lowered by acupuncture.
Acupuncture Therapy↗
Mechanism of the vibration paradox: excitatory and inhibitory effects of tendon vibration on single soleus muscle motor units in man.
1. The parameters of presynaptic inhibition of the Ia spindle afferents from soleus muscle by vibration have been investigated. The inhibitory effects increase with the amplitude of vibration, but decrease when the vibration frequency is increased.2. The monosynaptic reflex threshold of twenty-one single soleus motor units activated in the H (Hoffmann) reflex by a single electrical stimulus to the posterior tibial nerve was estimated quantitatively and expressed in relation to the size of the simultaneously recorded H reflex.3. A parametric study of the effects of various Achilles tendon vibrations on the reflex threshold of the single soleus motor units indicated that their order of derecruitment is concordant with their rank order for activation in the phasic reflexes of the soleus. The last recruited motoneurones are the most susceptible to being silenced by steady vibration.4. Muscle vibration progressively recruits single motor units according to the motoneurone size principle through polysynaptic proprioceptive pathways. However the presynaptic inhibition of Ia spindle afferents simultaneously induced by the vibration works in reverse on the same rank order of motoneurones of the soleus spinal pool, thereby limiting the polysynaptic recruitment of units in the tonic vibration reflex while depressing the autogenic phasic proprioceptive reflexes. These mechanisms elucidate the so-called vibration paradox and extend the size principle of Henneman to presynaptic inhibitory effects.
Achilles Tendon↗
[Role of optokinetic stimulation in realizing vestibulospinal reflexes].
This paper presents data about the effect of optokinetic stimulation (OKS) on vestibulospinal reflexes and discusses mechanisms of interaction of the vestibular, optic and proprioceptive sensors during their combined stimulation. The vestibulospinal reflexes were investigated using a 2-minute step test and simultaneous OKS that was produced by a portable optokinetic drum mounted on the head of the test subject. During the tests optokinetic nystagmus was recorded and the angle of body rotation relative to the initial position was measured. It was found that during the step test the body turned along the OKS direction, i. e. towards the slow component of optokinetic nystagmus. During leftward OKS the angle of rotation was larger than during rightward OKS: 406.4 +/- 75.9 deg and 207.5 +/- 40.7 deg, respectively. During leftward OKS loss of equilibrium was recorded 4.5 times more often than during rightward OKS. It has been demonstrated that the capacity to track stimuli moving to the left is lower than that to pursue stimuli moving to the right. It has been shown that there is a correlation between the rate of the optokinetic nystagmus slow phase and the angle of body rotation during the step test. It has been concluded that optokinetic nystagmus can be used as an informative parameter when measuring statokinetic stability in response to multisensory stimulation.
Adult↗