Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of bilateral saccular ablation on the asymmetry of vertical optokinetic after-nystagmus (OKAN) was studied in squirrel monkeys. No significant changes occurred in the initial slow-phase eye velocity (SPEV) or the time constant of the upward or downward OKAN first phase (OKAN-I) under various stimulus conditions. However, with a protracted downward stimulus, the maximum SPEV and the number of beats of the slow-phase-up OKAN second phase (OKAN-II) significantly increased. This increase should be the result from enhancement of the downward optokinetic input. In contrast, there was only minimal change in the slow-phase-down OKAN-II. Thus, the asymmetrical dominance of the vertical OKAN (dominance upward) remained the same after saccular deafferentation.
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PMID:The effect of saccular ablation on vertical optokinetic after-nystagmus in squirrel monkeys. 239 59

Ten years ago we proposed that the limitations on young infants' vision might be caused by an immature Y-pathway through the cortex, while their abilities might be mediated by an X-pathway to the cortex and by Y- and/or W-pathways to the superior colliculus and pretectum (Maurer & Lewis, 1979). Although that explanation was too simple overall, it fits well with what is known about asymmetrical optokinetic nystagmus, viz. the difficulty in eliciting OKN to patterns moving from the nasal field toward the temporal field. In this paper, we describe the development of symmetrical OKN, its alteration by early deprivation from cataract, and its physiological basis. We then suggest that, for primates, an explanation based on projections through the magnocellular versus parvocellular layers of the lateral geniculate nucleus may be more appropriate than one based on X-, Y-, and W-cells.
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PMID:Optokinetic nystagmus in normal and visually deprived children: implications for cortical development. 248 92

To correct compensatory head turn in twelve cases with congenital nystagmus, they were classified into two types according to the relative visual lines of both eyes to each other with respect to the sagittal axis of the head or the median plane of the body. One was termed the symmetrical pattern and the other was termed the asymmetrical pattern. In cases of the symmetrical pattern, a neutral zone exists in which the dominant eye in in the adducted position of gaze with esotropia and in the abducted position of gaze with exotropia. However, in the case of the asymmetrical pattern the neutral zone of the dominant eye is located in the abducted position of gaze with esotropia and in the abducted position of gaze with exotropia. Surgery was performed by shifting the dominant eye to the direction of the sagittal axis of the head in accordance with the degree of ocular deviation in the primary position. In asymmetrical pattern cares, both eyes were surgically shifted in parallel to the direction of the sagittal axis of the head without regard to the types of strabismus. The operation was based on the degree of compensatory head turn. We compared the surgical results the two types. In symmetrical cases, decreasing strabismus was disappointing compared to the head turn, while in asymmetrical cases decreasing head turn was disappointing as compared to strabismus. From these results surgery should be confined to the dominant eye in symmetrical cases, taking as the basis for operation the degree of head turn and not the ocular deviation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Surgical treatment of torticollis in cases of congenital nystagmus with strabismus]. 261 Jan 64

A quantitative study of horizontal and vertical optokinetic nystagmus (OKN) and optocollic reflex (OCR) has been performed in the pigeon using the search-coil technique. The reflexes were analysed in response to either velocity steps or sinusoidal stimulation. Results show that: 1. In response to a velocity step stimulation, the slow phase velocity of both OKN and OCR increases gradually to reach a steady state level. When the stimulation stops in the dark, After Responses (OKAN-I, OKAR-I) occur. Time constants of the OKN charge (or OCR charge) and of the After Responses are lower for vertical than for horizontal responses. 2. In the free-head condition, both the head and the eye display a synchronized nystagmus which add their effects. However, the head reflex (OCR) accounts for about 80-90% of the entire linear gaze response (head + eye), except for the vertical steady state responses which are wholly accomplished by the head (OCR). 3. Both closed-loop and open-loop gains of steady state responses are higher for horizontal than for vertical reflexes. Vertical OCR, horizontal OKN and vertical OKN show properties of binocular integration, the response gain being higher for binocular than for monocular stimulations. By contrast, the horizontal OCR shows little binocular integration but displays a higher response gain for monocular stimulation, compared to horizontal OKN. 4. The horizontal OKN elicited by both monocular and binocular stimulation is asymmetrical, the gain being higher when the eye is driven by a temporo-nasal stimulation. In contrast, both vertical OKN and vertical OCR are practically symmetrical. 5. While both the gain of horizontal OKN and its linear range (up to 20 degrees/s) are improved when the head is free (gaze gain close to 1 up to 40 degrees/s), the vertical OKN and the vertical OCR have similar gain profiles and similar domains of linearity (up to 10 degrees/s). 6. In response to increasing the frequency of a sinusoidal stimulation at constant peak velocity, all the reflexes display a drop in gain and a strong increase of phase lag. The phase increase is greater for horizontal than for vertical reflexes. On the other hand, both gain and phase are higher for OCR than for OKN, both in the horizontal plane as well as in the vertical plane. 7. For sinusoidal stimulations, when the peak velocity (PV) is increased at a constant frequency (0.03 Hz), nonlinearities appear (drop in gain, phase increase) both for OKN and OCR.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Stabilizing gaze reflexes in the pigeon (Columba livia). I. Horizontal and vertical optokinetic eye (OKN) and head (OCR) reflexes. 337 39

Conventional vestibular rotation testing with the head centered on the axis stimulates the semicircular canals evoking compensatory eye movements. If the head is placed forwards of the axis in an eccentric position the otoliths are also stimulated by a tangential linear acceleration acting laterally to the skull. In normal subjects the additional otolithic stimulus evokes compensatory eye movements with a higher gain than with head centred, particularly for high frequency (greater than 0.1 Hz) stimuli. The responses with head centred and eccentric in various patients with known/suspected neuro-otological abnormalities have been compared. Patients with vestibular neurinectomies who have asymmetrical head centred responses showed greater asymmetry with head eccentric at higher stimulus frequencies. Some patients with cerebellar lesions showed abnormally enhanced or depressed and asymmetrical responses with head eccentric in comparison with head centred responses, which could be normal. The enhancing effects could be specific to low frequency stimuli. All patients who showed abnormal responses with head eccentric also had positional nystagmus provoked by the gravity acceleration vector when the head was tilted laterally. The direction of the positional nystagmus with respect to the gravity vector was not necessarily the same as the direction of the effect on eye movements of lateral acceleration during eccentric oscillation. Patients with benign paroxysmal vertigo or chronic linear vertigo in whom otolithic abnormalities are suspected were not found to have abnormal responses with head eccentric. We conclude that this method of testing may be useful in elucidating pathophysiology but is not a decisive clinical test for the presence of disordered otolith function.
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PMID:Testing the vestibular-ocular reflexes: abnormalities of the otolith contribution in patients with neuro-otological disease. 365 7

We report the oculographic findings in a family whose members have a dominantly inherited, early onset, non-progressive syndrome which includes spontaneous upbeating nystagmus and mild cerebellar ataxia associated with cerebellar vermian atrophy seen on magnetic resonance scanning. Eye movements recorded with electro-oculography and a magnetic scleral search coil revealed severely impaired horizontal and vertical smooth pursuit, optokinetic nystagmus and visual-vestibular interaction, symmetrical horizontal but asymmetrical vertical vestibulo-ocular reflex, and normal saccades. The midline cerebellum appears to be essential for both horizontal and vertical visual tracking and visual modification of the vestibulo-ocular reflex in man.
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PMID:Eye movement abnormalities in a family with cerebellar vermian atrophy. 372 75

It has frequently been reported that the spontaneous ocular oscillation in congenital nystagmats is less intense for near viewing than during distance fixation. The reason for this effect was sought, and the influences of monocular adduction, convergence and accommodation acting separately and synergistically were assessed. The frequent assumption that nystagmus intensity (amplitude and frequency) is determined by convergence angle (either symmetrical or asymmetrical) was confirmed, and it was found that binocular viewing was not necessary. An identical effect on nystagmus intensity could be created for distance fixation by the use of base-out prisms, and these were prescribed for constant wear in two congenital idiopathic nystagmats. Although nystagmus intensity was constantly reduced, no concomitant increase in binocular contrast sensitivity or Snellen visual acuity occurred.
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PMID:The elucidation and use of the effect of near fixation in congenital nystagmus. 382 71

Horizontal and vertical eye movements were recorded in 16 human albinos with a scleral search coil technique. Spontaneous nystagmus, responses to target steps, voluntary pursuit and optokinetic nystagmus (OKN) were assessed, including the effects of selective stimulation of the nasal or temporal halves of the retina. The results suggest a subdivision of albinos into three classes of oculomotor behaviour. Class I (n = 11) is characterized by vigorous spontaneous nystagmus (of the pendular unidirectional jerk or bidirectional jerk type), the absence of true horizontal OKN but the presence of the ability to control the direction of gaze in an imprecise way. In Class II (n = 2) there is a vigorous unidirectional jerk nystagmus which reverses in direction spontaneously or as a result of visual stimulation. Moving stimuli typically elicited inverted pursuit, the smooth eye movements having a direction opposite to that of the stimulus movement. Class III (n = 3) is characterized by very little or no spontaneous nystagmus and virtually normal oculomotor responses. Only pursuit of motion in the temporal direction, projected onto the temporal half retina, was defective. In all three classes, vertical eye movements were disturbed much less than horizontal. Anomalous visual projections (confirmed in all subjects by asymmetrical monocular visual evoked cortical potentials) are a likely basic cause underlying the oculomotor instability, but the large intersubject differences show that the eventual consequences of misrouting and secondary adaptations can vary widely among subjects.
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PMID:The oculomotor behaviour of human albinos. 397 93

Vertical optokinetic nystagmus (OKN) i.e., OKN in the sagittal plane, was asymmetrical in the monkey when it was induced with animals lying on their sides in a 90 degrees roll position. In typical monkeys the slow phase velocity of downward OKN (slow phases up) increased proportionally with stimulus velocity at close to unity gain to about 60 degrees/s and saturated at about 100 degrees/s. Upward OKN (slow phases down) increased with close to unity gain only to about 40 degrees/s and saturated at about 60 degrees/s. The slow phase velocity of upward OKN was usually irregular and its frequency was lower than that of downward or horizontal OKN. Upward and downward optokinetic after-nystagmus (OKAN) were also asymmetrical. Upward OKAN was weak or absent and when present it usually saturated at 10 degrees/s. Downward OKAN was stronger, increasing with a gain of about 0.7 with regard to stimulus velocity to a saturation velocity of about 50-60 degrees/s. This was usually about 10-30 degrees/s less than the saturation velocity of horizontal OKAN. The weak or absent upward OKAN indicates that stored activity related to slow phase eye velocity contributes little to the production of upward OKN. In agreement with this, there was little or no slow rise in slow phase velocity to a steady state level during upward OKN. Instead eye velocity rose to its peak velocity at the onset of stimulation. The lack of stored velocity information is probably largely responsible for the differences in regularity, gain and frequency between upward and downward OKN. Vertical vestibular nystagmus was induced by rotating monkeys in darkness with steps of velocity about a vertical axis, while they were lying on their sides in a 90 degree roll position. The velocities of the initial upward and downward slow phases were approximately equal. Gains of the vertical VOR ranged from about 0.5 to 0.98 for stimuli up to 150 degrees/s. Despite equivalent initial gains for upward and downward nystagmus, the vertical VOR was asymmetrical in that downward nystagmus had a higher frequency and generally lasted longer than upward nystagmus. Time constants of downward nystagmus (slow phases up) were about 15 s on average and were similar to those of horizontal nystagmus. Mean time constants of upward nystagmus (slow phases down) were about 8 s. This is only slightly longer than the average time constant of afferent activity in the semicircular canal nerves induced by steps of velocity.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Vertical optokinetic nystagmus and vestibular nystagmus in the monkey: up-down asymmetry and effects of gravity. 660 54

Binocular and monocular optokinetic nystagmus (OKN) was examined with EOG recordings in 26 visually impaired children with neurological disorders, aged 2.5 months to 15 years. Spontaneous and/or latent nystagmus, complicating the assessment of OKN, was seen in 73% of the children. Binocular OKN in 21 patients with positive visual functions was symmetrical in 5 cases, asymmetrical in 12 cases and could not be elicited in 4 patients. Monocular OKN was nearly always asymmetrical, with usually a superiority of the temporal-to-nasal (TN) components. Five blind children, 4 of them cortically blind, showed positive binocular and monocular OKN, suggesting that neural control of OKN in humans may be at least partly independent of the cortex. This, together with results from some of the sighted patients, indicates that in humans, cortical and subcortical contributions to OKN, and particularly to monocular nasal-to-temporal (NT) OKN, may be more complicated than had been thought.
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PMID:Optokinetic and spontaneous nystagmus in children with neurological disorders. 663 24


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