Takashi Tokita

Modulation by Head and Trunk Positions of the Vestibulo-spinal Reflexes Evoked by Galvanic Stimulation of the Labyrinth Observations by Labyrinthine Evoked EMG

Modulation by head and trunk positions of the vestibulo-spinal reflexes was studied in the soleus muscle activities induced by galvanic stimulation of the labyrinth. The stimulation was applied using a bipolar-biaural method with the cathode on the right ear and the anode on the left ear. The intensity was 1 mA and duration 3 s. 1) When the labyrinth was stimulated with the head facing forward, soleus muscle activities increased on the right side and decreased on the left, with a latency of about 100 ms. In spite of the same stimulation, activities of the soleus muscle on both sides decreased with the head rotated to the right and increased with the head rotated to the left. 2) The responses in upper-body rotation were the same as in the case of head rotation. 3) In trunk rotation, some cases showed the same responses as with the trunk facing forward in rotation to the right and left, while others showed changes in muscular activities with the head rotation caused by rotating the trunk. 4) Changes in labyrinthine evoked EMG by head and trunk positions were considered to be due to interaction of vestibular and proprioceptive inputs on the interneurons of the spinal cord.

DYNAMIC CHARACTERISTICS OF THE OTOLITHIC OCULOMOTOR SYSTEM

Vertical eye tracking test, up-down test, and running test in the dark and light were carried out to obtain Bode plots of transfer function of the opto-oculomotor, otolithic oculomotor, and opto-otolithic oculomotor systems. 1. The gain and phase of the opto-oculomotor system obtained from the vertical eye tracking test were flat in a frequency range of 0.3 to 1.0 Hz. 2. During the up-down test in the dark, the gain of the otolithic oculomotor system linearly increased at the rate of 20 dB/decade with an increase of frequency from 0.7 to 5 Hz. 3. During the up-down test in the light, the gain and phase were flat in a frequency range of 0.3 to 2.5 Hz. 4. The transfer function calculated with vertical head acceleration as input and vertical eye movement as output in the running test in the dark was similar to that in the light. The gain linearly decreased at the rate of 40 dB/decade with increase of frequency from 0.3 to 3.0 Hz. During running, eye displacement is almost in proportion to the head displacement in both dark and light. In daily, active movement such as running, eye movement proportional to head displacement appears without collaborative action of the opto-oculomotor system. 5. All five patients with bilateral loss of labyrinthine excitability exhibited a similar opto-oculomotor response to that of normal subjects. Three of the five patients did not show any eye movement corresponding to head movement in the up-down test in the dark. However, two patients showed a periodic eye movement in the same test, indicating dispersion of the gain and phase values. 6. These patients exhibited a rhythmic eye movement corresponding to head movement in the running test in the dark and light. However, values of gain and phase obtained in both tests were cultured. The variations in gain obtained from the running test in the light were observed in frequency ranges above and below 1 Hz.

Über Die Beziehung Der Richtung Der Optischen Reize Zu Den Reflextypen Der Augen- Und Skelettmuskeln: Einleitung

Uber den Einfluss der Drehreize auf die Art und Weise der Labyrinthreflexe liegt schon heute eine Reihe von Untersuchungen wie von Crum Brown, Ewald u. a. vor. Nach diesen Autoren reagiert namlich das Labyrinth auf die gegebenen Reize beiderseits nicht im gleichen Sinne, sondern nur auf der einen Seite im gleichen Sinne wie die Richtung des Drehreizes, also hauptsachlich auf der rechten Seite, wenn der Drehreiz nach rechts, und auf der linken, wenn er nach links gerichtet ist (Abbildung i).ZusammenfassungZur Untersuchung einer etwaigen Beziehung zwischen den Reflextypen der Ske-lettmuskeln, besonders der Augenmuskeln einerseits und der Richtung des optischen Reizes anderseits, haben wir Versuche mittels eines grossen Drehzylinders bei Kaninchen und Meerschweinchen, Hund und Katze sowie beim Menschen durch-gefuhrt und vor allem folgendes ermittelt:1. Beim Binocularsehen tritt ein Augennystagmus bei optischer Reizung immer auf, gleichgultig in welcher Richtung diese geschieht, und in dieser Hinsicht lasst s...

Provocation of labyrinthine reflex by visual stimuli; evaluation of the theory of subliminal rotation.

Recently, a new method of examination on the labyrinthine function called the subliminal rotation (Egmond, Arslan) has been universally put into practice in the place of Baranys method. This method is based upon the theory which establishes a threshold of angular acceleration about the labyrinthine function when a man or an animal is rotated. The cupulometry is also founded on this theory. It insists that the labyrinth remains unstimulated if the subject is rotated at such a low angular acceleration below a certain limit as to cause no perrotatoric nystagmus. The purpose of this paper is to criticize this theory, producing counter-evidence especially in regard to the optic condition of the subliminal rotation.The labyrinth never remains unstimulated at the so-called subliminal rotation; the perrotatoric nystagmus is not induced only because the subject is under a special visual condition. The fact is that the labyrinth is stimulated and reacts in promoting the optokinetic nystagmus.The labyrinth favours ...

A characteristic pattern in the postural sway of unilateral vestibular impaired patients.

The statistical properties of the center of pressure (COP) change over time, and -invariant methods of the COP analysis is not sufficient to monitor the changes. Therefore, dynamic temporal information of the COP signals has been important in assessing the postural stability. The purpose of this study was to evaluate the characteristic pattern of time-frequency dynamics during the upright stance in patients with unilateral vestibular dysfunction (UVD). This study included 20 dizzy patients with UVD and age-matched 20 control subjects without any vestibular disorder. The COP signals were collected using a single standard force platform and a spectral analysis including the time-frequency dynamics was carried out on the basis of the maximum entropy method (MEM) by using a segment time series analysis. The power spectral density (PSD) analysis exhibited an exponential decreasing shape (1/f (-)(β)) when plotted on a double logarithmic scale. The average value of β in the low frequency range of less than 1 Hz in the UVD group was significantly lower than that in the control group (p < 0.05) in the medial-lateral (ML) direction under eyes closed condition. In the segment time series analysis, the peak frequency of the COP signals in the patients with UVD gradually converged to the frequency range of 0.1-0.2 Hz in the ML direction under EC condition. Our results suggest that the segment time series analysis of the COP signals can derive a characteristic pattern related to the UVD. It may indicate an increased reflexivity of the COP fluctuation by the UVD, resulting in inducing the instability.

Static and Kinetic Labyrinthine Reflex: Functional Development of Labyrinthine Function with Rotatory Training

Two blindfolded leghorns were rotated 100 times in 200 seconds to both directions every day for two weeks. Their labyrinthine function was evaluted by Baranys rotation test before and after the repeated rotations.It was observed that after the rotations the head during rotation turned in the direction of rotation after the normal deviation. This phenomenon was never found in animals before repeated rotations. The labyrinthine function which caused it has been named the “kinetic labyrinthine reflex”. In contrast with this naming, the normal deviation during rotation, a hitherto well known labyrinthine reflex, has been called the “static labyrinthine reflex”.After repeated rotations the animal was much less ataxic during and after the test rotation: the animal showed a functional progress in equilibrating function through the repeated rotations, which were therefore named “training”Postrotatory head-nystagmus was also much less marked in the trained animals.

Chapter 25 Labyrinthine control of upright standing posture in humans

To clarify the role of the labyrinth in the regulation of upright standing posture, vestibular control of the soleus muscle was studied by reference to the evoked EMG induced by galvanic stimulation of the labyrinth in humans. Galvanic labyrinthine stimulation induced ipsilateral excitation and contralateral inhibition of soleus muscle activity with a latency of about 100 ms. The inhibition was stronger than the excitation and showed predominance of the long-latency component in the evoked responses. These results indicated that the labyrinthine system exerts a prominent inhibitory influence on spinal extensor mechanisms. The predominance of this inhibitory control explained the peculiar forward-backward sway observed in the upright standing posture of patients with bilateral loss of labyrinthine function. In general, the role of the labyrinth in postural regulation has been explained on the basis of the facilitatory effect exerted by the lateral vestibulospinal tract on the extensor muscles. However, for the total labyrinthine system, the inhibitory influence upon the extensor is more important for postural regulation.

A Quantitative test of Optokinetic Nystagmus and its data Processing by computer

A quantitative test of optokinetic nystagmus was proposed. Horizontal nystagmus was examined by a large rotating cylinder with vertical stripes. Nystagmus responding to the cylinder rotation with an acceleration of 2°/sec2 for 90 seconds was recorded with an electro-nystagmograph. On the records, the number of beats, average eye-speed, and average amplitude per each 10 seconds were calculated. This method was suitable for testing the nature of optokinetic nystagmus which indicates the ability of the eyes to adapt to objects moving through the visual field. Moreover, in order to save trouble in hand-scoring of each parameter of nystagmus, computer processing of electronystagmographic data was introduced. The results were printed numerically on the teletypewriter, and displayed graphically on a cathode ray tube and X-Y recorder. By displaying measured values on the form already printed with the normal ranges, the evaluation of the results was performed readily and objectively.

Studies on vestibulo-spinal reflexes by examination of labyrinthine-evoked EMGs of lower limbs.

Evoked electromyograms (EMGs) induced by galvanic stimulation of the labyrinth were examined in the muscles of the lower limbs. The labyrinthine-evoked EMGs appeared in the muscles of the femoral and gluteal regions and of the legs, and these muscle activities were changed by the head position in spite of the labyrinthine stimulation being the same. The vestibulo-spinal reflexes fulfil these functions in coordination with the neck proprioceptor.

Analysis of the Vestibulo-spinal system with a Five-dimensional feedback model

The role of the vestibulo-spinal system involved in the maintenance of upright standing posture was studied by a time series analysis with a 5-dimensional feedback model. The system was composed of sways of the head, shoulders, hips and activities of the nuchal and soleus muscles. The results were displayed as determinants of noise correlation matrix, power spectrum, correlogram, transfer function and relative power contribution. The five movements constitute a feedback system in normal subjects. Bilateral loss of labyrinthine function indicates a break in the feedback system. The power spectrum and relative noise contribution indicate that the vestibulo-spinal system regulates low-frequency body sway in upright standing. However, the contribution of the system was low in the overall control of standing posture.