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PubMedDate not supplied

[Smooth pursuit eye movements evoked by head-phone acoustic stimulation].

Smooth pursuit eye movement evoked by binaural acoustic stimulation is examined in the present work. The effect of lateralization was achieved by modulating the interaural difference in intensity, within the headphone, following a pendular pattern. The test was performed on 10 healthy subjects; oscillation frequencies of the acoustic target being 0.15, 0.5 and 0.83 Hz, stimulus intensity 65 and 92 dB SPL. The acoustic signal consisted of white noise. Each trial was performed with eyes closed and then with eyes open. The results demonstrate that sinusoidal eye movement can only be obtained in a few subjects when the acoustic target has the lowest velocity and especially at the higher intensity. In all other cases eye movement was characterized by multiple saccades. The variability in eye movement amplitude is reduced and the value of this parameter decreases significantly under open-eye conditions. The data obtained are in agreement with other reports obtained with free field acoustic stimulation and demonstrate that smooth pursuit eye movement is principally an ocular reflex. In conclusion, acoustic smooth pursuit eye movement appears normally to be characterized by multiple saccades whose pattern can be modulated by intensity and oscillation frequency of the acoustic target as well as by the presence of visual inputs and attentional factors.

Acoustic Stimulation↗
PubMed2000

The effect of experience on the detection of small eye movements.

PURPOSE: The purpose of this study was to determine whether experience improves detection of small eye movements similar to those seen in the cover test during ideal conditions. METHODS: Three groups of examiners with varying amounts of experience in eye movement detection tasks were studied. Eight examiners were 1st-year optometry students, six were 4th-year optometry students, and six were practicing optometrists. To determine thresholds for eye movement detection, examiners indicated the horizontal direction in which the eyes of one of the experimenters moved. The direction and extent of each eye movement was randomly selected. The extent of the eye movement was one of eight logarithmic steps from a maximum that was determined through an initial session where the approximate sensitivity of the examiners was found (generally +/- 1.75 prism diopters). RESULTS: Detection thresholds were determined by fitting the data with a cumulative Gaussian function. The mean horizontal eye movement eye movement necessary to obtain 99% correct judgments was 2.65 prism diopters for the 1st-year students, 2.47 prism diopters for the 4th-year students, and 2.40 prism diopters for the practicing optometrists. CONCLUSIONS: The results indicate that during ideal conditions, little or no training is required for efficient detection of small eye movements.

Adult↗
PubMed1976

A new technique for long-term recording of eye movements in infants.

A device for recording eye movements from infants over long time periods is described. The device consists of an infrared light-emitting diode and a phototransistor mounted in a small package which covers one eye. The eyepiece is insensitive to EEG, EKG, or EMG potentials, and avoids irritation of the infant's skin from application of electrode paste. Detection of eye movements compares favorably to conventional eye movement electrodes.

Electronics, Medical↗
PubMed1996

Anticipatory smooth eye movements and predictive pursuit after unilateral lesions in human brain.

Anticipatory smooth eye movements precede expected changes in target motion. It has been questioned whether anticipatory smooth eye movements are a component of the smooth pursuit system. Five subjects with unilateral brain lesions and five control subjects were tested with predictable double-ramp stimuli to determine whether these lesions have a similar effect on horizontal, visually guided smooth pursuit, anticipatory smooth eye movements, and the predictive component of smooth pursuit. All four subjects with a brain lesion involving the parietal or parietal-frontal lobe had parallel velocity asymmetries in all three forms of smooth eye movements, with lowest velocities toward the side of the lesion. A similar uniformity and magnitude of smooth eye movement directional asymmetries were not found in control subjects. Unidirectional attenuation of these three forms of smooth eye movements provides evidence that they are part of a unified smooth eye movement system.

Brain↗
PubMed1985

Lateral eye-movement responses to visual stimuli.

The association of left lateral eye-movement with emotionality or arousal of affect and of right lateral eye-movement with cognitive/interpretive operations and functions was investigated. Participants were junior and senior students enrolled in an undergraduate course in developmental psychology. There were 37 women and 13 men, ranging from 19 to 45 yr. of age. Using videotaped lateral eye-movements of 50 participants' responses to 15 visually presented stimuli (precategorized as neutral, emotional, or intellectual), content and statistical analyses supported the association between left lateral eye-movement and emotional arousal and between right lateral eye-movement and cognitive functions. Precategorized visual stimuli included items such as a ball (neutral), gun (emotional), and calculator (intellectual). The findings are congruent with existing lateral eye-movement literature and also are additive by using visual stimuli that do not require the explicit response or implicit processing of verbal questioning.

Adult↗
PubMed2001

Multi-position eye movement detection system.

A device that records saccadic eye movements in any X-Y position is presented in this paper. Eye movements are recorded using infrared optoelectronics mounted on hemispherical shaped eyepieces, which in turn are mounted on goggles styled after an ophthalmologist's test frames. A computer controlled, wall mounted light bank facilitates targeting for eye movements. Output from the device is sent to a PC type computer and stored in the hard disk using a data acquisition board. The user interface is Windows based and the output from the goggles are represented as a trace map of plotted points. This output can also be saved or printed for future analysis and reference. The device is designed with reference to standard ISO design methodology, and subject safety and final product usage have been reviewed following ISO analysis procedures. Accuracy in tracking of eye movements is maintained by utilizing a twenty-four channel detection system, hemispherically mounted and lensed optoelectronics to reduce cross-talk due to incident light, and signal processing that attenuates incident light as well as ambient light. Also, a reset feature is included to maintain equal baseline control. An automatic switching device is included in the test frame to allow the device to "warm up," assuring that equal IR power is delivered for each subject tested. The IR units in the goggles are also modular in case replacement is required.

Equipment Design↗
PubMedDate not supplied

Dynamic asymmetries in convergence eye movements under natural viewing conditions.

PURPOSE: To clarify differences in the dynamics of convergence eye movements in response to symmetrical stimuli between the dominant eye and the nondominant eye under natural viewing conditions. METHODS: This study was conducted in 11 normal volunteers (age range, 22-30 years). The subject was seated on a chair, and the head was fixed using a bite-block. The dominant eye was determined with the "hole-in-the-card" test. Horizontal positions of the eyes were recorded using an infrared reflection device. Recordings of right eye movements were subtracted from left eye movements to obtain the vergence response. The fixation target was moved toward the center of both eyes from 50 to 20 cm in front of the face at a constant velocity in five steps (20, 30, 40, 50, and 60 cm/s). The target was moved by a pulse motor controlled by a microcomputer. The dynamic properties of each eye movement and the vergence components were analyzed. RESULTS: At velocities < or =40 cm/s, convergence responses consisted of two components: the fusion-initiating component and the fusion-sustaining component. The fusion-initiating component drove the initial faster dynamic portion of the response, and the fusion-sustaining component maintained the latter slower dynamic portion of the response. The mean peak velocity of the fusion-initiating component was significantly greater in the dominant eye than in the nondominant eye. The mean peak latency of the catch-up component was significantly shorter in the dominant eye than in the nondominant eye. CONCLUSIONS: The present study indicated that the trajectory of convergence eye movement under natural viewing conditions consists of two components, the fusion-initiating component and the fusion-sustaining component, and that the convergence response to symmetric stimuli was asymmetric between the dominant eye and the nondominant eye during the fusion-initiating phase. The neural control system of convergence eye movements preferentially drives the dominant eye during the fusion-initiating phase of the response.

Accommodation, Ocular↗
PubMed1987

The role of eye movements in motion detection.

The roles of small eye movements of fixation, and of different kinds of background in motion detection were studied. Minimum detectable displacement for a luminous line oscillating either in a blank field or in the presence of three types of background was measured under two viewing conditions: normal, when eye movements generate normal movements of the image on the retina, and stabilized when these retinal image movements were nearly eliminated. It was demonstrated that eye movements enhance motion detection for a sinusoidally moving target when the target is superimposed on a patterned background; they are detrimental when there is no background. In addition, it was found that the function relating threshold amplitude to frequency of movement is band-pass when the image is stabilized or when the bar moves on a blank field, and is more low-pass when both the background and the test target are subject to the effects of eye movements.

Eye Movements↗
PubMed1997

False perception of motion in a patient who cannot compensate for eye movements.

We are usually unaware of the motion of an image across our retina that results from our own movement. For instance, during slow-tracking eye movements we do not mistake the shift of the image projected onto the retina for motion of the world around us, but instead perceive a stable world. Following early suggestions by von Helmholtz, it is commonly believed that this spatial stability is achieved by subtracting the retinal motion signal from an internal reference signal, such as a copy of the movement command (efference copy). Object motion is perceived only if the two differ. Although this concept is widely accepted, its anatomical underpinning remains unknown. Here we describe the case of a patient with bilateral extrastriate cortex lesions, suffering from false perception of motion due to an inability to take eye movements into account when faced with self-induced retinal image slip. This is indicated by the fact that during smooth-pursuit eye movements, he perceives motion of the stationary world at a velocity that corresponds to the velocity of his eye movement; that is, he perceives the raw retinal image slip uncorrected for his own eye movements. We suspect that this deficiency reflects damage of a distinct parieto-occipital region that disentangles self-induced and externally induced visual motion by comparing retinal signals with a reference signal encoding eye movements and possibly ego-motion in general.

Adult↗
PubMed1998

The effect of oral ethanol consumption on eye movements in healthy volunteers.

Horizontal and vertical eye movements were recorded and analysed with an infrared photoelectric technique in 12 healthy volunteers under various blood alcohol concentrations (0.0, 0.5, 1.0 g/kg body weight, [% per thousand]). The predictive smooth-pursuit tracking and saccadic eye movements were studied in response to unpredictable target jumps and during scanning of a classical kitchen scene and a traffic scene. Smooth-pursuit eye movement gain value decreased dose-dependently and was compensated by an increased number of catch-up saccades. With increasing blood alcohol concentrations peak velocities of horizontal and vertical visually guided reflexive saccades decreased while their latencies to the target increased. At blood alcohol concentrations of 0.5% per thousand and 1.0% per thousand healthy volunteers showed significantly longer mean fixation durations and a lower total number of exploratory saccades when scanning both the classical kitchen scene and the traffic scene. Surprisingly, in both of these scanning tasks the total fixation duration or the relative number of exploratory saccades increased in those scene sectors in which exciting situations were presented. Additionally, the time interval needed to foveate these exciting areas for the first time increased, probably due to an attention deficit. In conclusion, these findings indicate that alcohol consumption impairs the velocity and initiation of saccadic and smooth-pursuit eye movements, but that subjects can nevertheless still recognize exciting and relevant areas of visual scenes. The significant increase in fixation time, however, does not allow scanning of the entire visual scene during an adequate period of time. Therefore the reduced visual exploration caused by alcohol reflects an impaired sensorimotor processing of active visual perception.

Administration, Oral↗
PubMed2003

Eye-movements and ongoing task processing.

This study tests the relation between eye-movements and thought processing. Subjects were given specific modality tasks (visual, gustatory, kinesthetic) and assessed on whether they responded with distinct eye-movements. Some subjects' eye-movements reflected ongoing thought processing. Instead of a universal pattern, as suggested by the neurolinguistic programming hypothesis, this study yielded subject-specific idiosyncratic eye-movements across all modalities. Included is a discussion of the neurolinguistic programming hypothesis regarding eye-movements and its implications for the eye-movement desensitization and reprocessing theory.

Choice Behavior↗
PubMed1988

Eye movements induced by linear acceleration on a parallel swing.

1. Horizontal and vertical eye movements were induced in normal human subjects by sinusoidal linear acceleration on a parallel swing. The swing frequency was 0.3 Hz and the peak horizontal and vertical acceleration ranged from 0.17 to 0.48 and 0.03 to 0.34 g, respectively. Eye movements were recorded with the scleral search coil technique. 2. With the subjects seated in the dark to stimulate the otolith-ocular reflex, swing displacement along the interaural axis induced horizontal eye movements with a mean sensitivity to translation (ST) (peak eye velocity/peak swing velocity) of 3.8 to 4.7 degrees/m and a mean phase shift (eye velocity re swing velocity) of -152 to -160 degrees. Vertical eye movements had ST and phase values comparable to those of the horizontal eye movements. When the subjects sat facing forward so that the horizontal linear accelerations occurred in the occipitonasal axis, almost identical vertical but no consistent horizontal eye movements were induced. In each case the horizontal and vertical eye movements were proportional to the horizontal and vertical displacement of the swing. 3. With the subject seated in the light looking to an earth-fixed target (synergistic visual-vestibular interaction), the gain (peak eye velocity/peak target velocity) of induced eye movements was near 1, and the phase was compensatory (i.e., approximately -180 degrees) for all stimuli (even at target velocities at which the pursuit gain was less than 1). Subjects were able to suppress the otolith-ocular responses by fixating on a target attached to the swing. The ST decreased by an order of magnitude compared with measurements in the dark without a fixation target. 4. Subjects were able to augment the ST (horizontal and vertical) by imagining an earth-fixed target. Halving the distance of the imagined target approximately doubled the ST. 5. In two of three subjects tested, the ST measured with mental alerting in the dark adaptively increased (approximately doubled) after 20 min of continuous synergistic visual-vestibular interaction. The subject who did not show an adaptive increase in ST began with the highest value of the 10 normal subjects. 6. We conclude that during linear accelerations of the head the otolith signal is correctly interpreted as head movement and not rotation of the gravity vector. The otolith-ocular reflex interacts with the visual pursuit system to improve ocular stability during translational head movements.

Adult↗
PubMed1989

Motion perception prominence alters anticipatory slow eye movements.

Perceived motion may be a stimulus for anticipatory slow eye movements. To test this possibility, the production of anticipatory slow eye movements in humans was studied using apparent motion stimuli. Short range apparent motion was produced with random dot stimuli and the anticipatory slow eye movements were isolated from the smooth pursuit responses by occasionally including trials in which the random dot stimulus did not appear. Long range apparent motion was produced with subjective contour stimuli. Both short range and long range apparent motion were found to be effective stimuli for anticipatory slow eye movements. The prominence of perceived motion was altered by changing the spatiotemporal displacement intervals in the short range apparent motion stimuli. Changing the subjective contours also changed the motion percepts of the long range apparent motion stimuli. With both stimuli, the peak anticipatory slow eye velocities that were achieved decreased as the prominence of the motion percepts decreased, while the time-course of the anticipatory responses were similar under the different conditions. These findings indicate that the expectation of perceived motion is necessary for anticipatory slow eye movements.

Adult↗
PubMed1984

[Eye movements induced by the parallel-swing method in rabbits].

Eye movements induced by sinusoidal linear accelerations generated by the parallel-sled, have been recorded by means of monocular electronystagmographic recordings in the horizontal and vertical plane. Qualitatively the recorded eye movements are vertical sinusoidal eye movements. When the sled moves to the right, the right eye moves upward, and the left eye downward. When the sled moves to the left, the inverse takes place. This seems to suggerate that the vestibulo-ocular reflex tested here, tries to compensate an imaginary rotation of the laboratory animal in the direction of the resultant acceleration stimulus. The false difference between the two eyes is 180 degrees, independant of the frequency of the sled. The false-difference between the sled and the eye movements increases with the frequency. The natural frequency is 0,6 Hz. The maximal amplitude is reached at the same frequency of 0,6 Hz (resonance frequency). Artefacts are present from the frequency of 0,8 Hz on. These are caused by movements of the needle electrodes on their own, due to the big accelerations on these frequencies. They are clearly distinguishable from the real eye movements. The gain "G" is incomplete, higher for the lower frequencies (0,5 for 0,3 Hz), and lower for the higher frequencies (0,1 for 0,8 Hz).

Animals↗
PubMed1987

Eye movements evoked by microstimulation in the flocculus of the alert macaque.

We have used microstimulation in the floccular cortex of alert monkeys to study the role of the cerebellar flocculus in the control of slow eye movements and the representation of eye movement direction in the flocculus. Eye movements having peak velocities of less than 15 deg/s, sometimes accompanied by rapid eye movements, were evoked using trains of current pulses (22 microA or less). The initial slow eye movement was designated Phase I. By restricting current spread to specific layers of the flocculus, evidence was obtained that Phase I was caused by the activation of molecular layer elements; it appeared to reflect the suppression of Purkinje cell activity. Phase I, therefore, probably represents the best estimate of the effect of changing Purkinje cell activity in a limited region. Phase I ended either during the pulse train or after the end of the pulse train; following the end of Phase I, the eye movement reversed its direction. Again by stimulating various layers, the eye movement following the reversal (Phase II and the off-response) was attributed to activation of Purkinje cell axons and other elements, including floccular afferents, in the granular layer and white matter. Phase I eye movements in all directions were evoked from the flocculus. Homogeneous zones with respect to eye movement direction were approximately 300 micron in diameter. When the cortex was represented as a two-dimensional sheet, a large number of zones corresponding to different directions of Phase I were observed.

Animals↗
PubMed1991

[Abnormal vergence eye movement during eyelid closure caused by a pineal tumor].

A case with abnormal eye movement induced by eyelid closure and selective paralysis of downward gaze was reported. CT scan and MRI imaging revealed a pineal tumor with bilateral involvement of the thalamomesenchephalic junctions without obvious damage to the posterior commissure. Histopathologically, the tumor was a germinoma. The pupillary light reflex was absent and near reflex was reduced. Lightning eye movement, skew deviation and convergence-retraction nystagmus were observed. The horizontal eye movement was normal in both eyes. The eye did not move downward below the level of direct forward gaze spontaneously or on attempted downward gaze. Downward vestibulo-ocular reflex was absent. Bilateral abnormal vergence eye movement with alternating convergence and divergence was observed during eyelid closure. The cycle of the abnormal eye movement was about 3Hz and there was no fast phase. The abnormal eye movement was not observed in the darkened room with both eyes open. After subtotal removal and radiation therapy of the pineal tumor, the abnormal eye movement disappeared.

Adult↗
PubMed1986

Saccadic eye movements as a measure of residual effects: temazepam compared with other hypnotics.

Eye movements are classified into two categories: quickly running saccades and smooth pursuit movements. Saccades are fast conjugate eye movements with a preprogrammed direction, amplitude, and speed course; their purpose is to register new objects in the visual field. The duration and velocity of saccadic eye movements are very much dependent on vigilance. Comparisons were made with a number of psychometric tests [d 2 Durchstreichtest (cross out test), Viennese determination apparatus, and flicker fusion frequency] and the velocity of fast eye movements. The results of three separate investigations are presented. Standardization was undertaken in 100 healthy volunteers, 50 male and 50 female subjects aged between 20 and more than 50 years were included. In an open parallel group study, comparisons were made between various hypnotics with different half-lives (temazepam, flunitrazepam, flurazepam, and phenobarbital). There were 10 healthy volunteers in each group, and medication was taken as a single night-time dose for 7 nights. In a double-blind study, temazepam (20 mg/day) was tested against flunitrazepam (2 mg/day). Dosing lasted 7 days. A marked impairment of the saccadic eye movements was observed with flunitrazepam but not with temazepam. Of all the benzodiazepines tested, only temazepam had no influence on the parameters of the saccade test. These results can be explained by temazepam's short half-life and also by the fact that no active metabolites are formed.

Adult↗
PubMed2003

An eye-movement-contingent probe paradigm.

A new eye-movement-contingent probe task is presented in which readers' eye movements are monitored as they read sentences and respond to a probe word; the timing of the display of the probe word is dependent on fixation of a target word. The present study examined semantic priming effects. The target word was either related (doctor) or unrelated (lawyer) to the probe word (nurse), and the probe appeared 120, 250, 500, or 750 msec after the reader first fixated on the target word. When the probe word appeared (in the location of the target word), the rest of the sentence disappeared until the participant named the probe word. Then the sentence reappeared, and the participant continued reading the sentence. Naming times to the probe word were recorded, as was sentence reading time and the eye movement behavior relative to the onset of the probe word. Priming effects were observed, since probe reaction time to related probes was faster than that to unrelated probes. Ways in which this paradigm can be used to study various issues in language processing are discussed.

Eye Movements↗