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1.
Neuroscience ; 8(4): 809-17, 1983 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-6866265

RESUMO

Unilateral lesions of the cerebellar flocculus were performed in three chronically-implanted adult cats. Following the lesion a spontaneous nystagmus was observed in the dark, with the fast phase directed to the lesioned side. Vestibulo-ocular responses in the dark became asymmetrical. Responses to velocity steps exciting the labyrinth ipsilateral to the lesion were strongly increased. A decrease, although less marked, was observed in the opposite direction. Responses to sinusoidal oscillations in the dark were also asymmetric with respect to both the cumulative eye displacement during rotation in the two directions and the interval between two consecutive reversals of eye movement. These differences were greater at the lower tested frequencies (0.01 HZ) than at the higher (0.1 HZ). Spontaneous nystagmus disappeared in about 10 days and a complete symmetry of the vestibulo-ocular responses was restored in about 3 weeks. It is concluded that a unilateral lesion of the flocculus leads to two separate, but interacting, effects upon vestibulo-ocular responses.


Assuntos
Cerebelo/fisiologia , Fenômenos Fisiológicos Oculares , Núcleos Vestibulares/fisiologia , Animais , Gatos , Cerebelo/patologia , Movimentos Oculares , Músculos Oculomotores/fisiologia
2.
Brain Res ; 302(2): 245-56, 1984 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-6610459

RESUMO

The behavioral effects of vestibular endorgan lesions were compared with those of vestibular ganglion lesions in the albino rat. No differences in head tilt angle or spontaneous eye nystagmus beat frequency were noted between the two groups during the first 36 h after the lesion was made. Of rats studied beyond 36 h, 2/7 with lesions restricted to the endorgans and 2/3 with ganglion lesions showed pronounced secondary increases in head tilt and tonic eye deviation, but not eye nystagmus. Single units were recorded in the ganglion acutely, as well as 1,2, and 14 days after an endorgan lesion was made. Practically no resting activity could be recorded in the ganglion acutely (2-7 h) after endorgan damage, and the resting activity at subsequent times was slight. It is concluded that an intact vestibular ganglion isolated from the sensory periphery is of no functional significance during the first 36 h, when the largest decreases in magnitude of the behavioral signs of unilateral labyrinthectomy occur in the rat. A slight significance at later times is not ruled out.


Assuntos
Dominância Cerebral/fisiologia , Regeneração Nervosa , Equilíbrio Postural , Nervo Vestibular/fisiologia , Vestíbulo do Labirinto/inervação , Vias Aferentes/fisiologia , Animais , Orelha Interna/inervação , Feminino , Masculino , Degeneração Neural , Nistagmo Fisiológico , Orientação/fisiologia , Ratos , Ratos Endogâmicos
3.
Brain Res ; 239(1): 251-7, 1982 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-7093679

RESUMO

Unilateral lesions of the cerebellar flocculus were made in two groups of cats chronically implanted for eye-movement recording. In the first group (3 cats), the floccular lesion preceded by 40-70 days a unilateral labyrinthectomy on the contralateral side. In the second group (5 cats), the serial order of the two lesions was reverted, the unilateral flocculectomy following unilateral labyrinthectomy by about 60 days in 2 animals and by 16-27 months in the other 3. The effects of the unilateral labyrinthectomy on the vestibulo-ocular reflex (spontaneous nystagmus and asymmetrical responses) were extensively tested by using natural vestibular stimulations. It was found that recovery from these effects was severely delayed in animals from the first group (flocculectomy prior to labyrinthectomy), although in animals from the second group the flocculectomy secondary to the labyrinthectomy only produced a transient asymmetry of vestibulo-ocular responses. It is concluded that the flocculus is required for initiating (not for maintaining), the compensatory process following peripheral lesions of the vestibular system.


Assuntos
Cerebelo/fisiologia , Orelha Interna/fisiologia , Animais , Gatos , Movimentos Oculares , Lateralidade Funcional , Cabeça , Cinética , Movimento
4.
Neurosci Lett ; 12(2-3): 295-9, 1979 May.
Artigo em Inglês | MEDLINE | ID: mdl-460725

RESUMO

Vestibulo-ocular response (VOR) has been recorded in kittens aged between 10 and 61 postnatal days. Responses to velocity steps and to sinusoidal oscillations are present on the earliest recordings, though they are limited to a low gain slow compensatory gaze displacement. Vestibular-induced saccades appear only around postnatal day 30, but adult-like responses with a high gain are not displayed before the end of the second month. Optokinetic nystagmus (OKN) appears earlier (around postnatal day 25) and maturates faster.


Assuntos
Testes de Função Vestibular , Visão Ocular , Envelhecimento , Animais , Bovinos , Olho/crescimento & desenvolvimento , Olho/inervação , Fenômenos Fisiológicos Oculares
5.
J Vestib Res ; 6(2): 61-70, 1996.
Artigo em Inglês | MEDLINE | ID: mdl-8925117

RESUMO

Acetylcholinesterase (AchE) activity was studied in pigmented rats 6 h to 1 y after hemilabyrinthectomy. A strong reduction of this activity was localized in the rostrocaudal extent of both the prepositus hypoglossi nucleus and the medial vestibular nucleus (that is, medial vestibular complex: VCm) ipsilateral to the lesion 6 h after the lesion. This deficit persisted within some areas dispersed throughout this complex 3 w and 1 y postoperatively. This result supports the hypothesis that the asymmetry of AchE activity in VCm could be necessary for vestibular compensation and provides an additional model for functional plasticity in the central nervous system.


Assuntos
Acetilcolinesterase/metabolismo , Orelha Interna/fisiologia , Eminência Mediana/enzimologia , Substância Cinzenta Periaquedutal/enzimologia , Núcleos Vestibulares/enzimologia , Animais , Orelha Interna/cirurgia , Histocitoquímica , Ratos
6.
Arch Ital Biol ; 133(4): 251-61, 1995 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-8849316

RESUMO

In the rat, after unilateral labyrinthectomy the loss of unit responses in the deafferented ipsilateral vestibular nucleus should lead to a complete postlesional asymmetry in H-OKN. The compensation process of this oculomotor deficit were recorded by means of a search coli technique using amplitude detection in 30 pigmented rats, 8 animals as control and 22 submitted to left hemilabyrinthectomy. Recording sessions were performed from day 1 to 8 after the lesion. Velocity steps of visual stimulation were delivered in clockwise (CW) and counterclockwise (CCW) directions at velocities from 2 to 40 degrees/s. The H-OKN was not observable on postlesional day 2. It reappeared asymmetrical on day 2 with depressed responses to CW stimulation while the response to the CCW stimulation were almost as large as in intact animal. This asymmetry was quantified by the gain values (eye velocity/stimulus velocity) of the nystagmic responses which were, at 5 degrees/s of stimulus velocity, 0.37 for CW stimulation and almost twice as large, 0.72 for CCW stimulation. Later this asymmetry was consistently reduced by a progressive increase of the CW responses and a parallel decrease of the CCW. This process led to the responses to reach almost symmetrical values on day 8 with a gain of 0.52 and 0.63 for CW and CCW responses respectively at the same stimulus velocity. However the gain of intact animals was never attained. The initial eye velocity was symmetrically altered on day 2 and remained unchanged until postlesional day 8. These results demonstrate that the deficit appeared to be compensated more by a restoration of a symmetry than by a restitution of a gain of responses equivalent to that of an intact animal.


Assuntos
Orelha Interna/fisiologia , Nistagmo Optocinético/fisiologia , Vias Aferentes/fisiopatologia , Animais , Denervação , Orelha Interna/cirurgia , Masculino , Ratos , Fatores de Tempo
9.
Exp Brain Res ; 59(1): 10-5, 1985.
Artigo em Inglês | MEDLINE | ID: mdl-3874786

RESUMO

In order to clarify the problem of which stimulus parameters affect vestibular habituation, a group of cats was submitted to repeated velocity steps involving changes in either the step amplitude or the interval between two consecutive steps. In the first two experiments, the protocol was the same as in a previous study which used steps of 160 degrees/s separated by 60 s, except that the steps were of 80 degrees/s and 16 degrees/s. In the remaining experiments the step amplitude was kept constant (160 degrees/s) and the interstimulus interval was changed: each step was delivered either immediately after the reversal of the nystagmus elicited by the preceding step (only a few beats in the reversed direction were allowed to occur) or immediately before (no beats in the reversed direction). Vestibular habituation was found to occur in both experiments of the first series. Nevertheless, the marked initial suppression of the response, that was reported as one aspect of vestibular habituation to steps of 160 degrees/s, was clearly present when steps of 80 degrees/s were used, but was not as clear when the step amplitude was reduced to 16 degrees/s. The experiments of the second series showed that a typical vestibular habituation still occurs when steps are delivered just after the reversal of nystagmus. On the contrary, no habituation was observed when steps preceded the reversal of nystagmus. It was concluded that the presence of an anticompensatory phase is interpreted by the central nervous system as a sign that the response evoked in a reflex way is functionally meaningless or even detrimental. An habituation process is then started to suppress the response.


Assuntos
Habituação Psicofisiológica/fisiologia , Nistagmo Fisiológico , Vestíbulo do Labirinto/fisiologia , Animais , Fenômenos Biofísicos , Biofísica , Gatos , Movimento (Física)
10.
Exp Brain Res ; 28(3-4): 249-57, 1977 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-885180

RESUMO

A photographic technique was used to study the evolution of lateral head-tilt following hemilabyrinthectomy in adult cats. Animals were maintained post-operatively in normally lit conditions (LM cats), in total darkness (DM cats), or in stroboscopic light. In LM casts, the head tilt peaked at 45 degrees (with the lesionned side down) on the second post-operative day, and decreased to about 0 degree within about 10 days. This evolution was followed by rebounds of head-tilt to large angles before a stable compensated head postion could be maintained (approximately at the end of the third post-operative month). In DM cats the head remained tilted by a large angle throughout the duration of the dark period. Re-exposure to light was followed by a rapid decrease of head-tilt. In stroboscopic light, the evolution of head-tilt was found to be closely similar to that in the normally lit condition. Finally, when put back in the dark at a late post-operative stage, already compensated animals were found to loose their symmetrical head position, and to re-acquire a strong head tilt. This effect resumed on re-exposure to light. It is inferred that static visual input is a necessary condition for compensation of the postural deficits of hemi-labyrinthctomy in the cat. Maintenance of a stable head posture also depends upon continuous availability of visual input.


Assuntos
Orelha Interna/fisiologia , Postura , Animais , Gatos , Escuridão , Cabeça , Luz
11.
Exp Brain Res ; 132(4): 457-63, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10912826

RESUMO

It is known that the medio-posterior cerebellar lobules VI/VII of the vermis and caudal part of the fastigial nucleus (cFN) are involved in the control of saccadic displacements of the visual axis in space (gaze). We have recently shown in the head-unrestrained cat that inactivation of the cFN severely impairs the accuracy of orienting gaze shifts toward visual targets by altering the amplitude of both eye and head components. In the present paper, we report additional data that indicate that the deficits induced by cFN inactivation are not restricted to saccadic gaze shifts but extend to the forward reaching movement of the whole body toward a visual target. Indeed, the path followed by the animal walking toward a visible food target was systematically curved toward the inactivated side. This deficit could largely be accounted for by an angular bias in the heading direction used by the animal to reach the target. These data suggest that pharmacological inactivation of the cFN leads to a general deficit in spatial orientation.


Assuntos
Núcleos Cerebelares/fisiologia , Locomoção/fisiologia , Desempenho Psicomotor/fisiologia , Gravação em Vídeo , Animais , Gatos , Núcleos Cerebelares/lesões , Agonistas GABAérgicos , Muscimol
12.
Exp Brain Res ; 48(2): 279-87, 1982.
Artigo em Inglês | MEDLINE | ID: mdl-7173363

RESUMO

Cats reared in stroboscopic illumination (strobe reared cats) have been found to have abnormal eye movements. Visual and vestibular evoked compensatory eye movements were inefficient. Vestibulo-ocular reflex in the dark had a maximum gain of 0.6 (1.0 in normal animals). Optokinetic nystagmus had a mean gain which approached unity only at stimulus velocities around 7 degrees/S (up to 30 degrees/S in normal animals). The asymmetry of the optokinetic nystagmus resulting from monocular stimulation was more pronounced in strobe reared cat than in normal animals. Interaction between vestibulo-ocular reflex and optokinetic nystagmus to give adequate compensatory eye movements was absent in strobe reared cats: visual suppression of vestibulo-ocular reflex was absent when the animal was rotated in an illuminated environment which remained stationary with respect to the head. Optokinetic nystagmus failed to improve the gain of the vestibulo-ocular reflex when the animal was rotated in a normally lit environment. The deprived animals showed no signs of recovery after 5 months exposure to normal lighting.


Assuntos
Nistagmo Fisiológico , Reflexo/fisiologia , Privação Sensorial/fisiologia , Núcleos Vestibulares/fisiologia , Percepção Visual/fisiologia , Animais , Gatos , Comportamento Exploratório/fisiologia , Movimentos Oculares , Percepção de Movimento/fisiologia , Nervo Oculomotor/fisiologia , Estimulação Luminosa , Colículos Superiores/fisiologia , Córtex Visual/fisiologia
13.
Exp Brain Res ; 42(1): 34-42, 1981.
Artigo em Inglês | MEDLINE | ID: mdl-6971232

RESUMO

1. Unilateral habituation of the vestibulo-ocular reflex was produced in adult cats stimulated by repeated unidirectional velocity steps (vestibular training) or by a continuously moving visual surround (optokinetic training). -- 2. Unidirectional vestibular training produced a strong asymmetry of vestibulo-ocular responses (VOR). Responses to velocity steps applied to the "trained" labyrinth were decreased both in gain and in time-constant. This effect generalized to responses to sinusoidal oscillations (0.03 Hz to 0.1 Hz), i.e. to a stimulus not used during training. -- No spontaneous nystagmus was ever observed in spite of the dynamic VOR asymmetry. -- 3. Unilateral vestibular habituation produced by vestibular training appeared to be a long-lasting phenomenon. It was still present 10 days after the end of training. -- 4. Optokinetic responses were not affected by vestibular training. -- 5. Unidirectional optokinetic training produced an increase in the slow phase velocity of optokinetic nystagmus (OKN) by about 25% in both directions. This effect did not persist for more than a few minutes. A marked spontaneous nystagmus was recorded in the dark after each session of optokinetic training, with a slow phase in the direction opposite to the previous OKN. -- 6. VOR in response to velocity steps and to sinusoidal oscillations were decreased unilaterally after optokinetic training. This effect was of short duration, however, and disappeared within the interval between training sessions. This lack of retention contrasted with the prolonged effect of vestibular training.


Assuntos
Estimulação Acústica , Movimentos Oculares , Habituação Psicofisiológica , Estimulação Luminosa , Nervo Vestibular/fisiologia , Vestíbulo do Labirinto/fisiologia , Visão Ocular , Animais , Gatos , Reflexo
14.
Perception ; 10(5): 519-24, 1981.
Artigo em Inglês | MEDLINE | ID: mdl-7339570

RESUMO

Subjects were exposed to an optical rotation of visual reafferences from hand movements. This is known to produce visuomotor adaptation. An experiment is reported where it also induced a perceptual aftereffect measured as a displacement of the apparent vertical and as an ocular cyclotorsion, both in the direction of the optical rotation. No correlation could be found between the two phenomena which can be considered as independent adaptive responses to the visuomotor conflict.


Assuntos
Movimentos Oculares , Ilusões/fisiologia , Ilusões Ópticas/fisiologia , Adaptação Ocular , Pós-Efeito de Figura , Percepção de Forma/fisiologia , Humanos , Orientação/fisiologia
15.
Exp Brain Res ; 51(2): 298-303, 1983.
Artigo em Inglês | MEDLINE | ID: mdl-6194009

RESUMO

Non-cerebellar afferents from visual relays to the vestibular nuclei (VN) of the cat have been re-evaluated with the use of the horseradish peroxidase technique. From our data it can be concluded that: (1) A monosynaptic projection from the nucleus reticularis tegmenti pontis to the VN can be excluded. (2) Monosynaptic projections from the superior colliculus and some of the pretectal nuclei (nucleus of the optic tract, olivary pretectal nucleus) to the nucleus prepositus hypoglossi may constitute polysynaptic visual afferents to the VN, which would account for the residual visual sensitivity of the VN neurons after cerebellar or inferior olivary lesions.


Assuntos
Vias Aferentes/fisiologia , Encéfalo/fisiologia , Nervo Hipoglosso/fisiologia , Nervo Óptico/fisiologia , Nervo Vestibular/fisiologia , Percepção Visual , Animais , Transporte Axonal , Gatos , Peroxidase do Rábano Silvestre , Sinapses/fisiologia , Visão Ocular , Córtex Visual/fisiologia
16.
Exp Brain Res ; 66(1): 41-8, 1987.
Artigo em Inglês | MEDLINE | ID: mdl-3582534

RESUMO

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.


Assuntos
Orelha Interna/fisiologia , Movimentos Oculares , Nervo Vestibular/fisiologia , Núcleos Vestibulares/fisiologia , Animais , Estimulação Elétrica , Ratos , Nervo Vestibular/citologia , Núcleos Vestibulares/citologia
17.
Exp Brain Res ; 81(1): 59-69, 1990.
Artigo em Inglês | MEDLINE | ID: mdl-2394231

RESUMO

The horizontal optokinetic reflex (OKN) was studied in cat, monkey and man under conditions of steady or stroboscopic illumination. In all species, there was an abrupt decrease in OKN gain for a given spatial displacement of the stimulus between two consecutive stroboscopic flashes. The upper limit of spatial displacement which preserved optimal OKN gain was independent of stimulus velocity and flash frequency. The value of this limit differed in the three species studied. In the cat, OKN gain was affected when the spatial displacement between two stimuli exceeded 0.55 degrees of visual angle. In monkey and man, these limits were 1.48 degrees and 2.87 degrees, respectively. When human subjects were asked to volontary track the stimulus, the limit value reached 4.3 degrees. This result is discussed in the context of the evolution of the smooth pursuit system and its contribution to optokinetic response.


Assuntos
Movimentos Oculares/fisiologia , Adulto , Animais , Gatos , Eletrodos Implantados , Eletroculografia , Humanos , Macaca mulatta , Pessoa de Meia-Idade , Nistagmo Fisiológico/fisiologia , Estimulação Luminosa , Especificidade da Espécie
18.
Exp Brain Res ; 116(1): 73-82, 1997 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-9305816

RESUMO

The effect of exposure to repeated angular velocity steps about the earth-vertical axis on the vertical vestibulo-ocular reflex (VOR) during onside pitch rotation was investigated in normal cats. By contrast with the VOR in the horizontal plane, the amplitude and duration of the vertical VOR did not progressively decrease throughout the repetition of velocity steps alternated in both directions. Instead, the amplitude of VOR decreased by about 40% during the very first trials in naive cats and then stayed unchanged with repeated stimuli. Habituation of the amplitude of the vertical VOR was observed when the velocity steps were always directed in the same direction. However, the duration of the vertical VOR did not show any signs of habituation. The habituation of the amplitude of the vertical VOR during unidirectional training was due to the progressive development of an initial inhibition of the VOR. This initial inhibition appeared much earlier during the bidirectional protocol, and was presumably responsible for the larger reduction in VOR amplitude observed during the very first session. These results support the model of two distinct mechanisms for VOR habituation, one producing an increasing inhibition of nystagmus, and the other depressing the response duration, and suggest that only the first mechanism is generated during repeated stimulation in the vertical plane. The low-frequency information provided by the velocity storage mechanism during onside pitch rotation, when the otoliths are positioned so they do not signal head tilt relative to gravity, could prevent a decrease in the overall response by the second mechanism.


Assuntos
Habituação Psicofisiológica/fisiologia , Reflexo Vestíbulo-Ocular/fisiologia , Animais , Gatos , Rotação
19.
Electroencephalogr Clin Neurophysiol ; 46(5): 521-30, 1979 May.
Artigo em Inglês | MEDLINE | ID: mdl-88340

RESUMO

The vestibulo-ocular response (VOR) was recorded during natural sleep in cats with chronically implanted electrodes. By using a small amplitude sinusoidal head rotation (11 degrees) peak-to-peak at 0.4 Hz) which elicited only slow compensatory eye movements, the VOR amplitude was found to decrease steeply (down to 40% or less) during slow-wave sleep. The phase of the VOR with respect to head position remained approximately constant. With a larger amplitude of sinusoidal rotation (320 degrees peak-to-peak at 0.05 Hz) the VOR response included nystagmus. During slow-wave sleep, nystagmus disappeared and the overall amplitude of the response decreased. Simultaneously, the phase of the eye response with respect to head position shifted by up to 90 degrees in advance. During paradoxical sleep, VOR disappeared in all cases and was replaced by randomly occurring bursts of rapid eye movements. These results are discussed in terms of a parametric control model of VOR.


Assuntos
Fases do Sono/fisiologia , Vestíbulo do Labirinto/fisiologia , Córtex Visual/fisiologia , Animais , Gatos , Eletroencefalografia , Neurônios Motores/fisiologia , Nistagmo Patológico/fisiopatologia
20.
Exp Brain Res ; 99(3): 441-54, 1994.
Artigo em Inglês | MEDLINE | ID: mdl-7957724

RESUMO

Bilateral surgical lesions of the flocculus or the nodulo-uvular lobes were performed in the cat. Effects of these lesions on optokinetic and optokinetic afternystagmus OKAN), vestibulo-ocular reflex (VOR), visual suppression, and adaptation and habituation of VOR were studied using an identical experimental protocol. After flocculectomy, all these functions were impaired, except for habituation. Long-term postoperative recordings only revealed a recovery of the suppression of VOR, suggesting a limited contribution of the flocculus to this function. After nodulo-uvulectomy, only habituation and OKAN were modified. When the lesion was restricted to part of the uvula, OKAN duration was decreased. For other lesions involving the uvula together with the nodulus and/or the lobules VII-VIII,OKAN duration was increased. Habituation was lost after destruction of the nodulo-uvular lobes. When this latter structure was damaged, the retention component of habituation was selectively impaired, sparing the acquisition. Additional lesions outside the vestibulocerebellum appeared necessary to suppress the two components. Comparison of results obtained after flocculectomy and after nodulouvulectomy confirms and extends to non-primate species the concept of a "differential control" of adaptation and habituation by distinct vestibulocerebellar structures.


Assuntos
Adaptação Fisiológica/fisiologia , Cerebelo/anatomia & histologia , Cerebelo/fisiologia , Vestíbulo do Labirinto/anatomia & histologia , Vestíbulo do Labirinto/fisiologia , Animais , Gatos , Estimulação Elétrica , Movimentos Oculares/fisiologia , Habituação Psicofisiológica/fisiologia , Plasticidade Neuronal/fisiologia , Nistagmo Optocinético/fisiologia , Estimulação Luminosa , Reflexo Vestíbulo-Ocular/fisiologia , Úvula/fisiologia
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