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At least 703 records · Page 39Linked to original sources
PubMed1979

Roving eye movements with bilateral symmetrical lesions of the thalamus.

Typical roving eye movements (pendular deviations of the bulbi) were observed in a 41-year-old patient with bilateral symmetrical softenings in the anterior thalamic region. They constantly appeared after lid closure with a mean latency of 7.3 sec. The mean frequency was 0.25 cps, the mean amplitude 30 degrees. The phenomenon of roving eye movement is discussed with regard to the supranuclear structures regulating binocular eye movements.

Adult↗
PubMed1993

Influence of stimulus size and contrast on the temporal parameters of saccadic eye movements: implications for road traffic.

Saccadic eye movements are required for the recognition of peripheral objects in road traffic. Their latencies largely determine reaction time in emergency situations. The aim of this study was to investigate the influence of stimulus and surround parameters on the temporal characteristics of saccadic eye movements under conditions of object size, contrast and luminance corresponding to nighttime traffic. Square stimuli of 1 degree or 5 degrees size were presented under an eccentricity of 5 degrees and 15 degrees. The luminance of the surround was 4 x 10(-4) cd/m2 and 1 cd/m2. More than approx. 2,000 saccades of 7 normal subjects were registered and evaluated with respect to the latency, maximal velocity, and frequency of secondary saccades. At high stimulus contrast, latency approaches a minimum of approx. 200 ms. Latency increases with decreasing contrast up to maximal values of more than 600 ms. Transforming the contrast values into a relative decibel scale shows that this increase in latency occurs at significantly higher relative contrast values under scotopic as compared with photopic conditions. Our results demonstrate that an overall latency of 200-300 ms is not adequate for the assessment of accidents, especially under the stimulus conditions of nighttime traffic.

Adult↗
PubMed1977

Eccentric head positions reveal disorders of conjugate eye movement.

The effect of head position on conjugate horizontal gaze was studied in healthy adults, in patients with multiple sclerosis without eye movement signs, and in patients with downbeat nystagmus indicative of low brain stem lesions. Displacements of gaze from primary position to 30 degrees left and right were recorded using the electro-oculogram, with the head in the primary position, and turned voluntarily to the left and right (in yaw). The quality of eye movements was noted and peak velocities of saccades were measured. The head turning test trebled the incidence of abnormal eye movements found in the multiple sclerosis patients and increased it by tenfold in the patients with downbeat nystagmus. Disorders of eye movement were also found in approximately 20--30% of healthy subjects tested. Weakness of abduction was the most common eye movement defect and appeared to be posterior internuclear ophthalmoplegia. A hypothesis is made which unifies the theoretical explanations of anterior and posterior internuclear ophthalmoplegia. The most likely cause of the disorders of eye movement observed is vertebrobasilar ischaemia induced by stretching and compression of the vertebral arteries during eccentric head posture.

Adult↗
PubMed2006

Looking for answers: eye movements in non-visual cognitive tasks.

It is not known why people move their eyes when engaged in non-visual cognition. The current study tested the hypothesis that differences in saccadic eye movement rate (EMR) during non-visual cognitive tasks reflect different requirements for searching long-term memory. Participants performed non-visual tasks requiring relatively low or high long-term memory retrieval while eye movements were recorded. In three experiments, EMR was substantially lower for low-retrieval than for high-retrieval tasks, including in an eyes closed condition in Experiment 3. Neither visual imagery nor between-task difficulty was related to EMR, although there was some evidence for a minor effect of within-task difficulty. Comparison of task-related EMRs to EMR during a no-task waiting period suggests that eye movements may be suppressed or activated depending on task requirements. We discuss a number of possible interpretations of saccadic eye movements during non-visual cognition and propose an evolutionary model that links these eye movements to memory search through an elaboration of circuitry involved in visual perception.

Analysis of Variance↗
PubMedDate not supplied

On automatic diagnosis of pathological saccadic eye movements.

A syntactic technique is described for the recognition of saccadic eye movements to distinguish normal saccades from those distorted by brain stem lesions. A digitalized eye movement signal is transformed into a sequence of symbols. Eye movements are then found from this sequence by using a parser. This recognition method appropriately enlarged could be applied as a classifier of saccades to aid in diagnosis.

Algorithms↗
PubMed2005

The role of tropomyosin-related kinase receptors in neurotrophin-induced rapid eye movement sleep in the cat.

The microinjection of nerve growth factor and neurotrophin-3 into the rostro-dorsal pontine tegmentum of the cat evokes a state that is comparable to naturally-occurring rapid eye movement sleep. Using two experimental paradigms, we tested the hypothesis that neurotrophin high-affinity receptors (trkA and trkC, tropomyosin-related kinase A and C, respectively) mediate this effect. First, trk and fos immunohistochemistry were combined to determine whether tyrosine kinase receptor-containing neurons in the dorsal pontine tegmentum are active in cats that exhibit long-lasting periods of rapid eye movement sleep following the local microinjection of nerve growth factor. During approximately two hours of recording, nerve growth factor-treated cats spent 59.8% of the time in a rapid eye movement sleep-like state; vehicle-injected (control) animals remained in quiet wakefulness and non-rapid eye movement sleep. Whereas control and nerve growth factor-treated cats exhibited a similar mean number of trkA- and trkC-immunoreactive neurons in the dorsal pontine tegmentum, the number of trkA- and trkC-immunoreactive neurons that expressed Fos, i.e. double-labeled cells that are presumably activated, was significantly larger in cats that were injected with nerve growth factor. Axon terminals contained tyrosine kinase receptor immunoreactivity in this region; many were apposed to Fos-immunoreactive neurons. In addition, patterns of tyrosine kinase receptor and Fos immunoreactivity similar to those observed in nerve growth factor-injected cats were present, in conjunction with long-lasting rapid eye movement sleep, following the microinjection of carbachol into the dorsal pons. In a second series of studies, nerve growth factor or neurotrophin-3 was injected alone or after K-252a, a blocker of tyrosine kinase receptors, into the rostro-dorsal pontine tegmentum. Nerve growth factor or neurotrophin-3 alone produced, with a mean latency of 4 min, a rapid eye movement sleep-like state. However, neurotrophin injections preceded by K-252a were not effective in inducing rapid eye movement sleep. These results indicate that the activation of trkA and trkC receptors in neurons in the pontine tegmentum is responsible, at least in part, for the rapid eye movement sleep-inducing effect of nerve growth factor and neurotrophin-3. Furthermore, the data suggest that these neurotrophins are capable of acting both pre- and postsynaptically to activate pontine neurons that are involved in the generation of rapid eye movement sleep.

Analgesics, Non-Narcotic↗
PubMed2006

Eye movements coordinated with steering benefit performance even when vision is denied.

When driving along a winding road, eye movements and steering are tightly linked. When approaching a bend, the driver looks across to the inside kerb (the tangent point) some time before turning the steering wheel. All drivers we have tested show this optimal coordination, without which driving is impaired. An intriguing question is how much of the benefit for steering arises just from moving the eyes in this coordinated way (ahead of steering and in the same direction), and how much from the visual information that the eyes move to acquire, in this instance the foveated tangent point. This can be answered by dissociating the two, by reducing visibility of the road ahead (and crucially of the tangent point) to a level at which drivers might or might not choose to move their eyes but, if they do, will not gain the information they seek. Twenty subjects repeatedly drove a simulated stage of the World Rally Championship. With full visibility, they exhibited the usual coordination of eye movements and steering. Subsequently, visibility was reduced on the left hand side. Drivers who persisted in making eye movements coordinated with steering to the left, despite the fact that they could no longer see the tangent point on that side, performed better than drivers who under the identical conditions did not look to the left. This confirms that the making of coordinated eye movements itself benefits steering, even when the eye movements do not yield the visual information sought.

Adult↗
PubMed1986

Visually stimulated saccadic eye movements in patients treated with lithium.

Saccadic eye movements were stimulated with the aid of 11 light spot stimuli, 10 of which were arranged at 3 degrees, 6 degrees, 9 degrees, 12 degrees, and 15 degrees to the left and right of the central stimulus. The parameters average and maximal eye movement velocity and latency were precisely investigated. 19 patients averaging 6.6 years on lithium prophylaxis were compared with 23 healthy controls. Significant differences between the two groups could not be found at this level of function.

Adult↗
PubMed2001

Diurnal variation of eye movement and heart rate variability in the human fetus at term.

To elucidate diurnal variations in eye movement and fetal heart rate (FHR) variability in the term fetus, we observed these two parameters continuously for 24 h, using real-time ultrasound and Doppler cardiotocograph, respectively. Studied were five uncomplicated fetuses at term. The time series data of the presence and absence of eye movement and mean FHR value for each 1 min were analyzed using the maximum entropy method (MEM) and subsequent nonlinear least squares fitting. According to the power value of eye movement, all five cases were classified into two groups: three cases in the large power group and two cases in the small power group. The acrophases of eye movement and FHR variability in the large power group were close, thereby implying the existence of a diurnal rhythm in both these parameters and also that they are synchronized. In the small power group, the acrophases were separated. The synchronization of eye movement and FHR variability in the large power group suggests that these phenomena are governed by a common central mechanism related to diurnal rhythm generation.

Adult↗
PubMed2004

Eye movements of goldfish depending on the relationship between acceleration vector and otolith organ.

Prior experiments demonstrated that the acceleration deviating 15 degrees to the right (left) from the longitudinal body axis could not produce vertical eye movement in left (right) eye of the goldfish. From these results, we expected that vertical eye movement of goldfish for the acceleration perpendicular to the longitudinal body axis might different between right and left eye. However, in this experiments, there were no clear difference in magnitude of vertical eye movements for the acceleration shifted 15 degrees around the left-right body axis. On the other hand, the response of right eye was larger than that of left eye for the acceleration applied from left to right of the body. These results suggest that stimulation from medial to lateral and lateral to medial of the otolith organ has different effect on vertical eye movement in each eye of goldfish.

Acceleration↗
PubMed2000

Oculocentric coding of inhibited eye movements to recently attended locations.

Results are reported for experiments that examined eye movements directed toward recently cued objects. In 1 experiment participants were slower to initiate saccades toward the earlier location of an object that had been cued, even though the cued object had subsequently moved away from that location. Other experiments involved exploring the reference frame within which the inhibited eye movements are encoded. These experiments revealed that the eye movement that is inhibited is encoded in an oculocentric-rather than an environmental-reference frame. However, simple detection as indexed by manual keypress responses is encoded in an environmental reference frame. The results have implications for inhibition of return, for the link between eye movements and attention, and for the nature of the spatial reference frames in which both covert and overt movements of attention are encoded.

Adult↗
PubMedDate not supplied

Disconjugate eye movements during electronstagmographic testing in patients with known central nervous system lesions.

A tacit assumption underlying current ENG testing is that the eyes move conjugately. However, considering the intricate neuroanotomical pathways within the ocular motor system in addition to the elaborate vestibulo-ocular connections, we think it reasonable that disconjugate eye movements may result with certain CNS lesions. Recently we have employed independent eye movement measuring techniques in order to assess the movement of each eye separately during our ENG valuations. The preliminary work has revealed that disconjugate eye movements occurred even with extra-axial lesions which spared the medial longitudinal fasciculus. These data may be valuable for the neurotologist with regard to differential diagnosis and prescription of a treatment plan for the patient. The eye movement patterns of patients with confirmed CNS lesions and other interesting findings are presented.

Adult↗
PubMedDate not supplied

Dynamic details of disparity convergence eye movements.

Classically, the primary tool for quantifying the dynamics of vergence and other eye movements has been the main sequence. The main sequence is a plot of peak velocity versus response amplitude and is particularly useful for comparing the dynamics of a large number of eye movements over a range of response amplitudes. However, the main sequence represents only the equivalent first-order behavior of a response and does not describe its dynamics in detail. Since the main sequence is based on only two points on the dynamic trajectory, it is sensitive to measurement artifacts and noise. A new methodology is presented which quantifies the equivalent second-order dynamics of eye movements using a larger region of the transient response. These new indexes were applied to vergence eye movements and were found to differentiate between subtle, but important differences in movement dynamics.

Biomedical Engineering↗
PubMed1983

Sex differences and eye movements.

This study was designed to examine sex differences in eye movements. Recordings were made from 28 right-handed students (15 males and 13 females). Both the number and direction of eye movements elicited during a 10-second time interval following questions presumed to elicit spatial or verbal processing and which had neutral or affective content were recorded. The results showed that (1) global oculomotor activity was significantly higher for females than for males; (2) verbal questions elicited significantly more responses than spatial ones and emotionally charged questions more movements than neutral ones; (3) the proportion of movements to the right was higher than that to the left for females, whereas the reverse was observed in males, and (4) whatever the nature of the question, females tended to look right whereas males tended to look left. Despite some divergent results concerning the presumed power of questions to elicit right or left hemisphere activity, it seems that lateral eye movements show a coherent pattern provided that sex differences are taken into account.

Adult↗
PubMed1995

Eye movement patterns in hemianopic dyslexia.

Homonymous parafoveal field loss impairs reading at the visual-sensory level. To elucidate the role of parafoveal visual field in reading, reading eye movements were recorded, by means of an infra-red registration technique, in 50 patients with homonymous hemianopia and visual field sparing ranging from 1 degree to 5 degrees; for comparison, a group of 25 normal subjects was studied. The degree of reading impairment in patients was found to depend on the extent of visual field sparing. Patients with right-sided loss of parafoveal visual field were more impaired than patients with left-sided loss. Eye movement reading patterns paralleled this observation. Left-sided field loss mainly impairs return eye movements to the beginning of a line, while right-sided field loss is characteristically associated with prolonged fixations times, reduced amplitudes of saccades to the right, and many regressive saccades. The analysis of the durations of fixations, and the amplitudes of saccadic eye shifts to the right, and their mutual dependencies, suggests that the perceptual window ('reading span') is altered: its spatial size is reduced, while its temporal extent is increased. The analysis of reading eye movements in 20 patients, who were treated for their hemianopic reading disorder, revealed, in part, a normalization of the eye movement pattern after treatment, indicating that the lost parafoveal field region can be successfully substituted by oculomotor adaptation. Our observations underline the importance of the parafoveal visual field for reading and support the hypothesis of a serial interplay between sensory-perceptual and cognitive factors in reading. Furthermore, reading eye movements appear to be guided primarily by parafoveal information processing; however, eye movement patterns show relative plasticity with respect to 'local' adaptation when the parafoveal field region is lost. The adaptation can best be explained by a change of the perceptual window which appears to be guided mainly by top-down influences. As to the brain lesion which may be responsible for the lack of effective oculomotor compensation, damage to the occipital white matter appears the most crucial condition because it may disconnect visual cortical areas, and interrupt subcortical-cortical connections which are part of a neural network subserving directed visual attention and associated saccadic eye shifts.

Adolescent↗
PubMed1982

Eye movements and vestibular-nerve responses produced in the squirrel monkey by rotations about an earth-horizontal axis.

The eye movements produced by constant-speed rotations about an earth-horizontal axis (EHA) are similar in the alert squirrel monkey to those observed in other species. During EHA rotations, there are persistent eye movements, including a nonreversing nystagmus at lower rotation speeds and either a direction-reversing nystagmus or sinusoidal eye movements at higher rotation speeds. Horizontal eye movements are produced by "barbecue-spit" (yaw) rotations, vertical eye movements by "head-over-heels" (pitch) rotations. The responses can be viewed as composed of a bias component, reflected in the nonreversing nature of the nystagmus, and a cyclic component, reflected in the periodic modulation of slow-phase eye velocity as head position varies. Vestibular-nerve recordings in the barbiturate-anesthetized monkey indicate that neither semicircular-canal nor otolith afferents give rise to a directionally specific dc signal which can account for the bias component. Apparently the appropriate dc signal has to be constructed centrally from a sinusoidal or ac peripheral input. The otolith organs are a likely source of this peripheral input, although contributions from the semicircular canals and from somatosensory receptors must also be considered. Our results suggest that the directional information required to distinguish rotation direction, rather than being contained in the discharge of individual otolith afferents, is encoded across a population of afferents. Possible sources of such information are the phase differences in the sinusoidal responses of otolith afferents differing in their functional polarization vectors.

Acoustic Maculae↗
PubMed2006

Disruption of reflexive attention and eye movements in an individual with a collicular lesion.

The superior colliculus (SC) plays a central role in the control of saccadic eye movements and has also been implicated in control of covert spatial attention. While there is a growing body of evidence from studies of awake behaving primates that supports these proposals, direct evidence from humans has been sparse. In the present study we tested a patient with thiamine deficiency and a lesion of the SC, who performed both eye movement tasks (prosaccades and antisaccades, with or without a gap) and a covert spatial attention task assessing inhibition of return (IOR). For eye movements, the gap effect was disrupted, and abnormal saccade metrics occurred, with reflexive eye movements being disrupted moreso than voluntary eye movements. Each of these effects resolved coincident with thiamine treatment. The covert attention task revealed a complete absence of IOR. The unequal disruption of voluntary and reflexive eye movements supports the idea that oculomotor responses can be generated in an independent fashion by frontal cortical and lower level neural systems. The role of the SC and other structures in these orienting processes is discussed.

Attention↗
PubMed1984

Eye movements, afterimages and monocular rivalry.

The eye-movement/afterimage theory of "monocular rivalry" (MR) between gratings was tested and strongly supported. In three experiments perceptual dominance of vertical or horizontal components of the pattern and fluctuations in perceived contrast of a single grating were shown to depend on the nature of the preceding shift in fixation position in the manner predicted by the theory. In a fourth experiment the angular selectivity of these fluctuations was eliminated, as predicted, when appropriate eye movements were made. Fixation-contingent fluctuations became equally strong for 15 degrees and 90 degrees angles. Taken together with data on afterimages, the results appear to resolve most of the problems recently raised against the theory.

Afterimage↗