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PubMed1986

Latency of eye movement and other REM sleep parameters in bipolar depression.

Parameters of rapid eye movement (REM) sleep were measured in 10 endogenous bipolar depressive drug-free patients and in healthy subjects. A significant reduction of eye movement latency and larger standard deviations in the values for activity and density of eye movement were found in the depressed patients. The method applied in this study, embodying an aspect of cybernetic theory in pattern recognition, proved very useful for the elaboration of the biological data.

Adult↗
PubMed2004

Similar kinematic properties for ocular following and smooth pursuit eye movements.

Ocular following (OFR) is a short-latency visual stabilization response to the optic flow experienced during self-motion. It has been proposed that it represents the early component of optokinetic nystagmus (OKN) and that it is functionally linked to the vestibularly driven stabilization reflex during translation (translational vestibuloocular reflex, TVOR). Because no single eye movement can eliminate slip from the whole retina during translation, the OFR and the TVOR appear to be functionally related to maintaining visual acuity on the fovea. Other foveal-specific eye movements, like smooth pursuit and saccades, exhibit an eye-position-dependent torsional component, as dictated by what is known as the "half-angle rule" of Listing's law. In contrast, eye movements that stabilize images on the whole retina, such as the rotational vestibuloocular reflex (RVOR) and steady-state OKN do not. Consistent with the foveal stabilization hypothesis, it was recently shown that the TVOR is indeed characterized by an eye-position-dependent torsion, similar to pursuit eye movements. Here we have investigated whether the OFR exhibits three-dimensional kinematic properties consistent with a foveal response (i.e., similar to the TVOR and smooth pursuit eye movements) or with a whole-field stabilization function (similar to steady-state OKN). The OFR was elicited using 100-ms ramp motion of a full-field random dot pattern that moved horizontally at 20, 62, or 83 degrees/s. To study if an eye-position-dependent torsion is generated during the OFR, we varied the initial fixation position vertically within a range of +/-20 degrees . As a control, horizontal smooth pursuit eye movements were also elicited using step-ramp target motion (10, 20, or 30 degrees/s) at similar eccentric positions. We found that the OFR followed kinematic properties similar to those seen in pursuit and the TVOR with the eye-position-dependent torsional tilt of eye velocity having slopes that averaged 0.73 +/- 0.16 for OFR and 0.57 +/- 0.12 (means +/- SD) for pursuit. These findings support the notion that the OFR, like the TVOR and pursuit, are foveal image stabilization systems.

Animals↗
PubMed1996

Coordinate system for learning in the smooth pursuit eye movements of monkeys.

Learning was induced in smooth pursuit eye movements by repeated presentation of targets that moved at one speed for 100 msec and then changed to a second, higher or lower, speed. The learned changes, measured as eye acceleration for the first 100 msec of pursuit, were largest in a "late" interval from 50 to 80 msec after the onset of pursuit and were smaller and less consistent in the earliest 30 msec of pursuit. In each experiment, target motion in one direction consisted of learning trials, whereas target motion in the opposite (control) direction consisted of trials in which targets moved at a constant speed for the entire duration of the trial. Under these conditions, the learning did not generalize to the control direction. For target motion in the learning direction, the changes in pursuit generalized to responses evoked by targets moving at speeds ranging from 15 to 45 degrees/sec as well as to targets of different colors and sizes. Although learning was induced at the initiation of pursuit, it generalized to the response to image motion in the learning direction when it was presented during pursuit in the learning direction. However, learning did not generalize to the response to image motion in the learning direction when it was presented during pursuit in the control direction. The results suggest that the learning does not occur in purely sensory or motor coordinates but in an intermediate reference frame at least partly defined by the direction of eye movement. The selectivity of learning provides new evidence for a previously hypothesized neural "switch" that gates visual information on the basis of movement direction. This selectivity also suggests that the locus of pursuit learning is in pathways related to the operation of the switch.

Animals↗
PubMed1986

Eye-movement-dependent loss in vision and its time course during vergence.

The attenuation of vision that has long been known to accompany saccadic eye movement has a significant component that is not attributable to visual masking or image smear, and this suppression of vision is now associated with nonsaccadic movement. The purpose of the present experiment was to determine the time course of visual suppression during a vergence eye movement. Suppression was evaluated psychophysically in human observers by measuring their loss of sensitivity to a brief, full-field decrement of light during 6 degrees-9 degrees convergence. Vergence-related suppression was similar in total duration and amplitude to saccadic and blink-related suppression. Since these other forms of oculomotor activity are vastly different in speed and total duration, it is unlikely that suppression results directly from the activity itself. Instead, these results support the hypothesis that a common, more centrally originating, suppression of vision occurs during eye movements, including saccades, eyeblinks, and vergence. Thus, while vision during eye movements can often be reduced through masking and smearing effects, the movement-dependent visual suppression measured in these experiments is a more generally occurring event.

Convergence, Ocular↗
PubMed1985

Eye movement differences between dyslexics, normal, and retarded readers while sequentially fixating digits.

The eye movements of 13 dyslexics, 10 normal, and 16 retarded readers were recorded while they sequentially fixated 7 equidistantly spaced digits from left to right (L----R) and right to left (R----L). This nonreading task simulated the sequential motor components of the reading process. Dyslexics and their controls were selected on the basis of comprehensive and quantifiable criteria. All three groups were of the same chronological age. The dyslexics and retarded readers had also the same reading difficulties, but the causes of their problems were different. Dyslexics made significantly more regressions than the normal or the retarded readers in both directions (L----R and R----L). These results were in line with the ones reported in similar studies and suggest that the dyslexics' erratic eye movements and their excessive number of regressions are present even in nonreading, nonverbal sequential tasks. It may, therefore, be possible to use the eye movement records from nonreading sequential tasks for the objective diagnosis of dyslexia. As such tasks do not depend on reading, they may even be used before reading age.

Adolescent↗
PubMed2001

Systematic eye movements do not account for the perception of motion during attentive tracking.

It has been suggested that attention can disambiguate stimuli that have equal motion energy in opposite directions (e.g. a counterphasing grating), such that a clear motion direction is perceived. The direction of this movement is determined by the observer and can be changed at will. Assuming that the responses of front-end motion detectors are equal for the two opponent directions, it has been proposed that the unambiguous motion perceived with attentive tracking arises from an independent mechanism that monitors the shifts of attention directed to the moving feature of interest. However, while perceiving motion under attentive tracking conditions, observers often report a strong impression that they are making eye movements. In this study, we investigated whether systematic eye movements are present during attentive tracking and, as a result, could be responsible for the subjective experience of movement. We had observers track an object in smooth motion, apparent motion and ambiguous motion, either with eye movements or with attention. The results show that there are negligible eye movements during attentive tracking, which are neither systematic nor correlated with the stimulus. Given that neither eye movements nor retinal image motion can account for subjectively perceived motion, as well as the absence of any other plausible explanation, we find it tempting evidence for an earlier suggestion that the percept of movement must arise from a specialized mechanism.

Attention↗
PubMed2004

Central and peripheral visual interactions in disparity-induced vergence eye movements: I. Spatial interaction.

PURPOSE: To evaluate the interaction between central and peripheral disparities in the initiation of vergence eye movements. METHODS: Eye movements were recorded in eight normal subjects using an infrared limbus tracker. Three-dimensional visual stimuli were back projected onto a tangent screen by using two liquid crystal display (LCD) projectors through crossed polarizers. The central target was a vertical bar, which always jumped from 2 to 1 m. The peripheral target was a random-dot pattern that jumped from 2 to 0.75, 1, or 1.5 m (near planes), 2 m (no change), or 3 m (far plane) simultaneously with the central target jump. Latency, amplitude at 150 ms, and average amplitude over 1 to 2 seconds after vergence onset; peak velocity; and the main-sequence relationship of the initial vergence response were calculated. How far the central target appeared to jump was scored subjectively. RESULTS: In half of the subjects, there was a clear effect of the peripheral disparity on the dynamics of the vergence response to the central disparity. The amplitude of vergence at 150 ms, as an index of open-loop gain, was significantly greater when the peripheral target moved closer, but steady state amplitude (average during 1-2 seconds) did not change, and the vergence latency was significantly greater when the peripheral target jumped away. There was no obvious relationship between the perceived amount of movement of the central target and the parameters of the dynamic properties of the vergence response. CONCLUSIONS: Peripheral disparity can modulate the dynamics of the initial vergence response to a central disparity and is probably independent of the perception of motion in depth.

Adult↗
PubMed2005

Optimal eye movement strategies in visual search.

To perform visual search, humans, like many mammals, encode a large field of view with retinas having variable spatial resolution, and then use high-speed eye movements to direct the highest-resolution region, the fovea, towards potential target locations. Good search performance is essential for survival, and hence mammals may have evolved efficient strategies for selecting fixation locations. Here we address two questions: what are the optimal eye movement strategies for a foveated visual system faced with the problem of finding a target in a cluttered environment, and do humans employ optimal eye movement strategies during a search? We derive the ideal bayesian observer for search tasks in which a target is embedded at an unknown location within a random background that has the spectral characteristics of natural scenes. Our ideal searcher uses precise knowledge about the statistics of the scenes in which the target is embedded, and about its own visual system, to make eye movements that gain the most information about target location. We find that humans achieve nearly optimal search performance, even though humans integrate information poorly across fixations. Analysis of the ideal searcher reveals that there is little benefit from perfect integration across fixations--much more important is efficient processing of information on each fixation. Apparently, evolution has exploited this fact to achieve efficient eye movement strategies with minimal neural resources devoted to memory.

Brain↗
PubMed2004

Eye movements when reading disappearing text: is there a gap effect in reading?

Readers' eye movements were monitored when they read either normal sentences or sentences with masked or disappearing text (in which the fixated word disappeared or was masked after 60 ms). The goals of the research were to investigate (1) whether a gap effect occurred in reading and (2) the influence of linguistic and visual factors on oculomotor control. The results of a number of global analyses of eye movements under disappearing text conditions clearly demonstrated that there is no gap effect in reading. However, comparative analyses across a number of local measures in the experiments indicated that cognitive/lexical processes, as well as the continual uptake of visual information, influence eye movement control during reading. A persistent visual object throughout fixation caused refixations and even when a fixated word had disappeared (or been masked), there were significant effects of word frequency and word length.

Cognition↗
PubMed2005

Perceived motion direction during smooth pursuit eye movements.

Although many studies have been devoted to motion perception during smooth pursuit eye movements, relatively little attention has been paid to the question of whether the compensation for the effects of these eye movements is the same across different stimulus directions. The few studies that have addressed this issue provide conflicting conclusions. We measured the perceived motion direction of a stimulus dot during horizontal ocular pursuit for stimulus directions spanning the entire range of 360 degrees. The stimulus moved at either 3 or 8 degrees/s. Constancy of the degree of compensation was assessed by fitting the classical linear model of motion perception during pursuit. According to this model, the perceived velocity is the result of adding an eye movement signal that estimates the eye velocity to the retinal signal that estimates the retinal image velocity for a given stimulus object. The perceived direction depends on the gain ratio of the two signals, which is assumed to be constant across stimulus directions. The model provided a good fit to the data, suggesting that compensation is indeed constant across stimulus direction. Moreover, the gain ratio was lower for the higher stimulus speed, explaining differences in results in the literature.

Adolescent↗
PubMed1991

The mechanism of prediction in human smooth pursuit eye movements.

1. Experiments have been conducted on human subjects to determine the role of prediction in smooth eye movement control. Subjects were required to actively pursue a small target or stare passively at a larger display as it moved in the horizontal plane. 2. Target motion was basically periodic, but, after a random number of cycles an unexpected change was made in the amplitude, direction or frequency of target motion. Initially, the periodic stimulus took the form of a square waveform. In subsequent experiments, a triangular or sawtooth waveform was used, but in order to examine the timing of the response in relation to stimulus appearance, the target was tachistoscopically illuminated for 40-320 ms at the time that it passed through the mid-line position. 3. When subjects either actively pursued the target or stared passively at the larger display a characteristic pattern of steady-state eye movement was evoked composed of two phases, an initial build-up of eye velocity that reached a peak after 200 ms, followed by a decay phase with a time constant of 0.5-2 s. The build-up phase was initiated prior to target displacement for square-wave motion and before onset of target illumination for other waveforms. 4. The peak eye velocity evoked gradually increased over the first two to four cycles of repeated stimulation. Simultaneously, the response became more phase advanced, the reaction time between stimulus onset and the time at which peak velocity occurred decreasing from an average of 300 to 200 ms for triangular waveform stimuli. 5. When there was a sudden and unexpected change in amplitude and direction of the stimulus waveform, the eye movement induced had a peak velocity and direction that was inappropriate for the current visual stimulus, but which was highly correlated with the features of the preceding sequence in the stimulus. 6. When there was a sudden change in the frequency of the stimulus waveform the predictive eye movement was induced with a timing appropriate to the periodicity of the previous sequence but inappropriate to the new sequence. 7. The results indicate that prediction is carried out through the storage of information about both the magnitude and timing of eye velocity. The trajectory of the averaged eye velocity response was similar in form irrespective of the duration of target exposure or basic stimulus frequency, suggesting that the predictive estimate is released as a stereotyped volley of constant duration but varying magnitude under the control of a periodicity estimator.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗
PubMed1993

Hemispheric preference and lateral eye movements evoked by bilateral visual stimuli.

This study investigated the relationship between the direction of lateral eye shifts evoked by bilateral visual stimulation, on the one hand, and verbal vs visuospatial performance, on the other. In males a negative correlation was found between verbal relative to spatial accuracy and the ratio of leftward eye movements. No such relationship was found in females. Additionally, in males body mass index was smaller for those who displayed a greater ratio of leftward eye movements. It was concluded that visually evoked lateral eye shifts might reflect hemispheric preference, similarly as lateral eye movements obtained during the widely used questioning procedure. However, the procedure used in this study for evoking lateral eye shifts seems to be free of some methodological problems of the traditional procedure and is more easy to standardize.

Adolescent↗
PubMed2000

A comparison of video and magnetic search coil recordings of mouse eye movements.

Interest in connecting molecular biology and behavior is motivating research into the eye movements of mice. Unfortunately, recording eye movements in this diminutive animal is technically difficult. We present the first method for obtaining calibrated video oculography, and contrast the results with simultaneously obtained scleral search coil recordings in C57BL/6 pigmented mice. We determined the distance of the pupil from the center of corneal curvature, based upon relative motions of the pupil and corneal reflections during camera movements, and used the distance to convert subsequent video measurements of pupil motion to eye rotation. We recorded responses during sinusoidal rotation (0.1-1.6 Hz) in the light, by video prior to search coil implantation, and by video and search coil simultaneously following implantation. Pre-implantation, video-derived gains ranged from 0.86+/-0.03 (mean+/-SD) at 0.1 Hz to 0.95+/-0.03 at 0.8 Hz. Phase progressed monotonically from -3.1+/-2. 6 degrees (eye leads head) at 0.1 Hz to +5.9+/-1.1 degrees at 1.6 Hz. Coil implantation reduced the range of video-derived gains to 0. 64-0.79. This reduction reflects disruption of normal behavior by the coil. Coil data confirmed the video results. Video and search coil techniques each have advantages. Specific precautions are required when designing and interpreting experiments using the coil technique.

Animals↗
PubMed1978

Latency to respond and conjugate lateral eye movements: a methodological and theoretical note.

The relationship between latency to first response and lateral eye movements was investigated for 52 preschool and primary grade children. Latency to respond correlated significantly with number of eye movements observed for each child. Significantly greater latency occurred for spatial questions than for verbal reasoning questions. Methodological and theoretical implications of latency to first response in relation to the study of conjugate lateral eye movements are briefly described.

Child↗
PubMed2005

Prediction in the timing of pursuit eye movement initiation revealed by cross-axis vestibular-pursuit training in monkeys.

The smooth-pursuit system interacts with the vestibular system to maintain the image of a moving target on the fovea. Efficient tracking performance requires information about the velocity and the initiation of target motion. Previous studies in monkeys have shown that training with orthogonal pursuit and whole body rotation results in adapted eye movement direction during chair rotation. In addition, the latency of the pursuit shortens and initial eye velocity increases in a task-dependent manner. To examine whether these adapted eye movements are predictive pursuit, we studied whether our monkeys could predict the timing of smooth eye movement initiation during chair rotation. Two young Japanese monkeys were rotated horizontally in a trapezoidal waveform (20 degrees/s, +/-10 degrees) with random inter-trial intervals. A laser spot was moved vertically with the same trajectory at a constant delay ranging from 100 to 700 ms after the onset of the chair motion. The monkeys were required to pursue the spot. After this training, the latencies of pursuit eye movements following the onset of chair motion were examined in the presence of the target motion. The target was also briefly (for 500-700 ms) extinguished at 80 ms after the onset of chair rotation. Pursuit eye movements after training were initiated before the onset of target motion and the latencies were proportional to the delays used for training. The latencies and response magnitudes of pursuit with or without target blanking were similar. The auditory-pursuit training did not induce an initial pursuit response similar to that induced by vestibular-pursuit training. These results indicate that smooth eye movements during the chair rotation after the vestibular-pursuit training included a predictive pursuit component. The monkeys' estimate of the delays revealed by the latencies of pursuit was shorter by 22-36% than the actual delays.

Adaptation, Physiological↗
PubMed1997

Eye-movements and visual imagery: a working memory approach to the treatment of post-traumatic stress disorder.

It has been claimed that the symptoms of post-traumatic stress disorder (PTSD) can be ameliorated by eye-movement desensitization-reprocessing therapy (EMD-R), a procedure that involves the individual making saccadic eye-movements while imagining the traumatic event. We hypothesized that these eye-movements reduce the vividness of distressing images by disrupting the function of the visuospatial sketchpad (VSSP) of working memory, and that by doing so they reduce the intensity of the emotion associated with the image. This hypothesis was tested by asking non-PTSD participants to form images of neutral and negative pictures under dual task conditions. Their images were less vivid with concurrent eye-movements and with a concurrent spatial tapping task that did not involve eye-movements. In the first three experiments, these secondary tasks did not consistently affect participants' emotional responses to the images. However, Expt 4 used personal recollections as stimuli for the imagery task, and demonstrated a significant reduction in emotional response under the same dual task conditions. These results suggest that, if EMD-R works, it does so by reducing the vividness and emotiveness of traumatic images via the VSSP of working memory. Other visuospatial tasks may also be of therapeutic value.

Adult↗
PubMed1976

Smooth pursuit eye movements, attention, and schizophrenia.

In previous studies, smooth pursuit eye movements (SPEM) have been shown to be disordered in about 70% of schizophrenics and about 45% of their first-degree relatives. In this report, the role of attention in these eye movements is addressed in three experiments (using as subjects schizophrenics, their first-degree relatives, and normals administered chloral hydrate) that recruit focused attention to the task. These studies show that voluntary attention in the form of inattention, "heedless negligence," or failure to cooperate, is not the specific attentional quality that is disordered in SPEM of schizophrenics and their relatives. Rather, the data both indicate that nonvoluntary attending is specifically disordered in these persons, and implicate a neurophysiological substrate that can be described as a failure of inhibitory, synchronizing integrating systems which may be located in the brain stem.

Adult↗
PubMed1982

A procedure for the analysis of nystagmus and other eye movements.

A simple procedure has been developed for the computer analysis of nystagmus and other eye movements using the superior pattern recognition capabilities of the human operator to distinguish between fast- and slow-phase eye movements. The basis of the procedure is that the operator can set up threshold limits around an expected slow-phase eye velocity waveform through the use of cursor facilities. Points lying outside the threshold limits are recognised as fast-phase eye movements and discarded. Various least-squares curve-fitting procedures are then used to establish the relationship between the oculomotor response and the stimulus waveform. Examples are given of analysis procedures for both periodic and transient responses of the vestibulo-ocular reflex. The method is particularly useful for the analysis of responses to voluntary head movement in which slow-phase velocity frequently approaches that of the fast-phase components.

Computers↗