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At least 1,297 records · Page 72Linked to original sources
PubMed1980

Human vestibulo-spinal responses to direct electrical eighth nerve stimulation.

Left-right (y-axis) vestibulo-spinal torque responses were recorded from two of four intramodiolar stimulus electrodes placed for auditory stimulation in one human subject. For both electrodes, shorter (100 msec) stimuli caused either subjective or objective head turning whereas stimuli lasting longer than 0.5 sec caused either subjective or objective body tilt depending upon the electrode stimulated. The two electrodes tested also showed strikingly different auditory and vestibular effects. Stimulation of the remaining two electrodes caused no detectable vestibulo-spinal responses.

Auditory Threshold↗
PubMed1984

Postural and oculomotor signs in labyrinthine-defective subjects.

Bilabyrinthless subjects, i.e. subjects clinically devoid of labyrinthine responses, show a greater than normal decrease in postural stability following eye closure. Because changes in head position, which affect posture in healthy subjects, do not do so in bilabyrinthless patients, static afferent information from healthy neck receptors does not contribute to postural stabilization. Somatosensory nystagmus and dynamic cervico-ocular responses are equally greater in bilabyrinthless than normal subjects, which indicates that both categories of eye movements are mediated by the same mechanism. Optokinetic nystagmus is slightly diminished in bilabyrinthless patients and optokinetic after-nystagmus was mostly absent. In terms of the Raphan-Cohen model our findings confirm that destruction of the labyrinthine function abolishes the vestibulo-ocular integrator function.

Ear, Inner↗
PubMedDate not supplied

Posturography findings in workers exposed to industrial solvents.

Postural control was investigated by static posturography in 18 workers exposed to industrial solvents, 9 patients with psycho-organic syndrome due to industrial solvent exposure, and 52 controls. Both groups of exposed subjects showed larger sway areas with eyes open as well as closed, compared with the controls. No differences were found in the Romberg quotient (the relationship between sway areas with eyes closed/open). The correlation between static posturography and the otoneurological test battery was positive for the visual suppression test in the styrene group. In the industrial solvent group no significant correlations were found. The visual suppression test and some auditory tests were pathological in the exposed groups. The otoneurological test battery--especially the visual suppression test and static posturography--seems to contribute in the assessment of solvent related CNS lesions.

Adult↗
PubMed1989

Neck-vestibular interaction in the vestibular nuclei. A dynamic, two-dimensional study.

In decerebrate cats we used response dynamics to classify neurons in Deiters' nucleus and the rostral descending nucleus as receiving input from vertical canals, otolith organs (utricle) or canal + otolith. Many of these neurons, particularly those with convergent vestibular input (canal + otolith, canal + canal) and preferred stimulus directions near roll, also received neck input. Neck and vestibular response vectors tended to point in opposite directions. Neck and vestibular response dynamics were often well matched, so that combined stimuli (head rotation) produced no response over a wide frequency range. In some cases differing dynamics produced an output that appeared to code head position.

Animals↗
PubMed1991

Ocular rotation and perception of the horizontal under static tilt conditions in patients without labyrinthine function.

In a previous study (1) it was found that in healthy subjects Ocular (Counter) Rotation is mainly due to otolith stimulation and only to a minor extent induced by slanted visual structures. Stimulation of the neck by tilting the trunk laterally upwards did not result in a systematic rotation of the eyes. In the present study it was found that subjects with bilateral loss of vestibular function showed a higher visually induced ocular rotation. Tilting the head (cervical stimulation) or the whole body (somatosensory stimulation) also led to a considerable OCR, demonstrating substitution of other sensory modalities for the loss of vestibular function. Estimates of the subjective horizontal were noisy, demonstrating the lack of an adequate gravitational reference signal.

Ear, Inner↗
PubMed1992

A new autosomal dominant syndrome of idiopathic progressive vestibulo-cochlear dysfunction with middle-age onset.

A kindred is described with progressive autosomal dominant vestibulo-cochlear dysfunction resulting in instability in the dark, head movement dependent oscillopsia and hearing loss. The first symptoms appeared in the 4th decade and progressed to vestibular areflexia, presumably in the 5th decade and to almost total deafness in the 6th-7th decade of life. The history was negative for other neurological, otological or infectious diseases, or the use of neuro-ototoxic drugs. The affected subjects showed remarkable compensation for the loss of vestibular function.

Aged↗
PubMed1993

Three-dimensional aspects of caloric nystagmus in humans: I. The influence of increased gravitoinertial force.

The influence of increased gravitoinertial force on the horizontal vertical and torsional components of caloric nystagmus response was examined. Video-oculographic (VOG) recordings were made on a group of 10 human subjects so that all three components of eye movement could be evaluated. The caloric nystagmus response at all tested g-levels included nystagmus components around all three rotation axes. Over the tested range of 1.0 g to 3.0 g, the results demonstrate that nystagmus intensity does not increase linearly with effective gravitoinertial force but appears to saturate at levels of 2.0 g and beyond. It is proposed that the vertical and torsional nystagmus components were elicited both by caloric stimulation to the (anterior) vertical canals and direct thermal mediation to the otolithic sensory cells. Vertical LZ-nystagmus response was also observed during centrifuge runs (previous to caloric irrigation) at all g-levels and in all subjects. The caloric-induced vertical nystagmus response was also clearly recognisable. The observation of a reduction and inversion of nystagmus intensity during g-transitions agrees with earlier findings and is attributable to the stimulation to the canals during centrifuge acceleration, respectively deceleration.

Caloric Tests↗
PubMed1994

Vestibular disturbance at frequencies above 1 Hz affects human postural control.

The effect of primary vestibular disturbance on postural control was investigated in 11 normal subjects exposed to perturbation by bi-polar binaural galvanic stimulation of the vestibular nerve. The stimulus consisted of 30 s of sinusoidal galvanic stimulation at a frequencies of 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0 Hz, with a current of +/- 1 mA, the subject standing with open or closed eyes, the response evoked being recorded with a force platform. As compared with resting values, i.e. no stimuli, variance of lateral body sway was significantly greater at all frequencies tested in the closed eyes condition and at frequencies of 0.2, 0.5, 1.0, 3.0 and 4.0 Hz in the open eyes condition; using a high pass filter with a cut-off frequency of 0.1 Hz, variance of lateral body sway was significantly greater at frequencies 0.2, 0.3, 0.5, 1.0 and 2.0 Hz in the closed eyes condition and at frequencies 0.5 and 2.0 Hz in the open eyes condition. These findings suggest that in the lateral plane vestibular input affects and probably contributes to human postural control over a wider frequency range than suggested by findings in previous studies. The trends in sagittal body sway were similar. Moreover, the visual contribution appears to enable the subject to suppress vestibular input causing lateral body sway only in the lower frequency range (here at 0.2 and 0.3 Hz), but with regard to the concomitant sagittal body sway at a much wider range of frequencies (here at all frequencies tested except 1.5 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Three-dimensional (3-D) eye movement analysis in patients with positioning nystagmus.

Benign paroxysmal positioning vertigo (BPPV), and nystagmus (BPPN) is the commonest type of rotational vertigo. Typical BPPN is generally believed to arise from one posterior semicircular canal. If this is true, the syndrome would offer the unique possibility to study vestibular responses when just one single semicircular canal is excited. In this study we used search coils to measure 3-D eye positions in 3 patients with BPPN. We present a complete 3-D description of the eye movements induced in BPPN. We found that in our patients the eyes rotate rather precisely in the plane of one posterior semicircular canal, suggesting that BPPN in our cases is indeed solely produced by the posterior semicircular canal.

Adult↗
PubMed1991

Interactions between automatic postural adjustments and anticipatory postural patterns accompanying voluntary movement.

In order to examine interactions between centrally initiated postural activity preceding voluntary arm movements and compensatory postural activity, we studied patterns of postural muscle activity preceding a vigorous bilateral reach and grasp task or triggered by support surface motion. The reaching task required movement onset to be coincident with a predictable stimulus, and in some trials a brief backward platform perturbation was timed to occur before, during, or after the reach onset. Centrally initiated anticipatory postural activity was subject-specific and was very often absent when perturbation-induced postural activity was elicited just prior to movement onset. Likewise, compensatory postural activity patterns elicited by the platform perturbation did not occur when they would have coincided with the anticipatory postural activity. These data support the idea that the central neural processes which determine the specific activation pattern of the supporting limb musculature are influenced by both the intended dynamic outcome and the current dynamic status of the body.

Adult↗
PubMedDate not supplied

Principal components analysis of an evaluation of the hemiplegic subject based on the Bobath approach.

An evaluation based on the Bobath approach to treatment has previously been developed and partially validated. The purpose of the present study was to verify the content validity of this evaluation with the use of a statistical approach known as principal components analysis. Thirty-eight hemiplegic subjects participated in the study. Analysis of the scores on each of six parameters (sensorium, active movements, muscle tone, reflex activity, postural reactions, and pain) was evaluated on three occasions across a 2-month period. Each time this produced three factors that contained 70% of the variation in the data set. The first component mainly reflected variations in mobility, the second mainly variations in muscle tone, and the third mainly variations in sensorium and pain. The results of such exploratory analysis highlight the fact that some of the parameters are not only important but also interrelated. These results seem to partially support the conceptual framework substantiating the Bobath approach to treatment.

Cerebrovascular Disorders↗
PubMed1981

Reversible brain-stem dysfunction following acute traumatic subdural hematoma: a clinical and electrophysiological study.

Of 366 consecutive patients with severe head injury, treated and managed by a uniform protocol, 61 (17%) were admitted with signs of severe brain-stem dysfunction. Forty-three of the 61 patients (70%) had surgical mass lesions and 30% had diffuse brain damage. Twelve of the 61 patients (20%) survived, but only six patients made a good to moderately disabled recovery. All six of these patients had a traumatic acute subdural hematoma (SDH). The records of the 20 comatose patients with an acute SDH and severe brain-stem dysfunction were reviewed to discover which factors contributed to functional recovery. The average survivor was operated on within 2 1/2 hours after injury and the nonsurvivors within 4 1/2 hours. Prompt surgical intervention and prudent control of postoperative intracranial pressure were major factors in preventing permanent brain-stem damage, with a significance of p less than 0.05 and p less than 0.02, respectively. Measurement of multimodality evoked potentials in the early postoperative period correctly distinguished between reversible and irreversible brain-stem dysfunction in six of the seven patients.

Adult↗
PubMed1984

Influence of stimulus location and limb position on motor responses in the comatose patient.

Motor responses to standardized stimuli were evaluated in 18 comatose patients with abnormal motor reactions. Painful stimuli were applied to three areas: the supraorbital, sternal, and medial aspects of the arm. Stimulations were carried out with the upper limbs first flexed and then extended. The initial position of the arm significantly influenced the posturing pattern. With the arm initially flexed there was a significantly higher percentage of abnormal flexor reactions, and the opposite occurred with the arm initially extended. Supraorbital stimulation yielded a significantly higher number of extensor responses. Arm stimulation, instead, caused a higher percentage of abnormal flexor reactions. When painful stimulation was applied to an arm initially flexed, the percentage of extensor responses was extremely low. Conversely, supraorbital stimulation with the arms extended yielded the highest percentage of extensor responses. The study shows that, within the frame of abnormal motor responses, the same patient can exhibit different reactions according to the site of stimulation and initial position of the upper extremities. These patterns are fairly constant and should be borne in mind in the evaluation of comatose patients.

Adult↗
PubMed1999

[Time constant of forward body sway induced by downward optokinetic stimulus].

Forward body sway induced by a downward optokinetic stimulus (OKS) was observed in 38 healthy subjects. The downward OKS was generated by a moving random dot pattern projected onto a half-pipe screen 2 m in diameter and was provided by a rectangular-like step function with velocities of 10, 20, 30 and 40 deg/sec. A fixation target was set by a red laser spot projected onto the screen in front of the subjects. As an additional stimulatory condition, 20 deg/sec of OKS with no fixation target was employed. The induced forward body sway was measured by a force-detecting platform as displacement of the center of gravity (COG). The gradual forward shift of COG followed by the plateau state was closely akin to a graphical representation of an equation of the first order lag time. As OKS velocities increased, the plateau level increased. Curve fitting analysis using a computer was employed to establish an approximation equation of the first order lag time. This analysis showed that the time constant of the optokinetic spinal response system was approximately 15 sec and the value of the time constant was independent of OKS velocity. Based on this long time constant, we concluded that the postural readjustment induced by OKS mainly plays a role in the low frequency range of human postural control.

Eye Movements↗
PubMed2002

[History of vestibular-spatial orientation research].

In order to advance our scientific endeavors in the field of vestibular-spatial orientation research, it is important to know how much research has already been carried out, and how much accurate information we currently possess. It is mandatory to have sufficient background information in order to establish a solid working hypothesis utilizing insightful approaches. Accordingly, this historical survey covers various research endeavors from the beginning of aviation until the end of 2001, including Skylab, Microgravity Vestibular Investigations, and Neurolab.

Humans↗
PubMed1992

[Postural control in the elderly].

In order to investigate postural control in the elderly, a stabilometric investigation including fast Fourier Transform (FFT) analysis was conducted in three different age groups. The oldest group was composed of 16 subjects who ranged in age from 75 to 86 years: another group consisted of eight 65 to 74 year olds; the control group was composed of 21 young students. The subject was instructed to stand and look for 30 seconds at a spot in a CRT 50 cm ahead of his eyes, and to control body sway as indicated by the gravitational spot in the CRT. The subject was then told to stand with eyes closed for 30 seconds. Next, a 100 Hz vibratory stimulation was applied to the bilateral Achilles tendon in each trial. The data was filtered with a 10 Hz high cut filter and digitized at 25 Hz, and subsequently analyzed by a microcomputer (PC9801 VM 2). Thus, statistical analysis was performed in terms of area, length, and total frequency spectra from 0.10 Hz to 10.0 Hz in both lateral and antero-posterior directions. Sixteen power spectra of 0.249 Hz step from 0.10 to 3.96 Hz were demonstrated in the CRT and were also compared with those of the young group. When standing naturally, significant increases in body sway were found in terms of area, length, and total frequency spectra in the most elderly group as compared with the other two groups. There was no significant change in Romberg ratio between the elderly and the young groups. However, FFT analysis confirmed the influence of visual cues. When vibration was applied, no increases in body sway with regard to these parameters were demonstrated in the elderly, whereas significant increases were found in the young control group. This was especially evident in the eyes-closed trials, as previously reported. There were few increased frequency ranges in either lateral or antero-posterior sway in the elderly. This might suggest that proprioceptive afferent information play a less important role in elderly than in young subjects. When the subject was requested to minimize his own sway by utilizing visual feedback, no difference was found in this parameter between the elderly and young groups. However, FFT analysis of the elderly group revealed an increase of the power spectra close to 1.0 Hz in both lateral and antero-posterior sway, whereas increases of approximately 1.0 and 2.0 Hz in the power spectra and a decrease in the power spectrum from 0.10 to 0.29 Hz were found in both directions in young subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗