Semicircular Canal System Research Articles

Response characteristics of semicircular canal and otolith systems in cat. II. Responses of trochlear motoneurons

1. The electrical activity of single trochlear motoneurons (TMns) and axons of second order vestibular neurons presumably terminating on these motoneurons were studied during natural stimulation of semicircular canals and otolith organs in cats anesthetized with Ketamine. 2. Null point analysis showed that TMns received an excitatory canal input from the contralateral posterior canal, and labyrinthine lesion experiments suggested that the functionally synergistic, ipsilateral anterior canal provides an inhibitory input. A small number of motoneurons showed orthogonal canal convergence. 3. In addition to the canal projections most TMns received an otolithic input. Firing rate was proportional to lateral head tilt and was of the beta type. Most units also responded to pitch with an increase and decrease in firing rate on nose-up and nose-down positioning, respectively. Lesion experiments indicated that the otolith responses are the results of reciprocal innervation of TMns by contralateral (excitatory) and ipsilateral (inhibitory) otolith projections. 4. During sinusoidal rotation in yaw (canal only stimulation) the mean phase lag re acceleration of the response of TMns increased from 60 degrees at 0.025 Hz to 126 degrees at 1.0 Hz. In roll (canal plus otolith stimulation) the phase lag of TMn responses measured 180 degrees and 130 degrees at 0.025 and 1.0 Hz, respectively. Phase-lags measured in Vi and Vc axons were less by ca. 15 degrees. 5. The otolith contribution to TMn responses in roll was calculated by vectorial subtraction of the yaw from the roll responses: A phase lag of 10 (0.025 Hz) to 90 degrees (0.5 Hz) re. displacement was noted and gain was constant over the same range. Similar lag dynamics were revealed in TMns when studied during ramp displacement of the head. 6. The possible functional role of central canal-otolith convergence and the differences between the response of primary vestibular afferents and secondary vestibular neurons and TMns will be discussed.

Functional organization of vestibulofastigial projection in the horizontal semicircular canal system in the cat.

Spike potentials of fastigial nucleus neurons were recorded extracellularly in decerebrate, unanesthetized cats. The neurons responding to head rotation in the horizontal plane with a type I fashion were located mainly in the middle and caudal regions of the fastigial nucleus. Three fourth of these fastigial type I neurons were antidromically activated by stimulation of the contralateral vestibular nuclei. These neurons were excited transsynaptically from the ipsilateral vestibular nerve or nuclei. Intra cellular recordings were made from those neurons which were located in the caudal half of the fastigial nucleus and were activated antidromically from the contralateral vestibular nuclei. Stimulation of the ipsilateral vestibular nerve produced EPSPs in these neurons with latencies of 1.0-6.6 msec. The shortest conduction time along primary vestibular aggerents from the labyrinth to the ipsilateral fastigial nucleus was 0,7 msec. The EPSPs with the shortest latency of 1.0 msec were therefore postulated to be due to monosynaptic connections of primary vestibular afferents with fastigial neurons. Stimulation of ipsilateral vestibular nuclei also produced monosynaptic EPSPs in fastigial neurons. These EPSPs were facilitated by conditioning stimulation of the ipsilateral vestibular nerve, indicating the existence of polysynaptic activation of fastigial neurons from the ipsilateral vestibular nerve through the vestibular nuclei.

Symposium: new data for noise standards. V. Current status of labyrinthine cryosurgery.

Symposium: new data for noise standards. V. Current status of labyrinthine cryosurgery.

Pathological and functional alterations in the vestibular labyrinth following cryosurgery.

Definite pathologic changes were noted within the horizontal crista ampullaris after cryosurgery. The amount of damage was dependent upon the temperature of the crista during cooling. For example, when the horizontal crista was cooled to-70°C (intralabyrinthine temperature + 18°C) exudate was observed in the endolymphatic space. Electron microscopically, however, definite cellular damage (myelin figures) was detected primarily in the specialized cells (dark and light). Ruptures of the membranous wall of the crista was observed at cryosurgical dosage of-90°C (intralabyrinthine temperature + 13°C). Gross histological damage was noted when the horizontal crista was cooled to-120 and-190°C (intralabyrinthine temperature +5 and-6°C respectively). The functional (rotatory tests), ultrastructural and histologic results correlate extremely well. These results indicate that the critical cryosurgical threshold dosage necessary to alter the morphology and function of the semicircular canal system is approximately-70...

The effect of varying the time interval between equal and opposite coriolis accelerations.

The purpose of this experiment was to investigate the effect of varying the time interval between two equal and opposite Coriolis accelerations upon the duration of the subjective responses evoked by the second stimulus. It was also designed to evaluate certain predictions generated from a ‘torsion pendulum’ model of the neural events mediating these subjective phenomena.Theoretical curves derived from the torsion pendulum model approximated fairly closely the way in which the reported durations of the subjective phenomena increased as a function of the time interval between the two Coriolis accelerations. This result supported the a priori assumption that the neural events underlying the subjective phenomena are closely linked to mechanical events occurring within the cupula‐endolymph system. However, an explanation resting entirely upon peripheral phenomena would be inadequate to account for two additional findings: (1) the estimated time constants of signal decay were shorter than those expected on the basis of the known mechanics of the semicircular canal system, and (2) the persistence of the Coriolis sensation (feelings of apparent whole body motion without visual reference) was greater at all intervals than the Coriolis oculogyral illusion. Adequate explanation of these findings requires the postulation of additional central mechanisms.

Vestibular physiology and tests.

THE SUBJECT I have to cover today is immense. As I only have half an hour in which to tell you some of the facts, I have to simplify to give you an insight into this complicated problem, as complicated as the name labyrinth already suggests. In the inner ear we find two sense organs besides the organ of hearing: the semicircular canal system and the otolith organ. Both are sense organs because they react to specific stimuli with sensations and reflexes. In the case of the canal organ, rotatory-accelerated movements are the stimuli, and sensations of rotation and reflexes in the muscles of eyes, neck, limbs, and trunk are the responses. The stimulus for the otoliths is linear acceleration, the sensation is one of position (verticality), the reflexes again can be found in the muscles of the eyes, neck limbs, and trunk. As a result of a rotational acceleration,

Inhibition of central vestibular neurons from the contralateral labyrinth and its mediating pathway.

Inhibition of central vestibular neurons from the contralateral labyrinth and its mediating pathway.

CORRELATION OF SUSCEPTIBILITY TO SEASICKNESS TO VESTIBULAR FUNCTION

The people grouped together here as being susceptible to seasickness are otherwise normal individuals with normal vestibular function.The results of the present investigation can be summarized as follows :(1) Neither the resistant nor the susceptible groups show any spontaneous vestibular signs.(2) The longer duration of nystagmus and dizziness in both caloric and rotatory tests is generally associated with the higher susceptibility to seasickness, while resistant individuals are usually free of dizziness during the tests.(3) Susceptible group shows the characteristic pattern in our rotatory pattern test and caloric pattern test.(4) Functional unbalance of bilateral labyrinths has no significant relation to the susceptibiltity to seasickness. The test of semicircular canal system is also important to the study of seasickness.

The Semicircular Canal System of the Organs of Equilibrium - II

The function of the semicircular canal system is considered on the mechanical basis of the heavily damped torsion pendulum. It appears that this point of view has a first approximation validity. The deviations in the responses from the predicted mechanical behaviour point mainly to an inhibition of central origin. The so-called ` normal test subject ' tends to suppress the signals passing the stations between labyrinth and brain in a progressive manner: nystagmus is less distorted than sensation. A comparison between these two responses may yield information on the (dis)function of the vestibular tract.

The Semicircular Canal System of the Organs of Equilibrium - I

The function of the semicircular canal system is considered on the mechanical basis of the heavily damped torsion pendulum. It appears that this point of view has a first approximation validity. The deviations in the responses from the predicted mechanical behaviour point mainly to an inhibition of central origin. The so-called ` normal test subject ' tends to suppress the signals passing the stations between labyrinth and brain in a progressive manner: nystagmus is less distorted than sensation. A comparison between these two responses may yield information on the (dis)function of the vestibular tract.

“Considerations Regarding the Secondary After Sensations Caused by a Stimulation of the Semicircular Canal System”

An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.

Considerations Regarding the Secondary After-Sensations Caused by a Stimulation of the Semicircular Canal System

Considerations Regarding the Secondary After-Sensations Caused by a Stimulation of the Semicircular Canal System

THE PRESENT STATUS OF VERTIGO CONSIDERED FROM A DIAGNOSTIC STANDPOINT

In the discussion of suppurative labyrinthitis before this section at the Chicago meeting in June, 1908, it was my privilege and good fortune to present the first paper to appear in the medical literature of this country, reporting the recent progress made in the diagnosis and treatment of labyrinthine diseases, as taught in the Vienna schools. Since then the literature on this subject has been added to very materially, notably by Mac-Kenzie 1 of Philadelphia, Fridenberg, 2 and Richards 3 of New York, and Mr. Scott 4 of London, the last contributing some valuable new research data relating to the functions of the semicircular canals. 5 My first contribution was rather a foreword, very briefly outlining the methods of functional tests of the semicircular canal system developed by the researches of Barany, Alexander and Neumann of Vienna. The basis of these tests was founded on the fact that stimulation of