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Results for “REFLEX, PROPRIOCEPTIVE”

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At least 379 records · Page 21Linked to original sources
PubMed1986

Cervico-vestibular interaction in eye movements.

The cervico-vestibular interaction was investigated in normal subjects and patients with unilateral labyrinthine dysfunction using neck vibratory stimulation and caloric stimulation. There is a functional interaction between sensory inputs from the neck proprioceptors and the peripheral labyrinth in the patients with unilateral labyrinthine dysfunction. However, this interaction was not observed in normal subjects. This result indicates that the role of the cervical sensory inputs in normal subjects and the patients is different. That is, inputs from the neck proprioceptors have little effect on the control of eye movements in normal subjects, whereas the neck inputs are quite important for the control of eye movements in patients with unilateral labyrinthine dysfunction.

Afferent Pathways↗
PubMed1992

Assessment of the nervous system.

This article describes the examination of the neurologic and ophthalmic systems in ruminants. Neuroanatomy with respect to lesion localization is reviewed. Pertinent age and species differences are addressed. The practical aspects of assessing the neurologic system are stressed, and the reader is directed to other sources of information for assistance in determining the differential diagnosis and therapy of neurologic disease.

Animals↗
PubMedDate not supplied

[Proprioceptive regulation of standing in the human. An electromyography study].

Electromyographic experiments, undertaken in connection with action of standing, are here described. A short, sharp push given in an anterior or posterior direction caused an abrupt upsetting of balance, whereby adaptive reactions of the relevant muscles were found to occur after an interval of 60 to 90 msecs. These reactions, although having become automatic as a result of the early-acquired upright posture, are in fact of a voluntary nature and fully controllable by the will. It is demonstrated that these reactions are very probably due to stimulation of deep mechano- and joint-receptors. They do not have anything to do with a functional stretchreflex mechanism.

Adult↗
PubMed1981

A progressive neurologic syndrome in children with chronic liver disease.

A progressive neurologic syndrome developed in six children with longstanding cholestatic liver disease. The neurologic abnormalities included areflexia, gait disturbance, decreased proprioceptive and vibratory sensation, and paresis of gaze. Serum vitamin E concentrations were uniformly low. Neuropathological studies carried out in two of the three fatal cases revealed degeneration of the posterior column, selective loss of large-caliber, myelinated axons in peripheral nerve, and spheroids in the gracile and cuneate nuclei. These lesions are similar to those found in animals with experimentally induced vitamin E deficiency. We therefore speculate that the neurologic syndrome in these children may be the result of chronic vitamin E malabsorption.

Adolescent↗
PubMed2000

Dizziness in discus throwers is related to motion sickness generated while spinning.

While both discus and hammer throwing involve rotating movements resulting in the throw of an object, discus throwers sometimes report dizziness, a condition never experienced by hammer throwers. We investigated whether this susceptibility was related to the sensitivity of the thrower or to the type of throwing achieved. For the latter, we compared the determining features of gesture, gaze stabilization and projectile trajectory in both sports. A total of 22 high-level sportsmen in these 2 disciplines, half of them practising both sports, were interviewed. Slow motion video recordings of discus and hammer throwing were examined to determine the visual referential, head movements and plantar surface support area involved at each stage of the motions. Discomfort was reported by 59% of the sportsmen while throwing discus, but by none while throwing hammer. Because several individuals practised both sports, these results exclude the hypothesis of individual susceptibility to dizziness. Video analysis evidenced that during hammer throwing, visual bearings can be used more easily than during discus throwing. Moreover, there is a loss of plantar afferents and generation of head movements liable to induce motion sickness, such as Coriolis acceleration. In conclusion, although hammer and discus-throwing present numerous similarities, we demonstrate here that crucial differences in the specific execution of each sport are responsible for the dizziness experienced by discus throwers.

Adult↗
PubMed1994

Generalised ceroid-lipofuscinosis and brown bowel syndrome in Cocker spaniel dogs.

The ceroid-lipofuscinoses comprise a group of inherited storage diseases of human beings and animals that are characterised by progressive neurodegenerative disease and the accumulation within cells of a fluorescent lipopigment. A distinct syndrome occurs in Cocker spaniel dogs in which there is a generalised accumulation of a lipofuscin-like pigment, with such a heavy accumulation in smooth muscle that the intestine and other organs have a brown discolouration. Such discolouration is not observed in other forms of ceroid-lipofuscinosis. Dogs are clinically affected in adulthood and show progressive hind limb paresis, incoordination, and deficient postural reactions and proprioception. Spinal reflexes may be exaggerated. Behavioural or temperament changes, seizures or blindness may occur.

Journal Article↗
PubMed2005

Visual perception and interception of falling objects: a review of evidence for an internal model of gravity.

Prevailing views on how we time the interception of a moving object assume that the visual inputs are informationally sufficient to estimate the time-to-contact from the object's kinematics. However, there are limitations in the visual system that raise questions about the general validity of these theories. Most notably, vision is poorly sensitive to arbitrary accelerations. How then does the brain deal with the motion of objects accelerated by Earth's gravity? Here we review evidence in favor of the view that the brain makes the best estimate about target motion based on visually measured kinematics and an a priori guess about the causes of motion. According to this theory, a predictive model is used to extrapolate time-to-contact from the expected kinetics in the Earth's gravitational field.

Adaptation, Physiological↗
PubMed2005

An optimal state estimation model of sensory integration in human postural balance.

We propose a model for human postural balance, combining state feedback control with optimal state estimation. State estimation uses an internal model of body and sensor dynamics to process sensor information and determine body orientation. Three sensory modalities are modeled: joint proprioception, vestibular organs in the inner ear, and vision. These are mated with a two degree-of-freedom model of body dynamics in the sagittal plane. Linear quadratic optimal control is used to design state feedback and estimation gains. Nine free parameters define the control objective and the signal-to-noise ratios of the sensors. The model predicts statistical properties of human sway in terms of covariance of ankle and hip motion. These predictions are compared with normal human responses to alterations in sensory conditions. With a single parameter set, the model successfully reproduces the general nature of postural motion as a function of sensory environment. Parameter variations reveal that the model is highly robust under normal sensory conditions, but not when two or more sensors are inaccurate. This behavior is similar to that of normal human subjects. We propose that age-related sensory changes may be modeled with decreased signal-to-noise ratios, and compare the model's behavior with degraded sensors against experimental measurements from older adults. We also examine removal of the model's vestibular sense, which leads to instability similar to that observed in bilateral vestibular loss subjects. The model may be useful for predicting which sensors are most critical for balance, and how much they can deteriorate before posture becomes unstable.

Brain↗
PubMed2005

Internal models of limb dynamics and the encoding of limb state.

Studies of reaching suggest that humans adapt to novel arm dynamics by building internal models that transform planned sensory states of the limb, e.g., desired limb position and its derivatives, into motor commands, e.g., joint torques. Earlier work modeled this computation via a population of basis elements and used system identification techniques to estimate the tuning properties of the bases from the patterns of generalization. Here we hypothesized that the neural representation of planned sensory states in the internal model might resemble the signals from the peripheral sensors. These sensors normally encode the limb's actual sensory state in which movement errors occurred. We developed a set of equations based on properties of muscle spindles that estimated spindle discharge as a function of the limb's state during reaching and drawing of circles. We then implemented a simulation of a two-link arm that learned to move in various force fields using these spindle-like bases. The system produced a pattern of adaptation and generalization that accounted for a wide range of previously reported behavioral results. In particular, the bases showed gain-field interactions between encoding of limb position and velocity, very similar to the gain fields inferred from behavioral studies. The poor sensitivity of the bases to limb acceleration predicted behavioral results that were confirmed by experiment. We suggest that the internal model of limb dynamics is computed by the brain with neurons that encode the state of the limb in a manner similar to that expected of muscle spindle afferents.

Arm↗
PubMed1984

The use of hyperbaric oxygen to modify the effects of recent contusion injury to the spinal cord.

Studies on the experimental spinal contusion injury in animals confirm that posttraumatic ischemia contributes to central cystic necrosis or fibrosis occurring at the level of the spinal cord lesion. Hyperbaric oxygen (HBO) modifies the degree and extent of the pathology in the spinal cord of the experimental animals. HBO has been used for 45 patients with recent spinal cord injuries. The extent of recovery in 27 patients with upper motor neuron lesions treated with adequate HBO is reported. Fifteen of the 27 patients had useful functional recovery.

Adult↗
PubMed1994

Overpressure isoflurane at caesarean section: a study of arterial isoflurane concentrations.

In this study we have measured arterial concentrations of isoflurane obtained during Caesarean section in two groups of patients. Patients in group 1 received 1% isoflurane throughout operation, whilst those in group 2 received 2% isoflurane for the first 5 min, 1.5% for the next 5 min and 0.8% thereafter. We found that arterial isoflurane concentrations were significantly greater in group 2 than in group 1 (ANOVA, P < 0.05). Isoflurane concentrations greater than 30 micrograms ml-1 were achieved rapidly in most patients in both groups, but there was a large scatter of results. The isoflurane concentration at which awareness or recall may occur is not known, but an "overpressure" technique as described for patients in group 2 may result in fewer patients being at risk of awareness.

Adolescent↗