Orientation of the body response to galvanic stimulation as a function of the inter-vestibular imbalance.

We proposed to study and quantify the anteroposterior component, on top of the lateral one, of the body sway induced by different configurations of galvanic vestibular stimulation (GVS) in order to advance the understanding of the orientation of the response. Four stimulation configurations were used in two separate experiments: monaural, binaural, and opposite double monaural in the first experiment (11 subjects); monaural and double monaural in the second (13 subjects). The postural response of the subjects, standing with their eyes closed, to the stimulus (0.

Effect of galvanic vestibular stimulation on perception of subjective vertical in standing humans.

The present work reinvestigated the influence of bimastoidal galvanic vestibular stimulation (0.4 mA during 10 sec.) on subjective vertical.

Alteration of human cutaneous afferent discharges as the result of long-lasting vibration.

The unitary activities of slowly (15 SAI) and fast-adapting type I (12 FAI) skin mechanoreceptive afferent units innervating the anterior part of the human leg and foot were recorded by using the microneurographic method. The recordings were performed both at rest and on application of cutaneous stimuli of various intensities before and after exposure of the corresponding receptive fields to vibration (0.5 mm peak to peak, 100 pulses/s, 10 min).

Substance P-like immunoreactivity and analgesic effects of vibratory stimulation on patients suffering from chronic pain.

By applying vibratory stimulation to patients suffering from pain, it is possible to set up an inhibitory control on the pain pathways which is based on the activation of large-sized afferent fibres. The exact mechanisms responsible for these analgesic effects still remain to be determined, however. For this purpose, we investigated in the present study whether or not the analgesic effects were accompanied by a decrease in the CSF substance P-like immunoreactivity levels (SPLI) of seven patients suffering from chronic pain, who were fitted with a ventriculo-peritoneal drain.

[Transcutaneous mechanical vibrations: analgesic effect and antinociceptive mechanisms].

Although vibration has been used empirically for a long time in medicine, it was only about ten years ago that it began to be investigated scientifically. In the first part of this paper, we review the main data showing that vibratory stimulations can relieve both acute and chronic pain. In the second part, we consider the mechanisms responsible for the observed analgesic effects and discuss the nature of the sensory receptors involved and the effects of their activation on the triggering of central pain control systems.

[Met-enkephalin and substance P. Comparison of CSF levels in patients with chronic pain based on a sampling procedure].

The purpose of this study was to evaluate the Met-enkephalin and the SP-like immunoreactivity levels in the CSF of 16 patients suffering from chronic sciatalgia and to compare them with those of 8 control subjects. Eight of the patients had a ventriculo-peritoneal shunt which made it possible to collect samples of CSF painlessly. For the others patients and controls, CSF samples were collected by lumbar puncture.

Met-enkephalin and beta-endorphin are not involved in the analgesic action of transcutaneous vibratory stimulation.

Although the analgesic effects observed during the application of vibration may be attributable to neuronal inhibition of the pain pathways, this does not account for the fact that pain relief sometimes persists for a long time after the end of vibration treatment. Two experiments were carried out in order to determine whether pain relief might involve the release of endogenous opioids. In the first experiment, we studied the effects of injecting either a morphine antagonist, naloxone (0.

Analgesic effects of vibration and transcutaneous electrical nerve stimulation applied separately and simultaneously to patients with chronic pain.

The analgesic effects of transcutaneous electrical nerve stimulation (TENS) and vibratory stimulation (VS), used both separately and simultaneously, were compared in 24 patients suffering from chronic pain. We tested the hypothesis that these combined procedures might improve the pain reducing effects obtained with a single type of stimulation, since they make it possible to recruit a larger number of large diameter afferents and/or to increase the discharge frequencies. Four 35-minute treatment sessions (VS, TENS, VS + TENS, Sham stimulation) were run with each patient.

Post-contraction changes in human muscle spindle resting discharge and stretch sensitivity.

The activities of human muscle spindle primary endings were recorded in the lateral peroneal nerve using the microneurographic method. The aim of the study was to test whether voluntary isometric contraction causes any after-effects, first in the resting discharge of muscle spindle primary endings and secondly in their responses to a slow ramp stretch. To investigate the latter point, the initial angular position of the ankle was passively adjusted until the unit fell silent, in order to introduce a delay in the responses to muscle stretch.

Pain relief achieved by transcutaneous electrical nerve stimulation and/or vibratory stimulation in a case of painful legs and moving toes.

A patient is described with painful legs and moving toes. The pain had been occurring for more than 15 years, and a variety of therapies had been attempted with only partial, if any, success. Only morphine had succeeded in relieving the pain, but it had to be discontinued to avoid tolerance and dependence.

[Tendon vibrations as a tool for clinical investigation of the myotatic loop].

The degree of alteration of the myotatic loop was evaluated in 6 patients with polyradiculoneuropathy by studying deep reflexes and vibratory motor responses. The results showed that the reflex motor responses induced by vibration reappeared 2 to 4 weeks before the deep reflexes. Vibrations, therefore, could be a useful tool for the clinical follow-up of polyradiculoneuropathy.

Induction of illusory limb movement as a means of studying sensorimotor interactions in the eye-arm system.

In the present study, illusory movements were used as a means of investigating certain sensorimotor interactions: it was proposed to describe the effects produced on the oculomotor system when muscular proprioceptive afferents in the arm were artificially activated by tendon vibration. The gaze displacements induced by these vibratory stimuli were analyzed in terms of the instructions to subjects (i.e.

Forearm vs whole-body sensations of self-motion: some results on the role of the sensorimotor context.

Making a subject's visual surroundings move can give rise to sensations of self-motion, which can either be restricted to the arm or involve the whole body. The aim of the present study was to investigate the role played by the sensorimotor context in eliciting one or the other of these two types of illusory movement. Whether the type of sensation experienced by the subjects depended on their adoption of an actively maintained or relaxed posture was examined.

Interactions between visual and muscular information in illusions of limb movement.

The ability of visual and muscle-proprioceptive information to elicit simultaneous sensory illusions and motor responses has been utilized to study some interactions between these two types of kinesthetic information. The effects of double stimulation (visual and muscular) have been analyzed in terms of the sensations and EMG activities induced and compared to the effects of the same stimuli employed singly. The parameters manipulated concerned chiefly the conflicting or non-conflicting character of the double stimulations as well as their organization in time.

Perceptual and motor effects of agonist-antagonist muscle vibration in man.

Perceptual and motor effects of vibration applied simultaneously to the distal tendons of the Biceps and Triceps muscles, in isometric conditions and without sight of the stimulated arm, have been studied in human volunteers. Motor effects, measured by surface EMG, are inexistent when the flexor and extensor muscles are simultaneously vibrated at the same frequency. However, EMG activity appears in the muscle being vibrated at the lower frequency when simultaneous vibration is applied at different frequencies.

Perceptual and motor effects elicited by a moving visual stimulus below the forearm: an example of segmentary vection.

It has been shown in man that movement of a visual stimulus under the forearm may induce illusory sensations of movement (segmentary vection) and motor activity in the same direction, such that, for example, a sensation of elbow flexion is accompanied by EMG activity in biceps brachialis. The characteristics of these two types of activity, perceptual and motor, are analyzed and compared with analogous phenomena described for the whole body. These comparisons bring out two essential features: the effectiveness of stimuli of small surface area applied to central regions of the retina, and the non-compensatory character of the motor phenomena.

Demonstration of an illusory limb movement and associated motor activities induced by a moving visual stimulus in man. A descriptive study.

We show that, in man, a moving visual stimulus can induce sensations of movement of the forearm when it is exhibited beneath the hand and part of the forearm. These sensations in the limb are analagous to vection which has been described in the whole body. They are accompanied by involuntary motor activities coherent with the direction of illusory movement.

[Effects of vision on tonic vibration response of a muscle or its antagonists in normal man (author's transl)].

In normal man, a vibratory stimulus applied to tendon of arm muscles can induce either a tonic motor response in the vibrated muscle or in its antagonists depending upon presence or absence of visual feedback from arm (perception of position vrs. perception of an illusive motion). Spinal motor effects of inputs from muscle spindle afferents elicited by vibration can be modified by the perceptive events experienced by the subject.