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PubMed1991

Smooth periodic eye movements can entrain perceptual alternation.

The reversal signals and eye movements of three subjects looking at a Necker cube that moved sinusoidally in the subject's field of view were recorded. The aim of the experiment was to provide evidence of possible synchronisation of perceptual alternation with smooth periodic eye movements. The occurrence of synchronisation was demonstrated for a proper choice of the eye oscillation period by both a sharp reduction in the fluctuations of the reversal time and a change in the mean value of this parameter. Such variations resulted in a close match of the mean reversal time to a multiple of the eye oscillation period. Further, inversions of the direction of eye movements elicited pattern reversals in a systematic way, characteristic for each subject. The described phenomenon, which is a typical example of nonlinear-resonant behaviour, stresses a new important aspect of the complex interaction pattern relating pursuit eye movements to visual perception.

Adult↗
PubMed1998

A signal analysis method for retinal image velocity computation of vestibular-ocular reflex eye movement investigations.

The vestibulo-ocular reflex preserves clear vision when the subject's head is moving rapidly. These eye movements are measured in order to investigate equilibrium diseases and disorders in otoneurology. The retinal image velocity is calculated to be a difference signal between the head movement velocity and the eye movement velocity. The eye movement position signal as well as the head movement position signal of the subject are concurrently measured when the subject is asked to move his head according to a stimulus and his gaze is fixated to a target. Eye movements are electro-oculographically recorded and head movements with a potentiometer. Tests performed to both patients of an equilibrium laboratory and normals exemplify that the method is applicable to indicate some otoneurological diseases.

Calibration↗
PubMed1994

Eye movement dysfunction vs. language delays in migrant children.

BACKGROUND: The Developmental Eye Movement Test (DEM) is a popular visual-verbal saccade test. An advantage of the DEM is that patients with below-average verbalization or automaticity can be distinguished from patients with eye movement coordination problems. The standardized norms for the DEM were previously determined in a sample of suburban and urban children with expected age to grade levels. We hypothesize that language difficulties common in some minority groups would be reflected by subnormal DEM automaticity but not eye movement dysfunction. METHODS: A group of children in the U.S. Department of Education's Massachusetts Migrant Summer Education Program were prospectively studied with the DEM. The sample included 84 subjects (age 7-12) from various ethnic and educational backgrounds. RESULTS: Significant difference was found for most age levels in automaticity in migrant children compared to the DEM norms (independent t tests p < 0.05 DEM vertical and horizontal). However, few differences in eye movement coordination was found (p > 0.05 DEM ratios and errors). CONCLUSIONS: The data supports the hypothesis that language barriers inherent in this population are reflected by lower automaticity, but not eye movement dysfunction, as measured by the DEM. The results are important for optometrists because they demonstrate the importance of taking language and cognitive development into account before diagnosing eye movement dysfunction in culturally different children.

Child↗
PubMed1999

Firing behavior of vestibular neurons during active and passive head movements: vestibulo-spinal and other non-eye-movement related neurons.

The firing behavior of 51 non-eye movement related central vestibular neurons that were sensitive to passive head rotation in the plane of the horizontal semicircular canal was studied in three squirrel monkeys whose heads were free to move in the horizontal plane. Unit sensitivity to active head movements during spontaneous gaze saccades was compared with sensitivity to passive head rotation. Most units (29/35 tested) were activated at monosynaptic latencies following electrical stimulation of the ipsilateral vestibular nerve. Nine were vestibulo-spinal units that were antidromically activated following electrical stimulation of the ventromedial funiculi of the spinal cord at C1. All of the units were less sensitive to active head movements than to passive whole body rotation. In the majority of cells (37/51, 73%), including all nine identified vestibulo-spinal units, the vestibular signals related to active head movements were canceled. The remaining units (n = 14, 27%) were sensitive to active head movements, but their responses were attenuated by 20-75%. Most units were nearly as sensitive to passive head-on-trunk rotation as they were to whole body rotation; this suggests that vestibular signals related to active head movements were cancelled primarily by subtraction of a head movement efference copy signal. The sensitivity of most units to passive whole body rotation was unchanged during gaze saccades. A fundamental feature of sensory processing is the ability to distinguish between self-generated and externally induced sensory events. Our observations suggest that the distinction is made at an early stage of processing in the vestibular system.

Animals↗
PubMed2002

A contingent speech technique in eye movement research on reading.

A novel eye-movement-contingent method is presented. It builds on and extends established eye-movement-contingent visual display change methods in that it uses movements of the eyes to control the presentation of acoustic information during sentence reading. In one implementation, an irrelevant spoken word is presented when the eyes cross a predetermined spatial boundary before they move on to a selected visual target word. The relationship between the spoken word and the visual target is manipulated, and the pattern of interference, caused by the presentation of the spoken word, is used to determine the nature and time course of activated representations. Results from three recently completed experiments in which the technique was used show that a word's phonological code remains active after it has been read and that the activated code has speech-like properties.

Eye Movements↗
PubMed2006

Fixational eye movements in normal and pathological vision.

Most of our visual experience is driven by the eye movements we produce while we fixate our gaze. In a sense, our visual system thus has a built-in contradiction: when we direct our gaze at an object of interest, our eyes are never still. Therefore the perception, physiology, and computational modeling of fixational eye movements is critical to our understanding of vision in general, and also to the understanding of the neural computations that work to overcome neural adaptation in normal subjects as well as in clinical patients. Moreover, because we are not aware of our fixational eye movements, they can also help us understand the underpinnings of visual awareness. Research in the field of fixational eye movements faded in importance for several decades during the late 20th century. However, new electrophysiological and psychophysical data have now rejuvenated the field. The last decade has brought significant advances to our understanding of the neuronal and perceptual effects of fixational eye movements, with crucial implications for neural coding, visual awareness, and perception in normal and pathological vision. This chapter will review the type of neural activity generated by fixational eye movements at different levels in the visual system, as well as the importance of fixational eye movements for visual perception in normal vision and in visual disease. Special attention will be given to microsaccades, the fastest and largest type of fixational eye movement.

Fixation, Ocular↗
PubMedDate not supplied

Age diminishes performance on an antisaccade eye movement task.

Tthe antisaccade eye movement task, which has been linked to frontal lobe function, presents a target in one visual field and asks subjects to move their eyes to the same location in the opposite field. The task requires inhibition of the reflexive prosaccade to the cue, initiation of the antisaccade to the opposite field, and visuo-spatial memory of the cue location. Forty-two subjects from 19-79 years of age performed this task and a control task, visually guided saccades to the cue itself, to determine which functions are affected by aging. The time to initiate antisaccades increased linearly with age at a rate greater than the time to initiate visually guided saccades. This difference suggests that the processing time to inhibit the incorrect movement to the cue is selectively increased with age. Older subjects also made more incorrect prosaccadic movements to the cue, a finding consistent with the loss of inhibitory processing capacity. The accuracy of movements did not change, which suggests that visuo-spatial memory is unaffected by aging.

Adolescent↗
PubMed2006

Eye-movement responses to disparity vergence stimuli with artificial monocular scotomas.

The effects of artificial monocular scotomas on eye-movement responses to horizontal disparity vergence stimuli were studied in six subjects with normal binocular vision. Subjects viewed stereoscopic 1.5 degrees horizontal step disparity vergence stimuli through liquid crystal shutter glasses. The central portion of the stimulus presented to the right eye was removed to simulate monocular artificial scotomas of variable diameters (2 degrees to 10 degrees ). Eye movements were recorded with a binocular head-mounted eye tracker. Responses included pure vergence, vergence followed by saccades, and pure saccadic eye movements. The rate of responses with saccadic eye movements increased with the diameter of the artificial scotoma (p < 0.0001); there was an increase in the rate of responses starting with saccades (p < 0.0001), as well as an increase in the rate of saccades after initial vergence responses (p < 0.01). The probability of saccades after initial vergence responses was affected by the open-loop gain of the vergence response (p < 0.001). The open-loop gain decreased with increased diameters of the artificial scotomas (p < 0.0001). As the diameter of the artificial scotomas increased, the amplitude of the initial vergence eye-movement responses decreased, and the prevalence of saccadic eye movements and asymmetric vergence increased. The effects of the diameter of artificial monocular scotomas on eye-movement responses in subjects with normal binocular vision are consistent with the effects of diameter of suppression scotomas on eye-movement responses to disparity vergence stimuli in patients with infantile esotropia.

Adolescent↗
PubMed2006

[Saccadic eye movements in children with reading disorders].

Several reports raised the possibility that dysfunction of saccadic eye movements produces reading disorder (RD), although opposite conclusions have also been reported. In this study, saccadic eye movements were investigated in 13 forth graders with RD and 20 age-matched controls during reading and non-reading tasks. Compared to the control group, children with RD showed significantly higher incidences of both forward and backward saccadic eye movements in reading tasks, while they revealed a significantly lower number of saccadic eye movements in response to sequentially moving targets in two types of non-reading tasks. These problems, seen in non-reading tasks, suggest that excessive saccadic eye movements observed in RD children during reading are not produced by mechanisms involved in the language and phonological processes alone, but also those in the saccadic eye movement process. Dysfunction in the saccadic eye movements could be one of the causal factors that produce RD.

Child↗
PubMed2002

Interaction between visual and vestibular signals for the control of rapid eye movements.

To investigate interactions between voluntary and reflexive eye movements, five subjects were asked to make pro- or anti-saccades to various oblique locations cued by a head-fixed flash while being rotated sinusoidally in yaw (0.17 Hz; 73 degrees /s peak velocity) in complete darkness. Eye movements were recorded with the coil technique. In the pro-saccade task, targeting responses showed clear compensation for the intervening nystagmus, but there was a marked increase in horizontal scatter. Most quick phases directed into the hemifield opposite to the flash (away trials) were suppressed from ~100 ms onward. By contrast, quick phases directed into the hemifield of the flash (toward trials) continued virtually unabated until visually triggered saccades began to appear. From 80 ms onward, these vestibularly triggered movements showed signs of metrical modification by the visual signal. In the anti-saccade experiments, suppression of quick phases away from the flash was just as strong as in the pro-saccade experiments, and error rates in these trials were almost as low as in stationary control conditions. Suppression of quick phases directed toward the flash was a new phenomenon that emerged only in anti-saccade experiments. Since this inhibition had a late onset and was only partial, error rates in anti-saccade toward trials were very high. At short latencies, both components of most rapid eye movements were wrongly directed toward the flash. This was followed by a stage with frequent incongruent responses in which unsuppressed quick phases provoked an incorrect horizontal movement, whereas the vertical component showed a correct anti-saccade response. At still longer latencies, most responses were correct in both components. The visual modification of short-latency responses in both tasks showed that rapid eye movements could not simply be classified as either voluntary or reflexive, but suggested that signals underlying each class could merge into a compromise response. That vestibular rotation during the anti-saccade task may cause a wrongly directed horizontal component resembling a quick phase, combined with a vertical component expressing a correct anti-saccade signal, reveals a remarkable independence at the component level. These observations suggest that voluntary and involuntary movements can be programmed in parallel. This behavior is explained most parsimoniously by assuming that the two signals converge at a component-coding stage of the system, rather than at a vectorial coding stage.

Adult↗
PubMed1998

Age-related performance of human subjects on saccadic eye movement tasks.

We measured saccadic eye movements in 168 normal human subjects, ranging in age from 5 to 79 years, to determine age-related changes in saccadic task performance. Subjects were instructed to look either toward (pro-saccade task) or away from (anti-saccade task) an eccentric target under different conditions of fixation. We quantified the percentage of direction errors, the time to onset of the eye movement (saccadic reaction time: SRT), and the metrics and dynamics of the movement itself (amplitude, peak velocity, duration) for subjects in different age groups. Young children (5-8 years of age) had slow SRTs, great intra-subject variance in SRT, and the most direction errors in the anti-saccade task. Young adults (20-30 years of age) typically had the fastest SRTs and lowest intra-subject variance in SRT. Elderly subjects (60-79 years of age) had slower SRTs and longer duration saccades than other subject groups. These results demonstrate very strong age-related effects in subject performance, which may reflect different stages of normal development and degeneration in the nervous system. We attribute the dramatic improvement in performance in the anti-saccade task that occurs between the ages of 5-15 years to delayed maturation of the frontal lobes.

Adolescent↗
PubMed1976

Braking saccade--a new fast eye movement.

A new type of fast eye movement (FEM) is described whose main function is to stop a runaway slow eye movement (SEM). It conforms to the velocity-amplitude relationship characteristic of other types of saccades. The identification of this FEM is the result of examination of the many waveforms manifested by subjects with congenital nystagmus. It is a common, repeatable phenomenon present in all subjects with any of six different types of nystagmus waveform. The fact that braking saccades reset SEM to zero velocity, whereas no other type of saccade interacts with SEM, indicates a developmental mechanism in such subjects.

Eye↗
PubMed1994

Fixation disengagement and eye-movement latency.

We examined eye-movement latencies to a target that appeared during visual fixation of stationary stimulus, a moving stimulus, or an extrafoveal stimulus. The stimulus at fixation was turned off either before target onset (gap condition) or after target onset (overlap condition). Consistent with previous research, saccadic latencies were shorter in gap conditions than they were in overlap conditions (the gap effect). In Experiment 1, a gap effect was observed for vergence eye movements. In Experiment 2, a gap effect was observed for saccades directed at a target that appeared during visual pursuit of a moving stimulus. In Experiment 3, a gap effect was observed for saccades directed at a target that appeared during extrafoveal fixation. The present results extend reports of the gap effect for saccadic shifts during visual fixation to (a) vergence shifts during visual fixation, (b) saccadic shifts during smooth visual pursuit, and (c) saccadic shifts during extrafoveal fixation. The present findings are discussed with respect to the incompatible goals of fixation-locking and fixation-shifting oculomotor responses.

Attention↗
PubMed1998

Eye movement abnormalities in myotonic dystrophy.

We studied saccade and smooth pursuit eye movements in 31 patients suffering from myotonic dystrophy (MD). On the basis of mean value comparisons, saccades were slower and hypometric and smooth pursuit eye movements performed worse in MD patients than in controls. On an individual basis, saccade duration was prolonged in 67.7%, saccades were hypometric in 19.4%, saccade latency was delayed in 9.7%, and the smooth pursuit performance index was decreased in 9.7% of patients. Eye movement abnormalities did not correlate with those detectable by visual, brain-stem auditory and somatosensory evoked potentials. We attempted to classify eye movement abnormalities as myogenic or neurogenic on the basis of differences in combination of eye movement abnormalities and the occurrence of D5/D35 dissociation; the latter consists of a prolonged duration for large (35 degrees) but not for small (5 degrees) saccades. Since D5/D35 dissociation occurred in 26/33 multiple sclerosis patients with increased saccade duration, we considered it to be a neurogenic pattern attributable to a central nervous system (CNS) dysfunction. A prolonged duration without dissociation especially in combination with saccade hypometria, is interpreted as a myogenic pattern, although the lack of dissociation may also occur with CNS impairment in case of a marked increase in saccade duration. Accordingly we classified the oculomotor abnormalities detected as neurogenic in 11 MD patients and as myogenic in another 10, but in some subjects belonging to the second group concomitant CNS impairment is not to be excluded.

Adolescent↗
PubMed2000

Gender differences of exploratory eye movements: a life span study.

Exploratory eye movements of normal subjects (39 male and 39 female) were recorded using an eye-mark recorder. Four parameters mean gazing time, total number of gazing points, mean scanning length, and total scanning length) were analyzed. Subjects were divided into three life spans as prepuberty (boys and girls), adult, and postpuberty. The mean gazing time of adult women was significantly longer than that of age-matched adult men, but not between men and women in prepuberty or postpuberty (postmenopausal older women and age-matched older men). The total number of gazing points of women was significantly smaller than that of men, but not significantly different between men and women in both prepuberty and postpuberty. Both the mean scanning length and total scanning length of adult women were shorter than those of age matched adult men, but no significant differences were found between men and women in both prepuberty and postpuberty. Furthermore, the mean gazing time of adult women was longer than that of men in prepuberty and postpuberty. The total scanning length of adult men was longer than that of women in both prepuberty and postpuberty. These findings suggest that gender differences of exploratory eye movements are observed only during the adult phase, which indicates that visual information processing may be regulated by gonadal hormones in humans.

Adult↗
PubMed2002

A novel role of pedunculopontine tegmental kainate receptors: a mechanism of rapid eye movement sleep generation in the rat.

Considerable evidence suggests that pedunculopontine tegmental cholinergic cells are critically involved in normal regulation of rapid eye movement sleep. The major excitatory input to the cholinergic cell compartment of the pedunculopontine tegmentum arises from glutamatergic neurons in the pontine reticular formation. Immunohistochemical studies reveal that both ionotropic and metabotropic receptors are expressed in pedunculopontine tegmental cells. This study aimed to identify the role of endogenous glutamate and its specific receptors in the pedunculopontine tegmentum in the regulation of physiological rapid eye movement sleep. To identify this physiological rapid eye movement sleep-inducing glutamate receptor(s) in the pedunculopontine tegmental cholinergic cell compartment, specific receptors were blocked differentially by local microinjection of selective glutamate receptor antagonists into the pedunculopontine tegmental cholinergic cell compartment while quantifying the effects on rapid eye movement sleep in freely moving chronically instrumented rats. By comparing the alterations in the patterns of rapid eye movement sleep following injections of control vehicle and selective glutamate receptor antagonists, contributions made by each receptor subtype in rapid eye movement sleep were evaluated. The results demonstrate that when kainate receptors were blocked by local microinjection of a kainate receptor selective antagonist, spontaneous rapid eye movement sleep was completely absent for the first 2 h, and for the next 2 h the total percentage of rapid eye movement sleep was significantly less compared to the control values. In contrast, when N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid, groups I, II, and III metabotropic receptors were blocked, total percentages of rapid eye movement sleep did not change compared to the control values. These findings suggest, for the first time, that the activation of kainate receptors within the cholinergic cell compartment of the pedunculopontine tegmentum is a critical step for the regulation of normal rapid eye movement sleep in the freely moving rat. The results also suggest that the different types of glutamate receptors within a small part of the brainstem may be involved in different types of physiological functions.

Acetylcholine↗
PubMed2005

Brain potentials before and after rapid eye movements: an electrophysiological approach to dreaming in REM sleep.

STUDY OBJECTIVE: This study examined hypotheses regarding dreaming in rapid eye movement (REM) sleep by comparing brain potentials related to rapid eye movements in REM sleep with those in wakefulness. DESIGN: Within participants. SETTING: Data were collected in a sleep laboratory. PARTICIPANTS: Fifteen healthy university students who reported having dreams frequently. MEASUREMENTS AND RESULTS: Rapid eye movements in REM sleep were recorded during natural nocturnal sleep. Saccades in wakefulness were recorded during a self-paced visual search task. The presaccadic negativity before and the lambda response after eye movements were examined. It was assumed that the presaccadic negativity reflects voluntary readiness activity before eye movements, and the lambda response reflects visual information processing after saccades in wakefulness. Brain potentials were averaged, time-locked to the onset and offset of eye movements for the presaccadic negativity and the lambda response, respectively. In wakefulness, the presaccadic negativity occurred at the centroparietal site. However, no presaccadic negativity was found during REM sleep. Lambda-like responses (P1r, P2r) were observed in REM sleep over the parietooccipital site, as were the lambda responses (P1, P2) in wakefulness. CONCLUSIONS: The finding that rapid eye movements are initiated without preparation but elicit some neural activity in the cortical visual area suggests that rapid eye movements may trigger dream images.

Adult↗
PubMed2002

Relationship between head orientation and torsional eye movements in goldfish during linear acceleration.

We analyzed torsional eye movements of normal goldfish during sinusoidal linear acceleration, altering the orientation of the fish on the linear accelerator in the yaw plane over a range of 90 degrees and in the pitch plane up to 30 degrees. We video-recorded changes of torsional eye movements associated with a body rotation in the yaw and pitch plane and analyzed them frame by frame. In normal fish, we observed clear torsional eye movements for stimuli of 0.1 G linear accelerations along the body axis in the horizontal position. Torsion occurred in the opposite direction of resultant force produced by linear acceleration and gravity. Though the amplitude of these compensatory responses increased with increasing magnitude of acceleration up to 0.5 G, the torsion angle did not fully compensate the angle calculated from gravity and linear acceleration. Furthermore, the torsion angle decreased as the longitudinal body axis deviated from the direction of linear acceleration. For the body axis perpendicular to the direction of acceleration, torsional eye movement was still observed. When we tilted the fish in the pitch plane, compensatory eye torsion occurred. The response amplitude to acceleration decreased for both head-up and head-down up to 30 degrees. These results suggested the existence of specific connections between the otolith organ and ocular muscles.

Acceleration↗