Showing papers on "Eye tracking published in 1987"

Visual Motion Processing and Sensory-Motor Integration for Smooth Pursuit Eye Movements

Abstract: The function of smooth pursuit is to keep the fovea pointed at a small visual target that moves smoothly across a patterned background. Chemical lesions, single cell recordings, and behavioral measures have shown that the cortical motion processing pathways form the afferent limb for pursuit. Important areas include at least the striate cortex and the middle temporal visual area, and probably the medial superior temporal visual area and the posterior parietal cortex. We argue that the visual inputs are transmitted through a simple sensory motor interface in the pons, to the efferent limb in the brain stem and cerebellum. The efferent limb uses neural velocity memory to maintain pursuit automatically. We present evidence that the velocity memory is provided, at least in part, by eye velocity positive feedback between the flocculus of the cerebellum and the brain stem. Finally, we use a computer model to show how the maintenance of pursuit can be simulated on a millisecond time scale. The structure and internal elements of the model are based on the biological experiments reviewed in our paper. In the past five years, progress on the neural basis of pursuit eye movements has been rapid. Several areas of research have made substantial contributions, by using combinations of new and conventional methods. Many of the pathways that contribute to pursuit have been identified, and their physiological activity and functions are becoming understood. Continuing progress promises to yield an understanding of one specific form of visually guided movement, at the level of neuronal circuits and behavior, in the primate.

Visual computation and saccadic eye movements: a theoretical perspective

Abstract: A simple instance of parallel computation in neural networks occurs when the eye orients to a novel visual target. Consideration of target-elicited saccadic eye movements opens the question of how spatial position is represented in the visual pathways involved in this response. It is argued that a point-for-point retinotopic coding of spatial position (the 'local sign' approach) is inadequate to account for the characteristics of the response. An alternative approach based on distributed coding is developed.

Saccadic eye movements and the perception of visual direction

Abstract: The extant research literature concerning intrasaccadic stimuli implies that if a spot of light is flashed in the dark during a saccadic eye movement, one should subsequently look for the light in one direction while professing to see it lying in another. This paper accounts for this paradox in terms of two hypothesized varieties of sensed eye orientation, one estimating actual eye orientation (efference copy) and the other corresponding to intended eye orientation (afference copy).

Blink-related eye movements.

Abstract: Eye movements that accompany a blink have been measured in human subjects by the use of a visual-persistence method. With straight-ahead binocular viewing, each eye typically rotates nasalward and downward 1-2 deg during the closing phase of a blink. These eye movements are more rapid than the lid movements as recorded by high-speed photography. In fact, the eyes have already completed their initial rotation and started back again before the lids are fully closed. With off-center viewing, a blink causes each eye to rotate toward its primary position of regard. Indeed, if the eye is already in that position when the blink starts, the eye moves very little. With eyelids taped open, an eye tracker can be used, and records confirming the visual persistence tracings are obtained. Sequential photography of the cornea in profile reveals that the eye moves inward and back out again during a blink. The amplitude of this retraction is typically less than 1 mm; and its time course, slower than that of the rotational eye movements, parallels the closure and opening of the lids. In normal conditions of viewing there is no evidence of conjugate saccades, or of any large, upward rotation of the eyes (Bell's phenomenon) that was once believed to take place during a blink.

Eye Gaze & Communication in a Deaf Classroom

Abstract: Eye gaze plays a significant role in making communication effective. Eye gaze behavior of two teachers of deaf children is examined as it helps (or does not) to regulate turn-taking during story reading. Eye gaze signals inviting individual and group response are described in use to initiate a story reading, communicate with a particular student, invite response from any in a group, and to ask a question, use a book in class, and handle a distraction or interruption during the reading.

Effect of eye movements on dynamic equilibrium.

Abstract: The purpose of this study was to determine whether visual improvement of balance varies depending on the movement of the eye. Three movements were compared: static visual fixations, saccadic eye movements, and smooth pursuit eye movements. The subjects in this study were 35 healthy female volunteers. Balance was defined as the subjects' ability to maintain their equilibrium while keeping the unstable platform on which they stood within 5 degrees of the horizontal plane. The testing protocol consisted of five recorded practice trials, during which the subjects tried to maintain their balance without any visual instructions, and nine experimental trials, during which they tried to maintain their balance while visually following a videotaped target light projected onto a screen. The target light was sequenced randomly to remain stationary, move in a continuous horizontal path, or alternately jump between right and left. Data were analyzed using a one-way multivariate analysis of variance for repeated measures. A significant effect of vision on balance was found. The t tests for correlated samples revealed that time in balance during visual fixations and saccades was significantly longer than during tracking eye movements. We, therefore, concluded that tracking eye movements have a negative effect on balance. This information can be useful in treating patients with balance problems. For example, instructing patients to fixate visually on an object may aid their stability. Visual tracking of a moving limb, however, may impair a patient's stability.

Definition of gazing point for picture analysis and its applications

Abstract: The authors have been analyzing images by eye movement. For this purpose, it is necessary to decompose the eye movement into a component to accept information from a gazed object and a component to shift the gazing point. The point considered in the foregoing is called the gazing point, which is defined in this paper based on the property of the pursuit eye movement. Eye movement velocity of 5 deg/s is used as the threshold to separate the two components. As a result, it is made possible to separate clearly the eye movement into the gazing point component and the shift between the gazing point. A vision analyzer based on this definition of the gazing point was developed, which can analyze comprehensively the eye movement in real-time. As an example of the application of the vision analyzer, the difference of the eye movement in watching the VDT image and the usual dynamic picture is analyzed. Furthermore, as an application to the analysis of art, an experiment was made as a reference material for the analysis of Sharaku's ukiyo-e painting. The results of experiments are described, indicating that the definition of the gazing point is adequate.

Eye Movement Control during Reading: I. The Location of Initial Eye Fixations on Words. Technical Report No. 406.

Abstract: Sixty-six college students read two chapters from a contemporary novel while their eye movements were monitored. The eye movement data were analyzed to identify factors that influence the location of a reader's initial eye fixation on a word. When the data were partitioned according to the location of the prior fixation (i.e. launch site), the distribution of fixation locations on the word (i.e. landing site distribution) was highly constrained, normal in shape, and not influenced by word length. The locations of initial fixations on words can be accounted for on the basis of five principles of perceptuo-oculomotor control: a word-object has a specific functional target location, a saccadic range error occurs that produces a systematic deviation of landing sites from the functional target location, the saccadic range error is reduced somewhat for saccades that follow longer eye fixations, there exists perceptuo-oculomotor variability that is a second, nonsystematic source of variation in landing sites, and the perceptuo-oculomotor variability increases with distance of the launch site from the target.

A model for dysfunctions in smooth pursuit eye movement.

Abstract: In this paper, I have introduced and solved a simple deterministic model of eye tracking that produces rich dynamical behavior. Some of its main features, notably the existence of a chaotic regime, are reminiscent of the anomalies reported in smooth pursuit eye tracking experiments with schizophrenia patients. By obtaining the state diagram of such a model as a function of target frequency and amplitude, we showed the existence of a chaotic regime characterized by a strange attractor in phase-space and associated random velocity arrests in the eye dynamics. Moreover, the power spectrum contains features similar to those reported in the literature. The correctness of this model could in principle be determined by performing experiments where the target parameters (i.e., amplitude and frequency) could be varied in a systematic manner and by taking Poincare maps from the corresponding time series. Although the present status of such experiments prevents us from verifying the validity of the model, the available data does not seem to contradict the main predictions. Furthermore, we showed that the inevitable noise expected to be present in actual experiments would only enhance the observability of our predictions. If this model were proven incorrect, then the focus of research into mechanisms will have to shift into a search for an intrinsic source of the fluctuations. If, on the other hand, this deterministic theory has any validity, it will point to the nonlinearities in eye tracking mechanisms as the main culprits for the observed anomalies.

Stimulator for eye tracking oculometer

Abstract: An electronic apparatus for stimulating or actuating an eye sensing oculometer system with simulated eye movement signals that are stable, predetermined, and repeatable. The simulated signals are electrically coupled to an oculometer signal input port in lieu of video signals normally received from an eye viewing camera. Optical images representing infra red reflections from the retina and the cornea portions of the oculometer user's eye are simulated by the apparatus; movement of these images in a computer controlled pattern is contemplated and is emulated by simple operator electable patterns in the disclosed apparatus. The presence of noise signals and eye imperfections are contemplated in the stimulating apparatus.

Vision testing and/or training apparatus and method

Abstract: Vision testing and training apparatus and methods employ a rotatable turntable which is provided with a plurality of openings. As the turntable rotates, pegs are inserted into or removed from the openings by an individual who desires to test and/or improve his or her eye/hand coordination. By providing the apparatus with a rotatable disc containing vision-testing indicia in the form of printed letters and/or numbers, the apparatus can be used to improve one's eye tracking skills but not necessarily eye/hand coordination.

A micro computer based system for the analysis of saccadic eye movements

Abstract: Publisher Summary This chapter discusses a microcomputer-based system for the analysis of saccadic eye movements The examination of eye movements is one aspect of a detailed study of reading in school children Eye movements are recorded onto a Racal FM tape recorder using the sclera-reflectance technique during simple sequential tracking tasks and during the silent reading of a prose passage The main aim of the project is to design a microcomputer-based system to retrieve the recorded eye movements and to display them on a monitor for selection by an operator to be analyzed by the computer The analysis comprises the identification and quantification of fixations and saccadic movements The results of the analysis are stored in a form suitable for subsequent transmission to a mainframe computer for further statistical analysis The method used is graphically based and involves an operator moving a bar across the screen, controlled by the movement keys on the computer The advantage of this method is that it smooths out the data and is much less sensitive to locally noisy areas of trace The disadvantage is that considerably longer time is taken for computation

Effect of visual input in motor program of saccades

Abstract: Publisher Summary This chapter focuses on the effects of visual input in a motor program of saccades. It also describes whether motor programs of eye movements are modified by visual input. The experiments explained in the chapter are carried out on one monkey trained to track targets. Horizontal and vertical components of eye movements are derived using search-coil and magnetic-field techniques. The analysis of eye movements is done off-line by a graphic unit. Analogue signals are converted into digital signals using a sample frequency and are subsequently filtered to a lower frequency by a low-pass filter. The eye movements are recorded in darkness, under laboratory lighting, and between targets. The chapter shows that there is no substantial difference in distribution between dark and lab light. However, in the target situation the irregular pattern is absent. This suggests that visual input modifies motor programs.

Looking, moving and seeing

Abstract: Why are there eye movements? To shift images across the retina. There is a system for fast centering of an image on the retina, a system for tracking a slowly moving image, and a vestibular system for maintaining the same field of view. How is the perception of the visual world rendered stable in the face of all these eye movements and yet the movement of particular objects within the environment is accurately seen?

Measuring Symptoms in Parkinson’s Disease with a tracking device

Abstract: A simple computer based visual tracking device is presented which allows to measure different motor performances in Parkinsonian patients. The device uses a computer to drive the reference signal which is tracked by the thumb movements of the patient. The computer provides the signals for different tracking conditions, records the tracking performance and analyses the recorded data. Three examples are used to show how the device can be used to measure different Parkinsonian symptoms.

On-line registration of eye tracking movements in the a.c. mode for the computation of positional deviations

Abstract: This paper summarizes and discusses methodology and recent findings of a series of studies on eye tracking movements in psychotic patients, alcohol abusers and normals, studies employing alternating current (a.c.) amplification for the computation of positional deviations. An on-line system is described involving the use of an electronic pendulum, there being two different tasks, a less attention demanding (following a red light only) and a more attention demanding one (having to press a button each time the light changes to green). Eye tracking using a.c. amplification and a high-pass filter with a long time constant (corresponding to 0.16 Hz) is seen to provide excellent opportunities for the study of multilevel eye-tracking phenomena. A trial with the on-line equipment was designed for exploring, by means of spectography, what frequency components might be connected with the general findings, reported in earlier studies for macro-level tracking to be smoother under more attention demanding conditions and for microtremor rate to increase as cognitive strain increases. The frequency bands of the spectrogram comprising lower frequencies up to about 15–25 Hz were found to decrease in all subjects (n=6; all males, three of them health care personnel and three alcohol abusers) in the more attention demanding as compared to the less attention demanding condition, indicating tracking to be better during the former condition. At the same time higher-frequency bands generally increased during the more attention demanding condition as compared to the less attention demanding condition, the rise here occurring parallel to a corresponding rise in microtremor rate.

Pursuit eye movements evoked during eye tracking of a target moved by the observer

Abstract: Steinbach によると, 観察者自身が自分の手で視標を動かし, それを眼で追う場合には, 観察者の意志とは無関係に動かされた視標を追う場合に比べて, 随従眼球運動が大きく現れる. 彼は, この原因として手を動かすための遠心性信号が動眼系に伝達されるためと考えた. ところで, アイトラッキングにおける追従性能は, 視覚だけを手がかりとする場合でも, その動きが予測可能 (規則的) な場合はそうでない場合に比べてよくなることが知られている. 本論文は, Steinbach の結果が単に視標運動に対する予測性の大小によるものなのか, あるいはそれとは異なった原因によるものなのかを明らかにしようとするものである. 実験の結果, 自分で動かした視標を追跡する場合の追従性能の向上は, 視標の動きが予測可能である場合のそれと全く同じ性質をもつものであることがわかった.