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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some characteristics of the horizontal optokinetic nystagmus (OKN) have been studied in the pigeon using monocular and binocular stimulations. The OKN is asymmetrical, temporal to nasal stimulation eliciting a larger response than a nasal to temporal one. The role of the accessory optic system (AOS) was studied by means of unilateral or bilateral lesions of the primary relays, nuclei ectomamillaris (nEM) and superficialis synencephali (nSS). Results show the existence of a synergy between nEM and nSS on the same side and between nEM and nSS on opposite sides, whereas each nucleus has an inhibitory effect upon its contralateral homologue. Some evidence was obtained which suggests the existence of an ipsilateral retinal projection to the nEM.
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PMID:[Horizontal optokinetic nystagmus in the pigeon: role of accessory optical system]. 678 74

Normative data were obtained for 156 pre-school children's performances on measures of muscle tone, muscle co-contraction, standing balance, prone extension posture, flexion supine posture, asymmetrical tonic neck reflex, and postrotary nystagmus. Regression analysis indicated that these combined variables accounted for only 13.5 percent of the variance of postrotary nystagmus of 145 four year olds. However, if the data are examined only for children exhibiting nystagmus that is lower than 1 standard deviation below the mean, then these variables account for 50 percent of the variance of nystagmus. Prone extension posture, standing balance-eyes closed, and muscle tone account for 37 percent of the variance within this low-nystagmus population. These results are considered in light of the authors' previous studies demonstrating that, in learning-disabled children, vestibular-proprioceptive measures can be used clinically to predict which children will respond to sensory integration therapy with changes in postrotary nystagmus. These changes, according to sensory integration theory, reflect positive responses to therapy.
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PMID:Vestibular-proprioceptive functions in 4 year olds: normative and regression analyses. 684 72

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.
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PMID:Effects of unilateral flocculus lesions on vestibulo-ocular responses in the cat. 686 65

One hundred patients with dissociated vertical divergence (DVD) have been followed up for an average of 7.3 years. In contrast to some other reports, none of them has worthwhile binocular vision. There has been a constant association with nystagmus, often manifest, and the DVD has always been noted later than the nystagmus. In no case has the degree of DVD decreased significantly with age. The dissociation has only rarely caused a serious cosmetic problem, and then it has been markedly asymmetrical and has been improved by combined superior rectus recession and Faden procedure. DVD can simulate inferior oblique overactions, but is more commonly associated with an A phenomenon, and can be distinguished by careful cover/uncover testing. The common occurrence of associated congenital defects, especially of the central nervous system, is noted.
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PMID:Natural history and associations of dissociated vertical divergence. 694 95

Oculomotor and oculovestibular functions in a patient who had undergone a left hemispherectomy were examined under a variety of visual and vestibular stimuli. The main findings were an inability to hold left eccentric gaze, resulting in gaze-evoked nystagmus to that side; inaccurate saccades to the right; defective smooth pursuit to the left; asymmetrical vestibulo-ocular responses (VOR) in the dark due to the interaction of the VOR with the "spasticity of conjugate gaze", decreased gain of the visuo-vestibulo-ocular reflexes to both sides, more marked to the right, when rotated fixating on a stationary wall target or the environment, due to abnormal smooth and optokinetic systems; and failure to inhibit the VOR when rotated to the left with visual fixation.
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PMID:Oculomotor and oculovestibular functions in a hemispherectomy patient. 696 22

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.
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PMID:The role of the flocculus in vestibular compensation after hemilabyrinthectomy. 709 79

The authors describe a patient suffering from torticollis with an eccentric neutral point of relative rest caused by a congenital nystagmus (rotation to the left for long-range vision and to the right for close-range vision - nystagmus alternans); the torticollis is not aggravated in close-range vision by an asymmetrical Anderson-Kestenbaum operation at a suitable range (asymmetrical correction of the torticollis for long-range vision by exploiting the range of fusion into divergence). Surgical alternatives are discussed and trigonometric relations are correlated with clinical experience (for torticollis with binocular functions). Torticollis without binocular functions is discussed in brief.
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PMID:[Numerical reflections concerning alternating torticollis with nystagmus and binocular functions (author's transl)]. 723 Jun 71

Eye movements recorded with the magnetic-field search coil technique from six cats raised in an 8 Hz stroboscopically illuminated environment were found to be normal with the exception of fixation and optokinetic nystagmus. Fixation eye movements were characterized by a 4-5 Hz conjugate pendular nystagmus superimposed on a wandering drift. Optokinetic nystagmus was very asymmetrical on monocular tests. Depriving the oculomotor system of experience differentially effects fixation and smooth pursuit.
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PMID:Oculomotor changes in cats reared without experiencing continuous retinal image motion. 725 Feb 69

A mother and son suffer from hemiplegic migraine with onset in childhood. Both have nystagmus which has not changed for many years, but the date of onset is uncertain. They have an asymmetrical tremor, clinically indistinguishable from essential tremor. Neuroophthalmological examination revealed inability to produce smooth pursuit, gaze-paretic nystagmus, rebound nystagmus, failure of fixation suppression of the vestibuloocular reflex both horizontally and vertically, and low gain of the optokinetic system. These abnormalities, confirmed by electrooculography, are commonly seen in disease of the cerebellum and brainstem. Treatment with propranolol and pizotyline lessened the number of episodes of hemiplegia and improved the tremor. Hemiplegic migraine has been reported in association with nystagmus, retinal degeneration, deafness, and ataxia in varying combinations in three other families with autosomal dominant inheritance. These associated neurological manifestations likely represent system degenerations rather than the effect of repeated ischemia imputable to the migraine itself. The syndrome of hemiplegic migraine, tremor, and ocular smooth pursuit system disorder seen in this family appears to be inherited as a single autosomal dominant trait, although more than one autosomal dominant gene may be involved.
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PMID:An autosomal dominant syndrome of hemiplegic migraine, nystagmus, and tremor. 743 78

1. For horizontal eye movements, previous observations led to the hypothesis that the legendary neural integrator necessary for correct gaze holding, adequate vestibuloocular reflex (VOR), and optokinetic nystagmus, was located in the region of the complex formed by the nucleus prepositus hypoglossi (NPH) and the medial vestibular nucleus (MVN). 2. The aim of the present study was to test the respective contributions of the NPH, of the rostral part of the MVN, which contains most second-order vestibular neurons, and of the central part of the MVN to the horizontal integrator. 3. An injection of muscimol was used to inactivate each of these three zones in the cat's brain. Muscimol is a gamma-aminobutyric acid (GABA) agonist. By binding to GABAA receptors, it induces a hyperpolarization of the neurons that nullifies their activity. Muscimol was injected into the brain stem of the alert cat through a micropipette by an air pressure system. 4. The search coil technique was used to record spontaneous eye movements and the VOR induced by rotating a turntable at a constant velocity. VOR was analyzed by a new method: transient analysis of vestibular nystagmus. 5. A unilateral injection of muscimol into the NPH induced a bilateral gaze-holding failure: saccades were followed by a centripetal postsaccadic drift. A vestibular imbalance was also present but it was moderate and variable. The VOR responses were distorted drastically. Through transient analysis of vestibular nystagmus, that distortion was revealed to be due more to a failure of the neural integrator than to an alteration of the vestibular input to the neural integrator. The responses to a rotation either toward the injected side or in the opposite direction were asymmetrical. The direction of that asymmetry was variable. 6. A unilateral injection of muscimol into the rostral part of the MVN caused a vestibular imbalance: in complete darkness, a nystagmus appeared, whose linear slow phases were directed toward the side of injection. 7. A unilateral injection of muscimol into the central part of the MVN induced a syndrome where a severe bilateral gaze-holding failure was combined with a vestibular imbalance. In the light, saccades were followed by a bilateral centripetal postsaccadic drift. In complete darkness, a nystagmus was observed, whose curved slow phases were directed towards the side of injection. The VOR responses were distorted drastically. Here again, that distortion was revealed by our analysis to be due more to a failure of the neural integrator than to an alteration of the vestibular input to the neural integrator.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of muscimol microinjections into the prepositus hypoglossi and the medial vestibular nuclei on cat eye movements. 798 36


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