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PubMed2004

Sensing the effect of body load in legs: responses of tibial campaniform sensilla to forces applied to the thorax in freely standing cockroaches.

Sense organs in the legs that detect body weight are an important component in the regulation of posture and locomotion. We tested the abilities of tibial campaniform sensilla, receptors that can monitor forces in the cockroach leg, to encode variations in body load in freely standing animals. Small magnets were attached to the thorax and currents were applied to a coil below the substrate. Sensory and motor activities were monitored neurographically. The tibial sensilla could show vigorous discharges to changing forces when animals stood upon their legs and actively supported the body weight. Firing of individual afferents depended upon the orientation of the receptor's cuticular cap: proximal sensilla (oriented perpendicular to the leg axis) discharged to force increases while distal receptors (parallel to the leg) fired to decreasing forces. Proximal sensillum discharges were prolonged and could encode the level of load when increases were sustained. Firing of the trochanteral extensor motoneuron was also strongly modulated by changing load. In some postures, sensillum discharges paralleled changes in motor frequency consistent with a known interjoint reflex. These findings demonstrate that tibial campaniform sensilla can monitor the effects of body weight upon the legs and may aid in generating support of body load.

Animals↗

PubMed1992

[The discal system of the temporo-mandibular junction].

The discal apparatus represent the intra-articular part of the lateral pterygoid muscle tendon, which is differentiated in front of articular surfaces. It is involved in craniomandibular shock absorbing, joint proprioception, and also plays an important part in both condylar growth and morphogenesis. This is to emphasize the different roles of this apparatus, which should be religiously preserved, its lesions being, most of the time, irreversible and cause of TMJ disorders.

Humans↗

PubMed2002

The effect of aging on dynamic position sense at the ankle.

The present study addressed whether dynamic position sense at the ankle--or sense of position and velocity during movement--shows a similar decline as a result of aging as previously described for static position sense and movement detection threshold. Additionally, the involvement of muscle spindle afferents in the possible age-related decline was studied. To assess dynamic position sense, blindfolded subjects had to open the hand briskly when the right ankle was rotating passively through a prescribed target angle. To assess the involvement of muscle spindles, the effect of tibialis anterior vibration was studied. The results showed that aging lead to a significant increase in deviation from the target angle at hand opening as well as in variability of performance. Vibration resulted in larger undershoot errors in the elderly compared to the young adults, suggesting that the age-related decline in performance on the dynamic position sense task is not (solely) due to muscle spindle function changes. Alternatively, this degeneration might be due to altered input from other sources of proprioceptive input, such as skin receptors. The elderly subjects did show a beneficial effect of practice with the task, which may provide solid fundaments for rehabilitation.

Adult↗

PubMed1995

Motor reactions and vestibular reflexes in cats and monkey in weightlessness.

Close morpho-functional relationships of the cerebellum and vestibular system at all stages of phylogenesis of vertebrates suggest that cerebellum can be regarded as an important center of gravireceptive function. Direct examination of electrical activity of the labyrinth in cats during transient (1-2 sec) state of weightlessness produced by free fall has shown that there was an almost two fold increase in both the rate and amplitude of electrical activity in the vestibular ganglion. It is commonly accepted at present time that the conditions of orbital flight around Earth closely connect with weightlessness that usually manifests itself as undesirable factor of flight. It is known, that vestibular, proprioceptive, visual and other sensory modalities are converted on the cerebellum, which would indicate that this information is used for motor coordination and spatial orientation. Undoubtedly, origin of many vestibulo-motor disturbances during flight and in postflight period to a considerable degree depends on weightlessness. On the whole the visual illusions, motor discoordination, and space sickness, including vomiting are referred to the "space adaptation syndrome." But nature of these disturbances still is not well understood. This investigation was dedicated to study of vestibular and motor reactions of cats and monkey in short-term microgravity.

Animals↗

PubMed2003

Physiology of the eyelid motor system.

The eyelid motor system represents an excellent experimental model for the study of reflex and learned motor responses. Eyelid responses can be recorded quantitatively with the search coil in a magnetic-field technique. Stimuli able to evoke reflex blinks (air puffs, flashes of light, tones) can also be controlled quantitatively. Eyelid movements can be classified as spontaneous, passive (such as those following eye saccades), reflex, and acquired with classical conditioning procedures. Information is available regarding the firing activity of brainstem motoneuronal pools (abducens, accessory abducens, and facial motoneurons) involved in these types of eyelid response. In particular, facial motoneurons present different encoding properties for the generation of reflex against learned eyelid responses. In cats, accessory abducens motoneurons are involved only in reflex (but not in learned) blinks. The recent description of the complete organization of premotoneuronal pathways related to eyelid motorics opens new experimental possibilities for the study of this particular motor system.

Abducens Nerve↗

PubMed2002

Sensory contributions to the control of stance: a posture control model.

We present the outline of a dual kinetic-kinematic postural control model. It is based on concepts of inter-sensory interaction (sensor fusion) which we consider instrumental for sensorimotor integration. Separation into kinetic and kinematic control signals begins at the level of the sensors (e.g., vestibular system--otoliths: force field meters, canals: head angular speedometers). Sensor fusion mechanisms are used to yield separate internal representations for foot support kinematics, force fields such as gravity, and contact forces such as pull or push having impact on the body. These representations are fed as global set point signals into local proprioceptive control loops of the joints. Fed into an ankle joint proprioceptive loop for body-on-support stabilization, they yield compensation of support tilt, gravity and contact forces, even when these stimuli are combined and, furthermore, voluntary lean is superimposed. Model simulations parallel our experimental findings so far obtained.

Animals↗

PubMed1985

Motor behavior underlying the control of an upside-down vertical posture.

The present study examines the control of equilibrium by trained acrobats standing balanced upside-down on their hands. The focus of the experiment was to analyze the postural attitudes of various body segments and the underlying motor activity, and to evaluate the influence of vision. We found a strong correlation between the motor activity of two antagonist muscles of the forearm and the anteriorposterior position of the center of gravity. The upside-down standing posture was most stable when the neck was dorsiflexed, indicating that the tonic neck reflex and the tonic labyrinthine reflex play an important role in the stability of this posture. Comparison between known data about the normal standing posture, on the feet, and the upside-down standing posture, on the hands, shows that motor behavior of the two postures is similarly organized.

Electromyography↗

PubMed1991

Autonomic peripheral evoked potential (APEP): a non-invasive procedure to assess sympathetic responses in humans.

The present study describes skin potential responses during a sequence of extero-, intero- and proprioceptive stimuli in 73 normal human subjects. By plotting the first derivative of skin potential vs. skin potential changes for every stimulus (phase plane) a generally opposite behavior of positive and negative deflections (indicating sympathetic inhibition and activation, respectively) was found. By area subtraction in phase plane analysis, only olfactory stimulation or nasal hyperventilation exhibited a significantly negative (sympathetic activating) skin potential response. Frequency of positive (sympathetic inhibitory) fluctuations of first derivative of skin potential was significantly lower than basal after explosive sound, tactile discrimination, photomotor reflex, and nasal and oral hyperventilation. Frequency of negative (sympathetic activating) fluctuations augmented significantly (as compared to basal) after explosive sound, tactile discrimination, nasal or oral hyperventilation, upright position or trot. These results suggest that activation of the sympathetic nervous system involves a coordinated motor program comprising activation of certain areas, and inhibition (or lack of changes) in others, with different patterns of interrelated activation and inhibition depending upon stimulus.

Adolescent↗

PubMed1979

Neurological development of kittens.

The neurological development of the kitten was studied from birth to 120 days of age. Three motor features present at birth disappeared within the 1st 45 days of life. The labyrinthine head and body righting reactions were present at birth; the latter matured only by 25 days of age when the air righting reaction (mature by 35 days) started to appear. Limb placing reactions developed progressively with proprioceptive components being present at birth whereas tactile components evolved slowly from early contact lifting to forepaws contact placing (60 days) and narrow plank walking (75 days). Standing and walking were well developed by 45 days. Eye opening occurred at 9.5 days and several eyeblink reactions (including blink to light) were present at birth. Adequate binocular coordination was seen by 47 days. Vision progressed parallel to the clearing of the ocular media which were fairly transparent by 32 days. Visually guided paw placing and the visuopalpebral blink reflex matured later (by 37 and 59 days, respectively). The external auditory canal and pinna were fully developed by 12 and 31 days, respectively; spontaneous and tactile pinna movements were present at birth; orienting to animal and nonanimal sounds was well developed by 6.5 and 18 days, respectively; spatial sound localization was developed by 16 days and differential responding to animal sounds matured by 24.5 days. Somatic responses and olfaction were present at birth but matured further thereafter. Playful interactions between kittens started by 10--15 days and well developed play behavior was seen by 36--40 days. In brief, all neurological functions mature progressively during the 1st 3 postnatal months.

Animals↗

PubMed1996

Reconstruction of the anterior cruciate ligament with a cyropreserved ACL allograft. A microangiographic and immunohistochemical study in rabbits.

The ACL in the rabbit is innervated by three types of nerve fibres. These subserve vasoconstriction, nociceptive and proprioceptive purposes. The aim of this paper was to investigate the revascularisation and reinnervation of cyropreserved ACL allografts in 22 New Zealand white rabbits. Cyropreserved grafts were used as they may excite less host immune response. Both microangiographic and immunohistochemical methods were used. We found that cryopreserved allografts exhibited little immune response, revascularisation was considerable by the 24th postoperative week and reinnervation was essentially complete by then. No mechanoreceptors were found in ACL allografts. In rabbits, the anatomical basis for the participation of ACL allografts in sensorimotor reflexes is not given before the twelfth week after transplantation.

Animals↗

PubMed2006

Comparison between stabilometry with and without head tilts in a roll plane.

OBJECTIVE: We examined the influence of head-tilting on stabilometry, which is similar to positional nystagmus in a sitting position. METHODS: The subjects were 35 healthy individuals and 11 patients with unilateral vestibular disorder. We compared parameters measured in an upright position and those with left head-tilt or right head-tilt. We used Wilcoxon's signed ranks test for statistical analysis. RESULTS: In the group of healthy adults, the Enveloped area with left head-tilt and right head-tilt increased significantly compared to that in the upright position (P=0.0111). The parameters that decreased significantly were Locus length per unit area (P=0.0007). The center of gravity on the Y-axis shifted backward significantly (P<0.0001). In the group of unilateral vestibular disorder, there were no parameters that showed significant difference CONCLUSION: One could argue that a combination of displacement of the body itself, influence of proprioceptive sensation, and influence of otolith affects the output of stabilometry. It would be possible to develop this test if the first and the second are excluded.

Adult↗

PubMed1978

Surgical treatment of spasticity in cerebral palsy.

Since 1971, we have surgically treated spasticity in 109 cases of cerebral palsy with posterior rhizotomy. The best results have been obtained with functional posterior rhizotomy, an original modification of Foerster's technique, in which the selection of the roots/rootlets to be sectioned is based on functional exploration of the spinal circuits involved in the maintenance of spasticity, using intraoperative electrostimulation on dorsal roots. This method makes selective sections possible, thereby saving a larger number of normal proprioceptive afferents, with consequent reduction in negative side effects. No recurrencies have been observed in our 3-year follow-up. The main indication is Little's disease.

Cerebral Palsy↗

PubMed1994

Contribution of neuromuscular impairment to physical functional status in patients with lumbar spinal stenosis.

OBJECTIVE: To evaluate the relationship between neuromuscular impairment and physical functional status in patients with lumbar spinal stenosis. METHODS: Cross sectional analysis of 217 consecutive patients with lumbar spinal stenosis referred to 3 teaching hospitals. Physical functional status was measured with the physical dimension of the Sickness Impact Profile (P-SIP). Physical and radiological findings were abstracted from clinical records. The neuromuscular findings included pin sensation, strength, deep tendon reflexes and vibration. They were aggregated in a neuromuscular impairment index (NMI). Univariate relationships of the P-SIP and the NMI were analyzed with nonparametric methods. The determinants of physical functional status were evaluated using multiple linear regression models. RESULTS: In 148 patients with complete clinical data, objective weakness of the lower extremity as measured at rest was not related to physical functional status in univariate analyses. Decreased vibration was common and was associated with balance disturbance and reduced physical functional status, reflecting the importance of proprioception loss. In the multivariate regression analysis, neuromuscular deficit explained only 2.5% of the variance in physical functional status. The primary determinants of physical functional status were pain, depression, comorbid conditions and work status. CONCLUSION: While neuromuscular impairment is an indispensable feature of the diagnostic evaluation, its value in assessing outcome is limited. The decision whether to intervene surgically in patients without cauda equina syndrome or rapidly progressive neurological deficits should therefore be driven by pain and physical disability rather than the degree of neuromuscular impairment.

Aged↗

PubMedDate not supplied

Diffuse noxious inhibitory controls (DNIC) in animals and in man.

Some neurones in the dorsal horn of the spinal cord are strongly inhibited when a nociceptive stimulus is applied to any part of the body, distinct from their excitatory receptive fields. This phenomenon was termed "Diffuse Noxious Inhibitory Controls" (DNIC). DNIC influence only convergent neurones: the other cell types which are found in the dorsal horn, including specific nociceptive neurones, are not affected by this type of control. In normal conditions, these inhibitions can be triggered only by conditioning stimuli which are nociceptive. The inhibitions are then extremely potent, affect all the activities of the convergent neurones and persist, sometimes for several minutes, after the removal of the conditioning stimulus. In fact, only activity of A delta- or A delta- and C-peripheral fibres can trigger DNIC. DNIC are sustained by a complex loop which involves supraspinal structures since, unlike segmental inhibitions, they can not be observed in animals in which the cord has previously been transsected at the cervical level. The ascending and descending limbs of this loop travel respectively through the ventro-lateral and dorso-lateral funiculi respectively. We proposed that DNIC result from the physiological activation of some brain structures putatively involved in descending inhibition. However, lesions of the following structures did not modify DNIC: Periaqueductal grey (PAG), Cuneiform nucleus, Parabrachial area, locus coeruleus/subcoeruleus, rostral ventromedial medulla (RVM) including Raphe Magnus, Gigantocellularis and Paragigantocellularis nuclei. By contrast, lesions of Subnucleus Reticularis Dorsalis (SPD) in the caudal medulla strongly reduced DNIC. Both electrophysiological and anatomical data support the involvement of SRD neurones in spin-bulbo-spinal loop(s). Indeed, they are unresponsive to visual, auditory or proprioceptive stimulation but are preferentially or exclusively activated by nociceptive stimuli with a "whole-body receptive field"; they encode precisely the intensity of cutaneous and visceral stimulation within the noxious range and are exclusively activated by cutaneous A delta- or A delta- and C-fibre peripheral volleys; they send descending projections through the dorsolateral funiculus that terminate in the dorsal horn at all levels of the spinal cord. In man, exactly analogous results have been obtained by means of combined psychophysical measurements and recordings of nociceptive reflexes. Electrical stimulation of the sural nerve at the ankle simultaneously induces a nociceptive reflex in a flexor muscle of the knee (the RIII reflex) and a painful sensation from the territory of the nerve. Painful heterotopic conditioning stimuli, no matter whether thermal, mechanical or chemical in nature, depress both the reflex and the associated painful sensation, with stronger effects being observed with more intense conditioning stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2002

Treating vertigo with vestibular rehabilitation: results in 155 patients.

Balance is fundamental to our daily activities and the vestibular system, together with vision and proprioceptive functions, are the main structures involved in this process. Dizziness is the main clinical manifestation of malfunction of these systems. The mechanisms of vestibular compensation are one of the most studied aspects since they play an important role in the patient's everyday activities. In this retrospective description of a series of cases the authors present their results in 155 patients that underwent a program of vestibular rehabilitation (VR). The program, first described by Cawthorne and Coosey, is based on mechanisms of potentiation of the cervico-ocular reflex and substitution of the lost vestibular cues for visual and somatosensory cues. The results were satisfactory (remission or partial cure) in 75.5% of the patients, with an average treatment time of up to 2 months and 5 or fewer sessions performed in most of the cases. The results were somewhat inferior in those cases in which a central vestibular lesion or more than one etiologic factor was present. The results of a subgroup of elderly patients (age > 65 years) were similar to those of the total number of studied subjects. Vestibular rehabilitation, associated to the specific etiological treatment, appears to be a very useful tool in the management of patients suffering from dizziness of all ages, although different clinical responses to the therapy may vary according to the presence of a central or a peripheral vestibular lesion or multiple etiological factors.

Adolescent↗

PubMed1984

Mathematical modeling and simulation of the postural control loop. Part III.

The engineering analysis and modeling of the neuromuscular system is an exciting and challenging area of research where we may learn something about the principles of controlling large, complex systems. This review is limited to the most peripheral subsystem: the postural control loop. In the first part, we reviewed the input-output properties of the motoneuron pool, modeling of the motor unit action potential, and analysis of the interference electromyographic activity. Aslo included were the engineering techniques to quantitatively study electromyographic activity and its relationship to muscle force. The second part of this review focuses on the biomechanical models of the muscle based on Hill's work as well as the modern sliding filament theory. This section also includes models of the proprioceptive receptors: the muscle spindle organ and the Golgi tendon organ. In this final paper we discuss various models and simulations of the peripheral loop and their applications to study physiological system behavior such as tremor.

Afferent Pathways↗

PubMed1998

Distribution of muscle spindles in a simply structured muscle: integrated total sensory representation.

BACKGROUND: The distribution of muscle spindles (Sps) in a small muscle of simple architecture, the capsularis at the cat's hip joint, was quantified to reveal the patterns of proprioceptive representation in the transverse and sagittal planes as well as to model the effect a local disturbance in muscle length would have on total Sp discharge. METHODS: Locations in serial cross-sections of the 32 and 38 Sps in 2 muscles, 1 perfused with the hip joint flexed and the other extended, were plotted, and their patterns of integrated sensitivity calculated assuming that (1) the discharge rate of a Sp afferent varies linearly with change in length along the Sp's axis, and (2) that within a local disturbance produced by contraction of a motor unit (MU), lengths decrease either linearly or as the square of the distance from its center. RESULTS: The isomeric pattern of "integrated, total Sp representation on cross-section" showed two peaks of sensitivity in the half of the muscle that had been next to the joint capsule, offset by low representation in a small, central area and along the extensive zone bordering the laterally facing "superficial surface." The equivalent radius of an idealized symmetrical MU territory was estimated from distributions of the few fast, oxidative-glycolytic fibers found in two muscles, and the effect of a MU's contraction on net Sp discharge predicted when the unit was positioned at distinctive sites within the pattern. As an index of Ia and II afferent representation in the sagittal plane, the distribution of the nucleated regions of Sps and the summed lengths of segments of Sp axial bundles and capsules, respectively, within successive 1-mm segments of the muscle were graphed. CONCLUSIONS: The longitudinal representation and structure of the muscle are not suited for reflex adjustment of differences in length along the muscle. The isomeric pattern of high relief in the transverse plane suggests that in this approximately 0.2 g muscle, the localization of myotatic reflexes might be accommodated but the need for adjustment in activation of MUs seems minimal. This is because the muscle is not compartmentalized, its fibers extend between the muscle's origin and insertion, their angle of pinnation is low, and greater than 90% are of slow type. The distribution of Sps is consistent with gauging length of the entire muscle and hence angulation at the hip joint.

Animals↗

PubMed1995

A simple technique to measure body sway in normal subjects and patients with dizziness.

For many years vestibular testing has relied on measurements of the vestibulo-ocular reflex (VOR). More recently quantified assessment of balance, using fixed or moving force platforms and magnetometry have been applied to clinical research. These are objective attempts to quantify the vestibulospinal reflex (VSR). This study evaluates whether SwayWeigh, a simple device which measures lateral body sway, can provide an objective assessment of balance dysfunction. Forty patients with a balance disorder and 31 subjects with normal balance were tested with eyes opened and eyes closed whilst they were standing on a flat surface and then on an air bed. The lateral sway in patients with a balance disorder was compared to that in the normal subjects and highly significant differences (p < 0.0001) were observed. The results also confirmed the importance of vision and proprioception in the maintenance of posture. The SwayWeigh balance platform is a simple and economical device which objectively measures balance dysfunction.

Adult↗