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PubMed1984

Projections from the superior colliculus to a region of the central mesencephalic reticular formation (cMRF) associated with horizontal saccadic eye movements.

Radioactive wheatgerm agglutinin (WGA) and horseradish peroxidase (HRP) were injected into portions of the mesencephalic reticular formation at sites where electrical stimulation induced either small or large contralateral horizontal saccadic eye movements. We have designated this region as the Central MRF (cMRF). It contains both cells and fiber tracts, including the efferent output of the superior colliculus (SC), destined for the dorsal tegmental decussation and the predorsal bundle. Cells labelled by WGA and HRP injections were found in the intermediate and deep layers of the superior colliculus and the adjacent central gray matter on the ipsilateral side. Injections into the dorsal cMRF, at sites where small saccades were induced, caused labelling of cells in the rostral intermediate layer of SC. Injections into the ventral cMRF, at points where large saccades were elicited, caused labelling of cells in the caudal intermediate layer of SC. The deepest layers of SC and the adjacent central gray were also labelled from the small eye movement region of dorsal cMRF. We interpret these findings to indicate that the intermediate layers of SC send axonal projections to the horizontal eye movement region of the MRF in a topographic fashion. The projection from the intermediate layer is organized so that regions in SC and cMRF related to small or to large eye movements are interconnected. The results support the hypothesis that cMRF is a topographically organized area, involved, like SC, in the control of eye movements. Since both cMRF and the superior colliculus project to areas of the pons and medulla where saccadic eye movements are produced, they could give rise to parallel pathways for the generation of contralateral saccades.

Animals↗

PubMed2001

Fractal analysis of eye movements during reading.

We present a new method for the analysis of reading eye movements based on the methods of nonlinear dynamics. In this preliminary study, the eye movements of normal and abnormal readers were analyzed for evidence of chaotic, nonlinear dynamical behavior. Both power spectral density analysis and fractal dimension determination showed evidence of nonlinearity as manifest in chaotic behavior. The computed fractal dimension of the system's presumed attractor seemed directly related to qualitative assessment of reading ability. Representative subjects did not differ in a similar analysis of pursuit movements. Although fractal analysis did not distinguish unconditionally between normal and abnormal reading in this preliminary study, it nevertheless offers a promising hitherto unused approach to the analysis of eye movements and the modeling of oculomotor behavior.

Adult↗

PubMed1982

Eye position signals in the flocculus of the monkey during smooth-pursuit eye movements.

1. Discharges of Purkinje cells and mossy fibres were recorded from the flocculus of monkeys trained to fixate a small visual target and to track the target when it moved slowly.2. Discharges of Purkinje cells changed tonically with shifts of gaze. Firing rates were linearly related to eye positions for either the entire or more than half the eye-position range in 12.6% of Purkinje cells tested (76/603 units).3. The eye position-related activity (position component) was observable in these cells also during smooth-pursuit eye movements. It was typically seen during slow eye movements (velocities less than 10 deg/s) but became undetectable during high velocity movements (faster than 50 deg/s).4. The position component became prominent when smooth pursuit was executed at the preferred loci of the individual cells. In the majority of the cells tested at their preferred loci, the position component was observable to a relatively high frequency, such as 0.5 Hz (+/- 10 deg; peak velocity 31 deg/s).5. Forty-five mossy fibre units showed saccade-related bursts and position-related intersaccadic tonic activity during steady eye position. In each unit, the position component was found only during fixations within a specific range of eye positions. During fixations outside these regions, all position-related mossy fibres were completely silent.6. During sinusoidal smooth-pursuit eye movements, the mossy fibres also displayed cyclic modulations in activity. All fibres discharged with eye movements in one direction and were silent during eye movements in the other direction.7. Saccade-related bursts from mossy fibres led the onset of saccades, ranging from 0 to 19 ms with a mean lead-time of 6.9 ms. This observation negates the possibility that the position-related signals might represent proprioceptive impulses from the stretch receptors of the extraocular muscle.

Action Potentials↗

PubMed1993

Eye movement disorders.

The past year's literature on eye movements is characterized by two trends: first by the examination of eye movement organization in the three planes of eye rotation in normal subjects (there is yet no publication about abnormalities of this three-dimensional organization in patients) and second by the increasing awareness of clinicians that the characteristics of saccades are highly task-dependent, and that the saccadic performance of patients must be tested under various conditions. Several papers try to establish a correlation between the site of a lesion and abnormalities of specific parameters of task-dependent saccades. For a better understanding, the different experimental tasks for the elicitation of saccades are explained in the text.

Brain Damage, Chronic↗

PubMed1993

Effect of rapid eye movement sleep deprivation on rat brain monoamine oxidases.

Monoamine oxidase, monoamine oxidase-A, and monoamine oxidase-B activities were compared in free moving, rapid eye movement sleep-deprived, recovered, and control rat brains. The activities were estimated in the whole brain, cerebrum, cerebellum, whole brainstem, medulla, pons, and midbrain. The flowerpot method was used for continuing deprivation for one, two, or four days. Monoamine oxidase activity decreased significantly in the cerebrum and the cerebellum of the sleep-deprived rats, whereas monoamine oxidase-A and monoamine oxidase-B were differentially affected. Medullary MAO-A was the first to be affected, showing an increase after just one day of rapid eye movement sleep deprivation, while longer deprivation decreased its activity. The activity of monoamine oxidase-B was not significantly affected in any brain areas of the deprived rats until after two days of rapid eye movement sleep deprivation. All the altered enzyme activities returned to control levels after recovery. Control experiments suggest that the decrease was primarily caused by the rapid eye movement sleep deprivation and was not due to nonspecific effects. These findings are consistent with past studies and may help to explain earlier observations. The results support the involvement of aminergic mechanisms in rapid eye movement sleep. The plausible reasons for the changes in the activities of monoamine oxidases, after rapid eye movement sleep deprivation, are discussed.

Animals↗

PubMed1994

Eye movement abnormalities in carriers of blue-cone monochromatism.

PURPOSE: Although impaired color vision and ERG changes have been detected in carriers of blue-cone monochromatism (BCM), no eye movement abnormalities have been identified. Quantitative eye movements of three obligate carriers of BCM were analyzed. METHODS: Horizontal and vertical eye movements of three obligate carriers of two families with BCM with visual acuity of 20/20 or better were recorded using the magnetic search coil technique. Subjects were examined fixing in primary and eccentric gaze and during horizontal and vertical smooth pursuit at 20 degrees, 40 degrees, and 80 degrees per second. RESULTS: All carriers displayed fixation instability. In two subjects, fine-amplitude upbeat, jerk-type nystagmus was detected. Reduced pursuit gain was found in the carriers. The third subject had small downbeat nystagmus. CONCLUSION: Abnormal eye movements are described for the first time in carriers of BCM. The nystagmus is clearly distinct from congenital or latent nystagmus and is similar to the nystagmus reported in BCM. Because all carriers had excellent visual acuity, in BCM, nystagmus is intrinsic to the disease and can appear independently of the visual defect.

Adult↗

PubMed1998

The effect of rapid eye movement (REM) sleep on upper airway mechanics in normal human subjects.

1. It has been proposed that the upper airway is more compliant during rapid eye movement (REM) sleep than during non-rapid eye movement (NREM) sleep. The purpose of this study was to test this hypothesis in a group of subjects without sleep-disordered breathing. 2. On the first night, the effect of sleep stage on the relationship of retropalatal cross-sectional area (CSA; visualized with a fibre-optic scope) to pharyngeal pressure (PPH) measured at the soft palate during eupnoeic breathing was studied. Breaths during REM sleep were divided into phasic (associated with eye movements) and tonic (not associated with eye movements). There was a significant decrease in pharyngeal CSA during NREM sleep compared with wakefulness. There was no further decrease observed during either tonic or phasic REM sleep. Pharyngeal compliance, defined as the slope of the regression CSA versus PPH, was significantly increased during NREM sleep compared with wakefulness and REM sleep, with the compliance during both tonic and phasic REM sleep being similar to that observed in wakefulness. 3. On the second night, the effect of sleep stage on pressure-flow relationships of the upper airway was investigated. There was a trend towards the upper airway resistance being highest in NREM sleep compared with wakefulness and REM sleep. 4. We conclude that the upper airway is stiffer and less compliant during REM sleep than during NREM sleep. We postulate that this difference is secondary to differences in upper airway vascular perfusion between REM and NREM sleep.

Airway Resistance↗

PubMed1983

Rate of entrance of benzodiazepines into the brain determined by eye movement recording.

1 Peak saccadic velocity of horizontal eye movements, saccade duration at 30 degrees of amplitude and saccade reaction time were measured in six drug free male subjects. 2 In two separate experiments, intravenous doses of diazepam (5 mg), lorazepam (2 mg), chlordiazepoxide (25 mg) and placebo were given, and eye movement recordings were made before and at frequent intervals after drug administration. 3 All the benzodiazepines produced a significant impairment of peak saccadic velocity and saccade duration. Only lorazepam significantly affected saccade reaction time. 4 Time to achieve maximum effect was 10 min after diazepam, 29 min after lorazepam and 42 min after chlordiazepoxide.

Adult↗

PubMed1991

Selective impairment of smooth-pursuit eye movements due to an ischemic lesion of the basal pons.

Voluntary and reflex-like eye movements were measured in a patient with an ischemic lesion of the right basal pons. Ipsilateral smooth-pursuit eye movements were predominantly impaired and interrupted by saccades. This profound smooth-pursuit deficit contrasted with only minor abnormalities of visually guided saccades and the vestibulo-ocular reflex. A selective disturbance of smooth-pursuit eye movements due to a lesion of the basal pons in this patient concurs with recent work in monkeys suggesting that smooth-pursuit eye movements are mediated by a parietooccipito-ponto-cerebellar pathway.

Brain Ischemia↗

PubMed1988

Frequency response analysis of human saccadic eye movements: estimation of stochastic muscle forces.

A frequency response method is used to estimate parameters of a fourth-order model of the oculomotor system and the active state tensions during a saccadic eye movement. The lateral and medial rectus muscle of each eye is modeled as a parallel combination of an active state tension generator with a viscosity and elastic element, connected to a series elastic element. The eyeball is modeled as a sphere connected to a viscosity and elastic element. Each of these elements is assumed to be ideal and linear. The active state tension for each muscle is modeled by a low-pass filtered pulse-step waveform. Initial estimates of the oculomotor mechanical components are based on physiological evidence. Initial estimates of the active state tension are based on an extrapolation of the eye movement trajectory. Horizontal saccadic eye movements were recorded from infrared signals reflected from the anterior surface of the cornea and then digitized. Parameter estimates were calculated for the model by using a conjugate gradient search program which minimizes the integral of the absolute value of the squared error between the model and the data. The predictions of the model are shown to be in good agreement with the data. Final estimates of motoneuronal activity demonstrate that the agonist muscle is maximally stimulated during the early portion of a saccadic eye movement regardless of the amplitude of the saccade; only the duration of the maximal stimulation affects the size of the saccade. The antagonist muscle is completely inhibited during the period of maximum agonist muscle stimulation. Furthermore, it is demonstrated that saccade motoneuronal activity is a stochastic phenomenon.

Elasticity↗

PubMed1997

Oculopalatal myoclonus: eye movement studies, MRI findings and the difficulty of treatment.

Two cases of oculopalatal myoclonus with bilateral horizontal gaze palsies are presented. The abnormal vertical eye movements developed several months after brain stem haemorrhage. Eye movement measurements showed rhythmical vertical eye movements at similar rates (2.3 Hz and 2.4 Hz), unaffected by attempts to fixate, converge or gaze in any direction. T2-weighted MRI scans showed bilateral enlargement of the inferior olivary nuclei in both cases, which confirms the expected pathology previously demonstrated on autopsy. Both patients had severe oscillopsia and an attempt was made to improve this by bilateral disinsertion of the vertical rectus muscles. The pendular eye movements continued but were greatly reduced, in one case enough to relieve the oscillopsia. However, after 6 months retrobulbar botulinum toxin was required to continue to provide relief from the oscillopsia. Other treatment options, including pharmacological agents, are discussed.

Aged↗

PubMed2004

Adaptive changes in vergence eye movements induced by vergence-vestibular interaction training in monkeys.

Clear vision of objects moving in three-dimensional space near an observer is attained by a combination of smooth-pursuit and vergence eye movements. The two systems must interact with the vestibular system to maintain the image of the object on the fovea. Previous studies showed that training with smooth-pursuit vestibular interactions resulted in adaptive changes in the smooth-pursuit response. Although vergence and smooth-pursuit systems are thought to have separate neural substrates, recent studies indicate that the caudal parts of the frontal eye fields that receive vestibular inputs contain neurons that discharge in response to combinations of smooth-pursuit and vergence. This combination of discharge sensitivities suggests the possibility that adaptive changes may be induced in the vergence system by vestibular inputs during vergence-pursuit training. To explore this possibility, we examined the effects of training with conflicting vestibular and vergence tracking in four head-stabilized monkeys. Animals were rewarded for tracking a laser spot that moved towards or away from them at 1 Hz in phase with sinusoidal whole-body rotation (+/- 5 degrees) in the pitch plane; the spot moved closer when the monkey's nose moved downward. From the monkey's point of view, the spot moved sinusoidally 10-66 cm in front of them along the mid-sagittal plane, requiring symmetrical vergence eye movements of 4.8 degrees for each eye. Eye movements induced by equivalent spot motion at 0.3-1.0 Hz with or without chair rotation were examined before and after training for each session (0.5-1.0 h). Before training, pitch rotation alone in complete darkness did not induce vergence eye movements in any of the monkeys tested. Vergence tracking without chair rotation showed decreased gain and increased phase lag (re vergence target velocity) at frequencies above 0.5 Hz. After training, the vergence response during chair rotation with the spot showed significantly higher gains and smaller phase lags at 0.3-1.0 Hz in all monkeys. Pitch rotation alone in complete darkness induced vergence eye movements with gains (eye vergence/chair) of 0.15-0.35 after training in two monkeys. These results suggest that vestibular information can be used effectively to modify vergence tracking.

Adaptation, Physiological↗

PubMed1982

Lateral eye-movements, field dependence and denial.

Conjugate lateral eye-movements can be used to classify some people into two distinct groups (left-movers and right-movers), who differ on various cognitive and personality variables reflecting stylistic reliance on the cognitive mode of a single hemisphere. In this study left-movers relied more heavily on denial as a defense. Field dependence tended to be related to both denial and left eye-movements by males but not females. The results are discussed in terms of a possible neuropsychological substrate for denial.

Adolescent↗

PubMed2004

Eye movements in neurodevelopmental disorders.

PURPOSE OF REVIEW: The aim of this paper is to review the literature on eye-movement abnormalities associated with neurodevelopmental disorders. Eye-movement testing is a non-invasive quantitative approach for evaluating brain systems across the age spectrum. It thus provides a promising methodology for characterizing and documenting maturational abnormalities in brain systems associated with neurodevelopmental disorders. RECENT FINDINGS: Recent oculomotor studies have made significant contributions to the understanding of neurodevelopmental disorders, most notably in autism, attention-deficit/hyperactivity disorder, and Tourette's syndrome. Notably different patterns of deficits have been found in these disorders and have helped to clarify their pathophysiology. SUMMARY: Eye-movement studies have begun to serve as a useful approach for studying cognitive and neurophysiological aspects of neurodevelopmental disorders. They also have potential as a strategy for establishing quantitative endophenotypes for genetic research, and for monitoring beneficial and adverse effects of pharmacotherapies. Studies are needed that involve larger patient populations, longitudinal characterization of developmental failures, patients free from central nervous system-active medications, and that use functional imaging, as patients perform eye-movement tasks, for direct identification of clinically relevant abnormalities in brain systems.

Attention Deficit Disorder with Hyperactivity↗

PubMed1990

19th century mechanical models of eye movements, Donders' law, Listing's law and Helmholtz' direction circles.

Donders, Ruete, von Graefe, von Helmholtz, Listing, Volkmann and many others have provided the broad outline of an answer to the question how the eye rotates during eye movements. Many mechanical models of eye movements, ophthalmotropes, have been constructed and studied in the nineteenth century. These models have primarily served to explain Donders' and Listing's Laws on the nature of eye movements. As both Donders' Law and Listing's Law are easier to understand when seen against the background of the coordinate systems used to describe eye movements, all of the coordinate systems currently in use in the diagnosis and treatment of strabismus are described. In addition, the reader is introduced to a coordinate system based on von Helmholtz' direction circles, circles describing the direction of the horizontal and vertical retinal meridians in all positions of gaze.

Eye Movements↗

PubMed1995

Supranuclear eye movement dysfunction in mitochondrial myopathy with tRNA(LEU) mutation.

A patient with multiple neurological deficits and biopsy-proven mitochondrial myopathy with mutation of tRNA(LEU) at nucleotide 3243 was referred for eye movement evaluation. He had restricted range of voluntary motions in all directions and full range of eye movements on passive rotation of head while fixating a visual target. Eye movement recordings revealed decreased horizontal and vertical saccadic velocities and markedly decreased smooth pursuit gain in both directions. The vestibulo-ocular reflex showed gain abnormalities with many saccadic intrusions on the smooth reflex response. His brother, with similar mutation, was clinically asymptomatic. However, his eye movement recordings revealed slow horizontal saccadic velocities leftward and normal saccadic velocities rightward in both eyes as well as in upward and downward direction. Smooth pursuit and vestibulo-ocular reflexes were within normal limits. Although eye movement abnormalities are seen commonly in mitochondrial myopathies, the exact mechanism is not known. Our cases suggest supranuclear dysfunction as one of the mechanisms for ophthalmoparesis.

Biopsy↗

PubMed1985

Active and passive smooth eye movements: effects of stimulus size and location.

We measured active smooth pursuit eye movements and passive smooth eye movements in the open-loop condition as subjects viewed moving stimuli of different sizes and at various retinal loci. Active movements have high gain and relatively large phase lag. Passive movements have lower gain and smaller phase lag, and occur with either foveal or eccentric stimuli. They appear to be similar or identical to optokinetic movements. Although different, active and passive movements show a similar increase in amplitude and phase lag as the size of the stimulus was increased. From these findings we suggest that: (1) The stimuli for the active movements are target position and velocity; (2) the stimulus for passive movements is target velocity; and (3) the active response to target velocity is related, in part, to the passive response and thus is related to optokinesis.

Adult↗

PubMed1996

Saccadic and smooth pursuit eye movements in memory-impaired elderly people.

The aim of the study was to compare eye movements recorded in 14 non-demented memory impaired elderly subjects with those of 36 sex- and education-matched controls. Eye movements were recorded with the bitemporal electrooculographic technique, and analyzed with a personal computer. Saccades were elicited in accordance with reflexive, predictive and antisaccade paradigms. Smooth pursuit eye movements were elicited with a triangular ramp paradigm. The memory-impaired subjects showed a higher prevalence of increased reflexive saccade latency and a lower smooth pursuit performance index. In addition, we detected a correlation between antisaccade and reflexive saccade latencies. Our results showed very slight differences in eye movement parameters. However, our findings are in keeping with the hypothesis of a subtle involvement of differing cortical areas in memory impaired subjects.

Aged↗