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At least 613 records · Page 34Linked to original sources
PubMed1983

Eye movement disorders in multiple sclerosis and optic neuritis.

Horizontal saccadic and smooth pursuit eye movements were studied in 84 patients with multiple sclerosis (MS) and 21 patients with optic neuritis (ON). The MS patients were clinically classified as 'definite', 'probable', or 'possible'; subclinical eye movement disorder was found in 80 per cent of the definite, 74 per cent of the probable and 60 per cent of the possible category. Five of the ON patients (25 per cent) showed a subclinical eye movement deficit; these 5 were young patients with a recent history of ON. In a group of 27 MS patients with symptoms of spinal cord involvement only, 14 showed subclinical oculomotor disorder indicating the involvement of cerebral structures in the demyelination process. A study of the correlation between specific eye movement parameters and results of visual evoked response (VER) tests revealed that saccadic latency or smooth pursuit abnormalities are not correlated with prolonged VER latencies (P-100 peak latency). This indicates that lesions beyond the primary visual pathway contribute substantially to both parameters of oculomotor dysfunction. A significant correlation was found between prolonged saccadic latency and smooth pursuit deficit. An explanation for this finding based on functional aspects of the saccadic and smooth pursuit systems and their mutual interaction is presented. The occurrence of internuclear ophthalmoplegia (INO) is significantly related to an increase of saccadic latency. This finding indicates that demyelination in the patients manifesting INO may not be restricted exclusively to one or both medial longitudinal fasciculi, but may extend to other brainstem structures which are functionally involved in the programming of saccades. The findings confirm the value of standardized objective examination of eye movements in the detection and clarification of subclinical lesions in the central nervous system of patients with an early diagnosis of MS or ON.

Adolescent↗
PubMed1990

Neuronal activity in the lateral cerebellum of trained monkeys, related to visual stimuli or to eye movements.

1. The responses of neurones in the lateral cerebellar cortex to visual stimuli and to eye movements were recorded in rhesus monkeys trained to perform visually guided arm and eye movements in a tracking task. 2. Twenty-two of 134 units recorded (16%) modulated their discharge in response to a bright Xenon flash. They were mainly located in the dorsal paraflocculus. Among those identified as Purkinje cells both simple spike and climbing fibre responses to the flash were seen. (72% of the units were related to arm movements; these were centred in the paramedian lobule, and have been described fully in Marple-Horvat & Stein (1987).) 3. The visual responsiveness of one of the units varied according to the phase of the monkey's task. Around the time that the target stepped, which was the monkey's cue to move, its sensitivity to other stimuli disappeared. 4. Only two neurones responded to the movements of the tracking target. These responses were conditional upon the monkey using visual signals to guide his movements; they did not respond to the target step if he moved before the target did. 5. Fourteen units (10%) located in crus I and II and lobulus simplex correlated strongly with the velocity of horizontal eye movements. Only one of these also responded to visual stimuli. 6. Thus most neurones were found to carry only visual, or eye movement, or limb movement information rather than combinations of these signals; they were located in different but overlapping regions of lateral cerebellar cortex. Visually responsive neurones are probably involved in planning the visual goal of movements, while eye and arm movement neurones probably help to create co-ordinative structures for executing voluntary eye and arm movements.

Action Potentials↗
PubMed2000

Effects of prediction on timing and dynamics of vergence eye movements.

Periodic square waves were used to generate predictable vergence eye movement responses. The timing and dynamic characteristics of vergence eye movement responses to predictable and non-predictable stimuli were compared. Results showed significant changes in timing characteristics along with a highly characteristic anticipatory movement in the early part of predictable vergence responses. This phenomenon is similar to that seen in saccadic eye movements and appears to influence the timing and dynamics of the subsequent vergence response. A model-based analysis of dynamics showed that the pulse width, pulse gain, and step gain of the motor command signal did not show major differences between predictable and non-predictable response. However, other model parameters related to the acceleration of the response showed a substantial decrease when the movements were predictive.

Eye Movements↗
PubMed1987

Eye movements produced by utricular and saccular stimulation.

This study investigated the direction of eye movements produced by localized high frequency electrical stimulation of spots on the utricular and saccular macula in lightly anesthetized guinea pigs using fine bipolar stimulating electrodes to minimize current spread and attempting to keep the other labyrinthine sensory regions functional. Threshold stimulating currents produced upward or upward-torsional movements of the ipsilateral eye. There was no evidence of different directions of eye movements corresponding to different hair cell orientations, nor was there evidence of opposite directions of eye movements produced by stimulation on opposite sides of the striola. These results are not consistent with the earlier report of Fluur and Mellström (8-10) and reasons for this conflict are considered.

Animals↗
PubMed1996

[Three-dimensional analysis of vestibulo-ocular reflexes--the relation between head position and eye movement].

Three-dimensional analysis of vestibulo-ocular reflexes, using a computerized eye movement analysis system, was carried out in 16 normal human subjects. We examined the relationship between head position and vestibulo-ocular reflexes. The purpose of this study was to clarify the relationship between the functional plane and the anatomical position of the semicircular canals. The subjects were stimulated by pendular rotation with their heads fixed between 40 degrees nose down and 50 degrees nose up in 10 degrees steps with respect to the orbitomeatal line and the lateral canal line. The gain in horizontal eye movement which results from the lateral canal, was the highest at 20 degrees nose down. On the other hand, the gains in vertical and torsional eye movement, which result from the vertical canals, were the lowest at 10 degrees nose up. The phase of vertical and torsional eye movement changed 180 degrees at 10 degrees nose up. These data indicate that the functional plane of the lateral canal almost coincided with the anatomical position. However, at this functional plane of the lateral canal, the influence of vertical canals was not the least. We suggest that this could be the reason why angles formed by the intersection of the lateral canal plane and the vertical canals were not 90 degrees. We could interpret this finding as showing that at the 10 degrees nose up position, the origin of eye movement alternated between the frontal and posterior canals.

Adult↗
PubMed1994

Rapid eye movement sleep periodic leg movements in patients with spinal cord injury.

We describe three spinal cord injury cases exhibiting periodic leg movements (PLMs) in both rapid eye movement (REM) and nonrapid eye movement (NREM) sleep. The difference in the average periodicity in REM and NREM sleep was modest, but was generally shorter in REM than in NREM sleep. However, the variability associated with the PLMs was nearly three to six times smaller in REM than in NREM sleep, suggesting that the periodicity of the PLMs in REM sleep was more precise than in NREM sleep. The finding of PLMs in these patients suggests that a spinal cord injury may permit the expression of a spinal PLM generator, which may be an unusual presentation of a spinal locomotor generator. The PLM generator would be displayed when the descending inhibitory spinal pathways are interrupted by a spinal injury. The rapid periodicity of the PLM generator in REM sleep, compared with NREM sleep, may result from an increase in sympathetic activity normally accompanying this sleep state. Alternative explanations for the occurrence of PLMs in spinal injury are the influence of adverse sleeping position, age, an increase in circulating catecholamines and peripheral perfusion. We conclude that the presence of PLMs may be an important, but neglected, sleep disorder in spinal cord patients. Therefore, health care professionals should be aware of the possibility of sleep-related PLMs when these patients have sleep and/or waking complaints.

Adult↗
PubMed1980

Eye movements evoked by microstimulation of dorsal cap of inferior olive in the rabbit.

1. Microstimulation was used in an attempt to activate selectively neurons of the dorsal cap of the inferior olive in unanesthetized rabbits, and the eye movements evoked by this microstimulation were recorded. 2. Trains of microstimulation (20--50 microA, 0.1- to 0.2-ms pulses, 10--60 pulses/s, 2--8 s duration) evoked low-velocity conjugate eye movements directed toward the side of the stimulated olive. These evoked eye movements were interrupted by resetting eye movements in the opposite direction and could be evoked only if the rabbit was in darkness. 3. The velocity of the evoked eye movements increased during a stimulus train and gradually decreased after the stimulation was terminated. 4. The low-velocity eye movements appeared to combine with eye movements evoked by vestibular stimulation without any significant interaction. 5. After transection of the olivocerebellar pathway or destruction of the contralateral cerebellar flocculus, dorsal cap microstimulation no longer evoked ipsilaterally directed eye movements.

Animals↗
PubMed2004

Review of rapid eye movement behavior sleep disorders.

The spectrum of rapid eye movement behavior disorders (RBD) spans various age groups, with the greatest prevalence in elderly men. Major diagnostic features include harmful or potentially harmful sleep behaviors that disrupt sleep continuity and dream enactment during rapid eye movement sleep. In RBD patients, the polysomnogram during rapid eye movement sleep demonstrates excessive augmentation of chin electromyogram or excessive chin or limb phasic electromyogram twitching. RBD may be associated with various neurodegenerative disorders, such as multiple system atrophy, Parkinson's disease, and dementia with Lewy bodies. Other co-morbid conditions may include narcolepsy, agrypnia excitata, sleepwalking, and sleep terrors. RBD is hypothesized to be caused by primary dysfunction of the pedunculo-pontine nucleus or other key brainstem structures associated with basal ganglia pathology or, alternatively, from abnormal afferent signals in the basal ganglia leading to dysfunction in the midbrain extrapyramidal area/ pedunculo-pontine nucleus regions.

Adolescent↗
PubMed2001

Eye movements during reading: some current controversies.

For many researchers, eye-movement measures have become instrumental in revealing the moment-to-moment activity of the mind during reading. In general, there has been a great deal of consistency across studies within the eye-movement literature, and researchers have discovered and examined many variables involved in the reading process that affect the nature of readers' eye movements. Despite remarkable progress, however, there are still a number of issues to be resolved. In this article, we discuss three controversial issues: (1) the extent to which eye-movement behavior is affected by low-level oculomotor factors versus higher-level cognitive processes; (2) how much information is extracted from the right of fixation; and (3) whether readers process information from more than one word at a time.

Journal Article↗
PubMed1983

Predictive eye movements do not discriminate between dyslexic and control children.

Pavlidis has suggested that predictive saccadic tracking eye movements distinguish between reading disabled and normal children. We have examined saccadic eye movement tracking in 34 dyslexic and 33 control subjects, between 10 and 12 yr old. The subjects were equivalent in performance IQ (WISC-R), with differences between verbal and performance IQ of less than 30 points. Children with neurological, visual or auditory deficits or histories of emotional problems and hyperactivity were excluded. There were no differences between the groups on the eye movement tracking task when scored objectively by computerized analysis of the eye movement records, or by ranking of the records by an experienced observer. Our results (and those of other recent studies) fail to support Pavlidis' contention that eye movements hold the key to dyslexia.

Child↗
PubMed1983

Eye movement dysfunctions in psychiatric patients: a review.

Impairments of smooth pursuit eye movements occur in a high proportion of schizophrenic patients and in a lower but significant percentage of patients with affective psychoses, as well as patients with structural and metabolic disorders of the central nervous system. These findings have been confirmed using a wide range of tracking tasks, recording techniques, and scoring procedures, and therefore cannot be attributed to measurement artifact. The eye movement disruption in schizophrenics does not seem to result from drug treatment or simple inattention. Eye tracking pattern appears to be under genetic control and some impairments may reflect a predisposition to functional psychosis. The smooth pursuit eye movement impairment has been attributed to a central nervous system dysfunction that manifests itself in a disorder of nonvoluntary attention. The study of other oculomotor functions, such as the oculocephalic reflex, optokinetic and vestibular nystagmus, and saccadic eye movements, suggests that the locus of the central nervous system disruption is above the brainstem.

Adult↗
PubMed1994

The relationship of anticipatory smooth eye movement to smooth pursuit initiation.

We measured anticipatory smooth eye movements and smooth pursuit initiation with predictable and unpredictable step-ramp stimuli in normal subjects. Subjects generated anticipatory eye motion before targets moved and during intervals when targets suddenly disappeared. Expectations of target trajectory modified pursuit acceleration and latency, demonstrating that pursuit initiation is not governed by visual inputs alone. Anticipatory smooth eye movements and predictive contributions to smooth pursuit had similar accelerations and velocities. Anticipation and pursuit initiation varied in parallel between subjects; anticipation was stronger in subjects who generated faster smooth pursuit. These findings imply that anticipatory and smooth pursuit eye movements are governed by a common mechanism.

Adult↗
PubMed1998

Eye movements in reading and information processing: 20 years of research.

Recent studies of eye movements in reading and other information processing tasks, such as music reading, typing, visual search, and scene perception, are reviewed. The major emphasis of the review is on reading as a specific example of cognitive processing. Basic topics discussed with respect to reading are (a) the characteristics of eye movements, (b) the perceptual span, (c) integration of information across saccades, (d) eye movement control, and (e) individual differences (including dyslexia). Similar topics are discussed with respect to the other tasks examined. The basic theme of the review is that eye movement data reflect moment-to-moment cognitive processes in the various tasks examined. Theoretical and practical considerations concerning the use of eye movement data are also discussed.

Cognition↗
PubMed1966

Sleep: suppression of rapid eye movement phase in the cat after electroconvulsive shock.

Electroconvulsive shock, administered for 5 to 7 days, reduced the daily rapid eye movement sleep time of seven cats to as little as 28 percent of base line levels. After day 4, eye movements during periods of cortical activation without tonic electromyographic activity were greatlyreduced. Although partially deprived of rapid eye movements for as long as 7 days, the cats showed no compensatory rise in rapid eye movement time during the recovery period, but controls equally deprived gave significant rebounds. Rapid eye movement time of anesthetized cats was not affected by current that usually produces con vulsions; it was lowered in animals convulsed with metrazol, but the same dosage of this drug, administered so as to avoid convulsions, had little eflect. It appears that some aspect of the convulsion is responsible for lowering the rapid eye movement time.

Animals↗
PubMed2005

Suppression of optokinesis during smooth pursuit eye movements revisited: the role of extra-retinal information.

When our eyes track objects that are moving in a richly structured environment, the retinal image of the stationary visual scene inevitably moves over the retina in a direction opposite to the eye movement. Such self-motion-induced global retinal slip usually provides an ideal stimulus for the optokinetic reflex. This reflex operates to compensate for global image flow. However, during smooth pursuit eye movements it must be shut down so that the reflex does not counteract the voluntary pursuit of moving targets. Here, we asked if retinal information is sufficient for this cancellation of the optokinetic reflex during smooth pursuit eye movements. In a series of experiments, we show that neither the eye movement-induced retinal image motion per se nor the relative motion between the pursuit target and the background are sufficient for suppression of optokinesis. We, therefore, conclude that extra-retinal information about smooth pursuit eye movements is required for the cancellation of the optokinetic reflex.

Blinking↗