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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 26 (1976), S. 89-103 
    ISSN: 1432-1106
    Keywords: Vestibular ; Oculomotor ; Canal ; Inhibition ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anesthetized albino rabbits, electric pulse stimulation was applied to ampullary branches of the vestibular nerve. Reflex discharges evoked from a canal in an extraocular muscle were depressed very effectively by conditioning stimulation at a certain other canal. The present systematic survey revealed that this reflex depression occurred specifically in 3 combinations of conditioning and testing canals; 1. anterior and posterior canals of the same side; 2. anterior and posterior canals of the opposite sides; and 3. horizontal canals of the two sides. Occurrence of postsynaptic inhibition in oculomotor neurons, on the other hand, was indicated by appearance of slow muscle potentials in extraocular muscles. It was confirmed that this motoneuronal inhibition did not contribute to the reflex depression in the above combination (1). Even in combinations (2) and (3), the accompanying motoneuronal inhibition was eliminated by adjusting intensities of canal stimuli or by severing its pathway in the medulla, or it was discriminated from the reflex depression by their different latencies and time courses. Hence, it was concluded that the reflex depression was attributable, at least largely, to non-motoneuronal inhibition, presumably postsynaptic inhibition at relay neurons for vestibulo-ocular reflexes. Slow muscle potentials evoked from a canal were also used as testing responses, but their depression could not be detected after conditioning at other canals.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 8 (1969), S. 190-200 
    ISSN: 1432-1106
    Keywords: Vestibular ; EPSP ; IPSP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurones in the descending, medial and superior vestibular nuclei of the cats were explored with intracellular microelectrodes. Cerebellar- and spinal-projecting neurones were identified by their antidromic invasion from the region of fastigial nuclei and from the second cervical segment, respectively, and the others by their location. The central actions of the primary vestibular impulses upon these non-Deiters vestibular nuclei neurones were investigated by using electric stimulation of the ipsilateral vestibular nerve. Many of these cells received excitatory postsynaptic potentials (EPSPs) monosynaptically, similar to those evoked in the ventral Deiters neurones, as described elsewhere, except that the unitary EPSPs are often larger. Some cells received only polysynaptic EPSPs or IPSPs and a few cells were not influenced at all.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Adaptation ; Vestibular ; Ocular ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Adaptability of the horizontal vestibulo-ocular reflex (HVOR) and the optokinetic response (OKR) was examined in alert albino rabbits during sustained runs lasting 5–12 h under four different stimulus conditions. (1) Sinusoidal rotation of the rabbit in darkness by 5 ° at 1/10 Hz, or (2) sinusoidal movement of a vertical slit light by 2.5 ° or 5 ° at 1/10 Hz around the optical axis of the stationary rabbit, affected the gain of neither the HVOR nor the OKR. (3) Combination of the stimulus as in (1) with the stationary slit light increased the gain of the HVOR gradually. A plateau at about 140% of the initial control was reached in 5 h. (4) Combination of the stimulus as in (1) with the slit light movement by 10 ° in phase with the turntable decreased the HVOR gain gradually, a plateau being obtained at about 70 % of the initial control in 5 h. Changes of the HVOR gain induced in conditions (3) and (4) were not frequency-specific and accompanied by no significant modification of either the gain or phase of the OKR or the linear property of HVOR-OKR interaction. A small but significant change of the HVOR phase was also detected under the condition (3) but not (4).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 18 (1973), S. 446-463 
    ISSN: 1432-1106
    Keywords: Cerebellum ; Vestibular ; Spinocerebellar ; Purkinje ; Deiters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The organization of the cerebellar, vestibular and spinal inputs to the lateral and medial vestibulospinal tract (LVST and MVST) cells was studied in anaesthetized rabbits. Synaptic actions of these inputs were determined by recording postsynaptic potentials intracellularly and also unit spike discharges extracellularly from a number of LVST and MVST cells. As reported previously in cats, inhibition was evoked very frequently from the vermal cortex of the cerebellar anterior lobe and less frequently from that of the posterior lobe. However, no such inhibition was derived from the flocculus. The cerebellar inhibition was exerted upon both LVST and MVST cells, whether they received monosynaptic activation from the primary vestibular afferents (second-order) or not and whether they conducted impulses fast or slowly. However, the inhibition was frequently absent in “slow” “second-order” MVST cells. The vast majority of LVST and MVST cells received an excitatory input from the spinocerebellar afferents ascending the funiculus posterolateralis. This input was particularly prominent from the upper cervical cord. The spinal excitation thus obtained occurred in close connection with the cerebellar inhibition. Hence, it appears that the cerebellar vermis receives the spinal signals that drive LVST and MVST cells and in turn sends out inhibitory signals to adjust the reflex activity in these cells.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Vestibular ; Ocular ; Optokinetic ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dynamic characteristics of the horizontal vestibulo-ocular reflex (HVOR), the optokinetic response (OKR), and their interactions were investigated in alert albino rabbits. For stimulation of the horizontal semicircular canals, the whole rabbit was rotated sinusoidally on a motor-driven turntable at peak-to-peak amplitudes of 5 ° to 30 ° over a frequency range of 1/30 to 1/2 Hz. Optokinetic stimulation was provided by a narrow vertical slit light source presented in front of the eye to be tested. The evoked horizontal eye movements were observed and measured by means of a closed circuit television system adapted to provide an analog signal proportional to the eye movement. The net HVOR was obtained by rotation of the turntable in darkness and the net OKR by rotation of the light source. Combining rotation of the turntable with a stationary light source immediately increased the gain and reduced the phase shift of the HVOR. The light source moving in phase with the turntable, but at twice the angular amplitude, reduced the gain and advanced the phase of the HVOR. Eye movement curves of the HVOR modified by a fixed or moving slit light could be reconstructed approximately by a linear combination of the net HVOR and OKR.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 14 (1972), S. 511-526 
    ISSN: 1432-1106
    Keywords: Vestibular ; IIIrd nucleus ; Flocculus ; Inhibition ; Picrotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized rabbits, the vestibulo-ocular reflex was evoked by electric stimulation of VIIIth nerve and was observed by recording postsynaptic potentials and relevant field potentials in Illrd nucleus. The electric stimulation of flocculus produced a prominent inhibition of the vestibulo-ocular reflex in both the inhibitory component relayed by the superior vestibular nucleus and the excitatory component mediated by the brachium conjunctivum. The excitatory component mediated by the medial vestibular nucleus appeared to be free of the flocculus inhibition. The flocculus inhibition was blocked very effectively by systemic injection of picrotoxin. That the flocculus inhibitory action is due to monosynaptic postsynaptic inhibition of secondary vestibular neurones was demonstrated by direct stimulation of, and also by recording from, the superior nucleus. Recording from the superior nucleus was also performed in anaesthetized cats. All of these above results indicate that Purkinje cells in flocculus projecting to vestibular and cerebellar nuclei cells have inhibitory synaptic action. Flocculus stimulation produced also an excitatory effect upon vestibular nuclei neurones. However, this effect could be attributed to intracerebellar activation of the primary vestibular fibers which pass into the flocculus.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 13 (1971), S. 306-326 
    ISSN: 1432-1106
    Keywords: Vestibular ; IIIrd nucleus ; PSPs ; Picrotoxin ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Microelectrodes were inserted into IIIrd cranial nucleus of anaesthetized rabbit. IIIrd nucleus was identified by observing the field potentials evoked antidromically by stimulation of IIIrd cranial nerve. After stimulation of VIIIth nerve extracellular field potentials, spike potentials in secondary vestibular fibers, and postsynaptic potentials in IIIrd nucleus neurones were recorded. VIIIth nerve impulses either excite or inhibit IIIrd nucleus neurones postsynaptically with disynaptic latencies around 1.7 msec. By local stimulation of the medulla, it was found that the secondary vestibular impulses inhibiting IIIrd nucleus neurones are mediated by the superior nucleus. The excitatory impulses are relayed by the rostral half of the medial nucleus as well as a certain structure(s) relevant to the brachium conjunctivum. Preliminary pharmacological investigations on the inhibition of IIIrd nucleus neurones are reported.
    Type of Medium: Electronic Resource
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