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  • 1
    Electronic Resource
    Electronic Resource
    Vestibular nerve and nuclei unit responses and eye movement responses to repetitive galvanic stimulation of the labyrinth in the rat (1987)
    Springer
    Experimental brain research 66 (1987), S. 41-48 
    Details
    ISSN: 1432-1106
    Keywords: Vestibular habituation ; Vestibular nuclei ; Scarpa's ganglion ; Vestibuloocular reflex ; Galvanic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two-second cathodal current pulses were applied at one-minute intervals at a point external to the round window in the ear of each albino rat subject. Responses were recorded in the vestibular nerve ganglion, the vestibular nuclei (single units), or in the eye movements (search coil recording method) of anaesthetized, decerebrated, or alert rats. The unit responses to the galvanic stimuli were characterized and compared with responses to galvanic and rotational stimuli reported in the literature. The main focus of the study, however, was effects of stimulus repetition. In both the vestibular nerve and vestibular nuclei recordings, the responses of many units were substantially larger or smaller at the end of a 13-pulse stimulus train than at the beginning. In the vestibular nuclei, but not in the nerve, there was a slight bias towards a decrease in response magnitude, with 10/88 units showing decreases great enough to be considered as reflecting an habituation process. In contrast, the eye movement responses showed more consistent response decrements, especially in the alert condition, but also in the other conditions (none of the unit recordings were done in alert rats). It is concluded that some of the modifications underlying habituation of the vestibuloocular reflex probably occur in portions of the neuronal reflex pathways that are downstream from the vestibular nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236200
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  • 2
    Electronic Resource
    Electronic Resource
    On the role of vestibulo-ocular reflex plasticity in recovery after unilateral peripheral vestibular lesions (1985)
    Springer
    Experimental brain research 59 (1985), S. 267-272 
    Details
    ISSN: 1432-1106
    Keywords: Vestibuloocular reflex ; Labyrinthectomy ; Plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Although adaptive plasticity is a wellknown feature of the vestibulo-ocular reflex (VOR), deficits in VOR performance after unilateral labyrinthectomy are poorly compensated in a large percentage of cats. To assess whether VOR plastic capabilities are affected by labyrinthectomy, forced oscillation in front of a patterned surround was imposed in unilaterally labyrinthectomized cats. This experimental paradigm has been shown to be very effective in inducing adaptive VOR gain changes in intact animals. We demonstrate that plasticity of VOR gain is still present both in acute and chronic stages following vestibular lesions. By contrast, forced oscillation did not significantly alter the lesion-induced asymmetry of responses. We conclude that VOR gain control mechanisms are not used to their fullest possible extent in a large percentage of animals suffering unilateral vestibular damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230906
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Short- and long-term modifications of vestibulo-ocular response dynamics following unilateral vestibular nerve lesions in the cat (1983)
    Springer
    Experimental brain research 50 (1983), S. 259-274 
    Details
    ISSN: 1432-1106
    Keywords: Vestibuloocular reflex ; Functional recovery ; Vestibular nerve lesion ; Nystagmus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The dynamics of the horizontal vestibuloocular reflex (VOR) were determined in the dark prior to and at various time periods after unilateral removal of the vestibular nerve. One chronic group, consisting of cats that were operated at the age of 6 weeks or as adults, was studied 10.5 to 22 months later; an adult-operated group was measured 1–244 days postoperatively (p.o.). Between measurements cats were kept in a normal environment. In control animals the VOR gain was close to unity only up to certain stimulus velocities which varied amongst cats; thereafter a sharp drop in gain occurred probably due to saturation of central and peripheral neuronal responses. Therefore, VOR gains in lesioned animals were compared to the control responses yielding high gain. It is only at these small stimulus amplitudes that the two labyrinths maximally interact and, therefore, one would expect the largest changes. The gain was computed after correction for the ocular imbalance induced by the lesion. Immediately after the lesion a drop in gain to stimulations in both directions was noted; the reduction was larger for the VOR evoked on rotation to the lesioned side. Contrary to control animals, no partial response saturation occurred in lesioned animals but, following rotation to the lesioned side, complete saturation was noted with larger stimuli. Ocular balance was greatly improved within the first 3–4 days p.o. as indicated by the strong reduction of nystagmus. The time course of p.o. adaptive gain changes could be divided into three stages: in the initial stage (1–5 days p.o.) no improvement was visible; between p.o. days 5–10 one group of cats showed an abrupt increase in gain while it remained low in others. Response symmetry showed no consistent change in either group; the 3rd stage starting p.o. day 10 and extending throughout the observation period (22 months) is characterized by slowly developing changes reducing significantly response asymmetry. The incremental gain was higher in the young than in the adult-operated chronic cats. Compared to controls the phase plot of the VOR of lesioned animals shows a parallel shift of ca. 10 ° towards larger lead over the frequency range tested (0.05–1.0 Hz) independent of direction of rotation or p.o. stages. All lesioned animals showed a clear failure to hold eye position in the dark even in the chronic stage; a drift with an exponentially decreasing velocity of ca. 2–4 °/s was typical. The direction of the drift could be to the lesioned as well as to the intact side. The eyes seem to approach a new null point which is shifted towards the lesioned side. In conclusion on data show that while ocular balance recovers quite well and fast after unilateral lesions the VOR dynamics show some adaptive plasticity but also significant long-term deficits when measured in the dark and with the head fixed. Obviously, the striking recovery observed in the freely moving animal must be aided by other sensory systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239190
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    Paper (German National Licenses)
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