Proprio-vegetative reflexes in relation to bodily equilibrium: clinical observations on pupillary reactions in patients with neck and lumbar pain following whiplash injury.
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Adult↗
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Results for “REFLEX, PROPRIOCEPTIVE”
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Functional organization of the spinal reflex pathways from forelimb afferents to hindlimb motoneurones in the cat.
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Afferent Pathways↗
Tonic vibration reflexes and background force level.
On Earth, the functional stretch reflex is an important component in the maintenance of posture and muscle tone. In parabolic flight experiments, we evaluated whether the functional stretch reflex, as reflected in the tonic vibration reflex, adjusts appropriately for changes in background gravitoinertial force level. Virtually immediate alterations of appropriate sign occurred.
Forearm↗
Effect of load disturbances during centrally initiated movements.
1. We have investigated the relative contributions of mechanical and reflex mechanisms in generating the forces produced by the neck muscles when loads were unexpectedly applied during centrally programmed head movements in monkeys. These movements, subserved by muscles well endowed with muscle spindles, are part of the coordinated eye-head response to the appearance of a stimulus in the animal's visual field. Our preparation was a chronically vestibulectomized monkey trained to make a visual discrimination. 2. Two procedures were used to evaluate the torque generated by the neck musculature when an unexpected load disturbance was applied: first, by surgically interrupting the afferent loop subserving the reflex action (section of cervical dorsal roots) and second, by building a mathematical model of the head-neck system and carrying out a process of simulation. 3. Our results indicated that the compensatory torque of reflex origin stimulated by the application of an opposing force was less than 10--30% of that required for perfect compensation, and the larger fraction of the observed compensation was due to the mechanical properties (inertial, viscous, and elastic) of the neck musculature. The combined action of reflex and mechanical processes never completely compensated for the disturbance.
Animals↗
Jaw-tongue reflex: afferents, central pathways, and synaptic potentials in hypoglossal motoneurons in the cat.
The tongue position is reflexively controlled by the jaw position (the jaw-tongue reflex). The purpose of this study was to clarify the mechanism of this reflex in terms of afferents, central pathways, and synaptic potentials in hypoglossal motoneurons in the cat. Intracellular recordings from hypoglossal motoneurons revealed that electrical stimulation of the temporalis muscle nerve evoked excitatory and inhibitory post-synaptic potentials in hypoglossal motoneurons. The threshold of temporalis muscle nerve stimulation for evoking the synaptic potentials was higher than 2.0 times the nerve threshold. The amplitude of the potentials increased with stimulus intensity up to 5.0 times the nerve threshold. Punctate light pressure applied to the temporalis muscle induced a tonic depolarizing potential in hypoglossal motoneurons on which action potentials as well as depolarizing synaptic activation noise were superimposed. On the other hand, electrical stimulation of the temporalis muscle during jaw-opening could slightly inhibit the electromyographic activities in the genioglossus and styloglossus muscles. Lesions including the Probst's tract at the level caudal to the trigeminal motor nucleus abolished both excitation and inhibition in hypoglossal motoneurons induced by tonic depression of the lower jaw, but exerted no effects on either the tonic stretch reflex or the trigemino-hypoglossal reflex. In contrast, lesions including the trigeminal spinal tract produced no changes in either excitation or inhibition of hypoglossal motoneurons induced by temporalis muscle afferents, whereas the excitation of hypoglossal motoneurons was abolished by the lesions. We conclude that the group II muscle spindle afferents from the temporalis muscle are primarily responsible for evoking the jaw-tongue reflex.
Afferent Pathways↗
Development and maturation of postural reflexes in normal kittens.
In order to evaluate neurologic development, postural reflexes were tested in normal kittens from birth through 7 weeks of age until stable adult patterns of performance were attained. These reflex tests included: body and air righting, visual placing, chin placing, tactile placing, hopping, and locomotion. A protocol for scoring responses was designed for each individual reflex to differentiate their progression. The first reflexes to mature were visual placing, chin placing, and body righting which attained a maximal score during the 3rd week of life. This was followed by maturation of the forelimb hopping reflex and independent locomotion during the 4th week. Forelimb tactile placing responses, hind limb hopping reflexes, and air righting developed by the 5th week. Hind limb tactile placing responses were the last to mature. They became fully expressed in the 6th week. The pattern of ontogeny of these reflexes proceeded in a cephalocaudal direction. This is in agreement with earlier observations of others who correlated the maturation of reflex responses in kittens with myelination in the central nervous system.
Aging↗
Age, functional postural reflexes, and voluntary sway.
This experiment considered age-related changes in functional relationships between postural reflexes and voluntary movement. Young and older adults received horizontal perturbations during normal stance and when engaged in voluntary sway. Electromyographic activity showed that (a) older adults had poorer coordination between postural reflexes and voluntary movement, and (b) their stabilizing responses to postural disturbances during voluntary sway were slower. In addition, the onsets of activity of functionally important muscles were less tightly bilaterally coupled, and patterns of muscle onsets were less stereotypically organized in older adults. The results suggest that older adults experience some breakdown in the timing and sequencing of muscle activity and in the functional coordination of their postural reflexes with voluntary sway.
Adolescent↗
Postural reflexes in cranial muscles in man.
Using electromyographic recording techniques, tonic neck reflexes and tonic labyrinth reflexes have been analysed in cranial muscles of healthy man. The frontalis and orbicularis oculi (pars orbitalis) muscles are the site of positional reflexes of cervical origin, which are involved in the control of eyelid position during head movements. At a mandibular level, postural influences are set up in the masseter and digastric muscles upon ventral and dorsal flexion of the head. Their reciprocal character contrasts with the lack of evidence concerning reciprocal proprioceptive jaw reflexes. The genioglossal muscle is the site of an intense postural activity when the head is flexed dorsally. The latter influences appear related to the preservation of free air passage to the lungs.
Adult↗
Postural uncertainty leads to dynamic control of cutaneous reflexes from the foot during human walking.
Cutaneous reflexes evoked by stimulation of nerves innervating the foot are modulated in a phase-dependent manner during locomotion. The pattern of modulation of these reflexes has been suggested to indicate a functional role of cutaneous reflexes in assisting to maintain stability during walking. We hypothesized that if cutaneous reflexes assist in maintaining stability during gait, then these reflexes should be modulated in a context-dependent manner when subjects are asked to walk in an environment in which stability is challenged. To do this, we asked subjects to walk on a treadmill under five conditions: (1) normally, (2) with the arms crossed, (3) while receiving unpredictable anterior-posterior (AP) perturbations, (4) with the arms crossed while receiving unpredictable AP perturbations, and (5) with the hands holding onto fixed handles. Cutaneous reflexes arising from electrical stimulation of the superficial peroneal (SP; relevant to stumbling) or distal tibial (TIB; relevant to ground contact sensation) nerves were recorded bilaterally, at four points in the step cycle. Reflexes evoked with SP nerve stimulation showed marked facilitation during the most unstable walking condition in 4 of the 7 muscles tested. SP nerve-evoked reflexes in the muscles of the contralateral leg also showed suppression during the most stable walking condition. Reflexes evoked with TIB nerve stimulation were less affected by changes in the walking task. We argue that the specific adaptation of cutaneous reflexes observed with SP nerve stimulation supports the hypothesis that cutaneous reflexes from the foot contribute to the maintenance of stability during walking.
Adult↗
Afferent mechanisms for the reflex response to imposed ankle movement in chronic spinal cord injury.
We have reported earlier that externally imposed ankle movements trigger ankle and hip flexion reflexes in individuals with spinal cord injury (SCI). In order to examine the afferent mechanisms underlying these movement-triggered reflexes, controlled ankle movements were imposed in 17 SCI subjects. In 13 of these subjects, reflex torques were recorded at the hip, knee and ankle in response to 5 ankle movement ranges, and 4 movement speeds. Subjects were tested using both ankle plantarflexion and dorsiflexion movements. The principal outcome measure, peak hip flexion torque of the induced reflexes, was used for comparing the effects of movement range and speed on the reflex response. We found that movement-triggered reflexes were sensitive to the angular range of ankle deflection, but insensitive to the velocity of the movement. Movement amplitudes sufficient to trigger hip and ankle flexion were routinely associated with increases in ankle passive force, suggesting that force-sensitive receptors participated in the reflex response. However, increases in angular range also corresponded to increases in muscle length, making it difficult to distinguish whether the response was triggered by a load-sensitive receptor (e.g., Golgi tendon organ or muscle free nerve ending) or a position-sensitive receptor responsive to absolute ankle angle (e.g., muscle spindle secondary afferent). The absence of velocity dependence of the reflex suggested that spindle Ia afferents were not major contributors. These results suggest movement-triggered reflexes originate in muscle receptors that are sensitive to either absolute muscle length, to muscle force or to both. Although receptors that are sensitive to absolute muscle length cannot be excluded with certainty, the finding that reflex responses require that ankle movements elicit an increase in passive force argues for a prominent role of nonspindle mechanoreceptors, such as group III/IV muscle afferents. These afferents are activated preferentially as muscles are stretched to near maximum length, and they appear to have potent reflex effects in spinal cord injury.
Adolescent↗
Control of upright standing posture during low-frequency linear oscillation.
We examined the effects of anteroposterior movement of a sled on human upright standing. Each of six healthy men stood on the platform of a sled in the dark. The sinusoidal acceleration was provided, from 0.02 to 0.04 G, followed by 0.06 and 0.08 G, at a stroke length from 6 to 10 m and then to 14 m. Low acceleration (0.02 and 0.04 G) induced body sway, pivoting on the ankle joint. High acceleration (0.06 and 0.08 G) increased body sway, but the head-neck joint remained locked upright. The electromyographic recordings of the lower leg muscles revealed continuous tonic EMG activities of the gastrocnemius and tibialis anterior muscles at acceleration of 0.02 and 0.04 G, while reciprocal activation was observed at 0.06 and 0.08 G. During head movement, the neck muscles were slightly activated tonically at acceleration of 0.02 and 0.04 G, but they were markedly and tonically activated at 0.06 and 0.08 G. We speculate that the sled oscillation caused body sway in proportion to the acceleration, with the ankle joint playing a principal role. Analysis of neck movement also revealed that the head was held in a fixed upright position, indicating that the vestibulocollic reflex might tonically activate the neck muscles.
Acceleration↗
A biophysical approach to the spatial function of eye movements, extraocular proprioception and the vestibulo-ocular reflex.
The eyeball and the extraocular muscles are used as a paradigm to design a linear spatial model of a single joint with a redundant set of muscles. On the basis of this model relations are derived between orientation, torque, motor commands, and proprioceptive signals. These relations show that the tenet underlying the tensorial interpretation of neural signals in sensorimotor systems does not have general validity. A mechanism is proposed to show how proprioception may play a role in optimizing the coordination of muscles during spatial tasks. Further, a new concept is suggested that allows one to predict the neural connectivities mediating the redundant spatial vestibulo-ocular reflex. This concept has the advantage of minimizing both sensorial error and motor effort.
Biophysical Phenomena↗
Proprioceptive mechanisms in the cruciate ligaments: an electromyographic study on reflex activity in the thigh muscles.
The hypothesis of a proprioceptive mechanism arising from mechanoreceptors in the cruciate ligaments and with efferences to the thigh muscles is investigated in an animal model. Electromyographic (EMG) studies of the quadriceps and hamstrings muscles were performed in six sheep anesthetized by intravenous injection of chloralose on applying static and dynamic shear forces to isolated fascicle bundles in the anterior (ACL) and posterior (PCL) cruciate ligaments at 200 to 500 N and 50 to 200 N/sec, respectively. With the help of an external fixator, the knee joint position was varied at 25 to 150 degrees. The relative preload of the anteromedial and posterolateral fascicles in the ACL and the anterior and posterior fascicles in the PCL induced by variation of the joint angle was measured with the help of strain gages. By static and dynamic loading of the anteromedial group of the ACL, EMG activity in the hamstrings increases significantly to 159 +/- 22 and 257 +/- 46 microV seconds, respectively (p < 0.001), with a simultaneous suppression of the quadriceps activity. Static and dynamic loading of the posterolateral ACL group results in a significant excitation of the quadriceps with mean potentials of 142 +/- 29 and 173 +/- 23 microV seconds, respectively (p < 0.001). Mechanical shear applied both to the anterior and posterior fascicles of the PCL induces a significant activation of the ipsilateral quadriceps muscles with a simultaneous inhibition of the hamstrings (p < 0.001). The quality of mechanical loading, i.e., static or dynamic shear, determines the degree of muscular recruitment significantly (p < 0.01). The joint angle contributes to a modulation in the quantitative EMG excitation. Linear regression analysis of the integrated EMG potential values and the amount of passive preload induced by the respective joint position results in a close correlation (r = + 0.78 to + 0.86). The results lead to the conclusion that a proprioceptive mechanism exists that arises from the cruciate ligaments and influences the tone in the thigh muscles. The degree of muscle excitation on mechanical ligament loading is modulated by the amount of preload in the ACL and PCL and the quality of load applied.
Animals↗
Exteroceptive suppression of masseter muscle activity in juvenile migraineurs.
The second exteroceptive suppression period (ES2) of masseter or temporalis muscle activity may be reduced in adults with chronic tension-type headache. In adults with migraine, ES2 was found normal or tended to be protracted. To date, no studies on exteroceptive suppression in children and adolescents with headaches have been published. We investigated the exteroceptive suppression of masseter muscle activity in 14 migraineurs and 19 controls between 6 and 18 years of age. It was elicited by electrical stimulation at the labial commissure. No differences were found regarding the first suppression period, but ES2 was significantly longer in the migraine group than in controls. The results of the migraine group suggest overactivity of the interneurons of the reflex loop due to impaired inhibitory control from superior antinociceptive systems already at the beginning of this headache disorder.
Adolescent↗
The spinal frog takes into account the scheme of its body during the wiping reflex.
The hindlimb of the spinal frog produces a wiping reflex evoked by electrically or chemically stimulating distal skin of the forelimb. The reflex was released in frogs supported on a flat surface or suspended. It was found to have two stages. During the first, the frog fixed the hindlimb in an intermediate posture irrespective of forelimb position. In the second, the movement depended on forelimb position, which determined the final posture of the hindlimb. In this final posure, all joints except the hip joint were fully extended; the hip angle was correlated with forelimb position and varied on repeated wipings. When the stimulus was applied to the skin of the back, the pattern of final postures was the same, but the intermediate postures differed. The organization of the wiping reflex is discussed in light of the hypothesis that movement is evoked according to changes in the equilibrium (postural state) of the system.
Animals↗
Influences on blink reflex induced by IA afferents in human subjects.
The effects induced by IA volleys, evoked with H reflex, on the blink reflex elicited upon electric activation of supraorbital nerves were investigated in 14 healthy subjects as well as in 4 cerebrovascular patients. In both groups a significant increase in amplitude of the early component (R1) of ipsilateral blink reflex has been observed. A brief discussion of possible neural systems which might be involved in these effects is given.
Blinking↗
[Clinico-electrophysiologic studies of the spastic syndrome and its neurosurgical treatment in patients with spinal cord lesions].
The authors analyse the results of surgical treatment of spastics in 15 patients with spinal cord lesions. The results of a dynamic, neurological and electrophysiological examinations permit to draw several conclusions on the mechanisms of spasticity and its elimination by surgery. A restoration of reflex activity in the absence of the spastic syndrome is considered by the authors as a favourable result of the operation.
Electromyography↗
Sensory pathways and their modulation in the control of locomotion.
Recent experiments have extended our understanding of how sensory information in premotor networks controlling motor output is processed during locomotion, and at what level the efficacy of specific sensory-motor pathways is determined. Phasic presynaptic inhibition of sensory transmission combined with postsynaptic alterations of excitatory and inhibitory synaptic transmission from interneurons of the premotor networks contribute to the modulation of reflex pathways and to the generation of reflex reversal. These mechanisms play an important role in adapting the operation of central networks to external demands and thus help optimize sensory-motor integration.
Animals↗