Types Of Eye Movements Research Articles

In vivo retinal imaging for fixational eye motion detection using a high-speed digital micromirror device (DMD)-based ophthalmoscope.

Retinal motion detection with an accuracy of 0.77 arcmin corresponding to 3.7 µm on the retina is demonstrated with a novel digital micromirror device based ophthalmoscope. By generating a confocal image as a reference, eye motion could be measured from consecutively measured subsampled frames. The subsampled frames provide 7.7 millisecond snapshots of the retina without motion artifacts between the image points of the subsampled frame, distributed over the full field of view. An ophthalmoscope pattern projection speed of 130 Hz enabled a motion detection bandwidth of 65 Hz. A model eye with a scanning mirror was built to test the performance of the motion detection algorithm. Furthermore, an in vivo motion trace was obtained from a healthy volunteer. The obtained eye motion trace clearly shows the three main types of fixational eye movements. Lastly, the obtained eye motion trace was used to correct for the eye motion in consecutively obtained subsampled frames to produce an averaged confocal image correct for motion artefacts.

Automatic identification of eye movements using the largest lyapunov exponent

Abstract The study of eye movements has been increasing over the past decade. It is considered that eye movements, mainly saccades and blinks, provide significant information for cognitive and visual processes of the observers. Saccades and blinks are high velocity eye movements. In this paper, the automatic identification of saccades and blinks, as well as their onset and offset, is proposed based on a novel implementation of nonlinear dynamics using the Largest Lyapunov Exponent and the logarithm of the divergence. The Largest Lyapunov Exponent detection method was tested on 25,000 saccades and 2,366 blinks, detecting with high accuracy and precision both types of eye movements. The Largest Lyapunov Exponent detection method was compared against two other existing techniques for blink and saccade identification, showing advantageous performance.

Joint Learning of Binocularly Driven Saccades and Vergence by Active Efficient Coding.

This paper investigates two types of eye movements: vergence and saccades. Vergence eye movements are responsible for bringing the images of the two eyes into correspondence, whereas saccades drive gaze to interesting regions in the scene. Control of both vergence and saccades develops during early infancy. To date, these two types of eye movements have been studied separately. Here, we propose a computational model of an active vision system that integrates these two types of eye movements. We hypothesize that incorporating a saccade strategy driven by bottom-up attention will benefit the development of vergence control. The integrated system is based on the active efficient coding framework, which describes the joint development of sensory-processing and eye movement control to jointly optimize the coding efficiency of the sensory system. In the integrated system, we propose a binocular saliency model to drive saccades based on learned binocular feature extractors, which simultaneously encode both depth and texture information. Saliency in our model also depends on the current fixation point. This extends prior work, which focused on monocular images and saliency measures that are independent of the current fixation. Our results show that the proposed saliency-driven saccades lead to better vergence performance and faster learning in the overall system than random saccades. Faster learning is significant because it indicates that the system actively selects inputs for the most effective learning. This work suggests that saliency-driven saccades provide a scaffold for the development of vergence control during infancy.

Unsupervised parsing of gaze data with a beta-process vector auto-regressive hidden Markov model.

The first stage of analyzing eye-tracking data is commonly to code the data into sequences of fixations and saccades. This process is usually automated using simple, predetermined rules for classifying ranges of the time series into events, such as "if the dispersion of gaze samples is lower than a particular threshold, then code as a fixation; otherwise code as a saccade." More recent approaches incorporate additional eye-movement categories in automated parsing algorithms by using time-varying, data-driven thresholds. We describe an alternative approach using the beta-process vector auto-regressive hidden Markov model (BP-AR-HMM). The BP-AR-HMM offers two main advantages over existing frameworks. First, it provides a statistical model for eye-movement classification rather than a single estimate. Second, the BP-AR-HMM uses a latent process to model the number and nature of the types of eye movements and hence is not constrained to predetermined categories. We applied the BP-AR-HMM both to high-sampling rate gaze data from Andersson et al. (Behavior Research Methods 49(2), 1-22 2016) and to low-sampling rate data from the DIEM project (Mital et al., Cognitive Computation 3(1), 5-24 2011). Driven by the data properties, the BP-AR-HMM identified over five categories of movements, some which clearly mapped on to fixations and saccades, and others potentially captured post-saccadic oscillations, smooth pursuit, and various recording errors. The BP-AR-HMM serves as an effective algorithm for data-driven event parsing alone or as an initial step in exploring the characteristics of gaze data sets.

Differential responses of neurons in the macaque Lateral Intraparietal area to voluntary and reflexive saccades

The macaque lateral intraparietal area (LIP) is known for its involvement in processing of saccadic eye movements (Barash et al. 1991) as well as higher cognitive concepts like attention (Bisley & Goldberg 2003), value (Sugrue et al. 2004) and numerosity (Roitman 2007). While its contribution to cognitive processes is being heavily investigated, some of its basic visuo-motor functions are not described yet. We investigated the responses of 96 single neurons from area LIP of one macaque monkey to different types of fast eye movements. The neurons were first tested using regular visually guided saccade and delayed saccade paradigms. Neurons that have shown a significant (p< 0.05) peri-saccadic response were further investigated using two other categories of fast eye movements. The first category were saccades interacting with smooth pursuit eye movements (SPEM) such as visually guided saccades to moving targets and catch-up saccades that are used to re-foveate a moving target during SPEM. The second category of eye movements were fast phases of the optokinetic nystagmus (OKN). We found huge differences between the responses to the two categories. While saccades in combination with SPEM revealed similar motor responses like regular visually guided saccades (significant visuo-motor responses were preserved in all neurons), none of the neurons responded significantly during the fast phases of the OKN. However, we found a modulation of activity in OKN that consisted of a significant post-saccadic inhibition in ~50% of the investigated neurons. The inhibition was regularly followed by a brief peak in activity which may be caused by a release from inhibition. We conclude that area LIP is not primarily concerned with generation of motor commands for fast eye movements but with goal directed interaction and target selection in the visual environment (Thomas & Pare 2007). Meeting abstract presented at VSS 2017

Short-term adaptation of saccades does not affect smooth pursuit eye movement initiation.

Scrutiny of the visual environment requires saccades that shift gaze to objects of interest. In case the object should be moving, smooth pursuit eye movements (SPEM) try to keep the image of the object within the confines of the fovea in order to ensure sufficient time for its analysis. Both saccades and SPEM can be adaptively changed by the experience of insufficiencies, compromising the precision of saccades or the minimization of object image slip in the case of SPEM. As both forms of adaptation rely on the cerebellar oculomotor vermis (OMV), most probably deploying a shared neuronal machinery, one might expect that the adaptation of one type of eye movement should affect the kinematics of the other. In order to test this expectation, we subjected two monkeys to a standard saccadic adaption paradigm with SPEM test trials at the end and, alternatively, the same two monkeys plus a third one to a random saccadic adaptation paradigm with interleaved trials of SPEM. In contrast to our expectation, we observed at best marginal transfer which, moreover, had little consistency across experiments and subjects. The lack of consistent transfer of saccadic adaptation decisively constrains models of the implementation of oculomotor learning in the OMV, suggesting an extensive separation of saccade- and SPEM-related synapses on P-cell dendritic trees.

A Single-Channel EOG-Based Speller.

Electrooculography (EOG) signals, which can be used to infer the intentions of a user based on eye movements, are widely used in human-computer interface (HCI) systems. Most existing EOG-based HCI systems incorporate a limited number of commands because they generally associate different commands with a few different types of eye movements, such as looking up, down, left, or right. This paper presents a novel single-channel EOG-based HCI that allows users to spell asynchronously by only blinking. Forty buttons corresponding to 40 characters displayed to the user via a graphical user interface are intensified in a random order. To select a button, the user must blink his/her eyes in synchrony as the target button is flashed. Two data processing procedures, specifically support vector machine (SVM) classification and waveform detection, are combined to detect eye blinks. During detection, we simultaneously feed the feature vectors extracted from the ongoing EOG signal into the SVM classification and waveform detection modules. Decisions are made based on the results of the SVM classification and waveform detection. Three online experiments were conducted with eight healthy subjects. We achieved an average accuracy of 94.4% and a response time of 4.14 s for selecting a character in synchronous mode, as well as an average accuracy of 93.43% and a false positive rate of 0.03/min in the idle state in asynchronous mode. The experimental results, therefore, demonstrated the effectiveness of this single-channel EOG-based speller.

FEFsem neuronal response during combined volitional and reflexive pursuit.

Although much is known about volitional and reflexive smooth eye movements individually, much less is known about how they are coordinated. It is hypothesized that separate cortico-ponto-cerebellar loops subserve these different types of smooth eye movements. Specifically, the MT-MST-DLPN pathway is thought to be critical for ocular following eye movements, whereas the FEF-NRTP pathway is understood to be vital for volitional smooth pursuit. However, the role that these loops play in combined volitional and reflexive behavior is unknown. We used a large, textured background moving in conjunction with a small target spot to investigate the eye movements evoked by a combined volitional and reflexive pursuit task. We also assessed the activity of neurons in the smooth eye movement subregion of the frontal eye field (FEFsem). We hypothesized that the pursuit system would show less contribution from the volitional pathway in this task, owing to the increased involvement of the reflexive pathway. In accordance with this hypothesis, a majority of FEFsem neurons (63%) were less active during pursuit maintenance in a combined volitional and reflexive pursuit task than during purely volitional pursuit. Interestingly and surprisingly, the neuronal response to the addition of the large-field motion was highly correlated with the neuronal response to a target blink. This suggests that FEFsem neuronal responses to these different perturbations—whether the addition or subtraction of retinal input—may be related. We conjecture that these findings are due to changing weights of both the volitional and reflexive pathways, as well as retinal and extraretinal signals.

Active Vision: Dynamic Reformatting of Visual Information by the Saccade-Drift Cycle

Visual processing depends on rapid parsing of global features followed by analysis of fine detail. A new study suggests that this transformation is enabled by a cycle of saccades and fixational drifts, which reformat visual input to match the spatiotemporal sensitivity of fast and slow neuronal pathways.

Functional Organization of Vestibulo-Ocular Responses in Abducens Motoneurons.

Vestibulo-ocular reflexes (VORs) are the dominating contributors to gaze stabilization in all vertebrates. During horizontal head movements, abducens motoneurons form the final element of the reflex arc that integrates visuovestibular inputs into temporally precise motor commands for the lateral rectus eye muscle. Here, we studied a possible differentiation of abducens motoneurons into subtypes by evaluating their morphology, discharge properties, and synaptic pharmacology in semi-intact in vitro preparations of larval Xenopus laevis Extracellular nerve recordings during sinusoidal head motion revealed a continuum of resting rates and activation thresholds during vestibular stimulation. Differences in the sensitivity to changing stimulus frequencies and velocities allowed subdividing abducens motoneurons into two subgroups, one encoding the frequency and velocity of head motion (Group I), and the other precisely encoding angular velocity independent of stimulus frequency (Group II). Computational modeling indicated that Group II motoneurons are the major contributor to actual eye movements over the tested stimulus range. The segregation into two functional subgroups coincides with a differential activation of glutamate receptor subtypes. Vestibular excitatory inputs in Group I motoneurons are mediated predominantly by NMDA receptors and to a lesser extent by AMPA receptors, whereas an AMPA receptor-mediated excitation prevails in Group II motoneurons. Furthermore, glycinergic ipsilateral vestibular inhibitory inputs are activated during the horizontal VOR, whereas the tonic GABAergic inhibition is presumably of extravestibular origin. These findings support the presence of physiologically and pharmacologically distinct functional subgroups of extraocular motoneurons that act in concert to mediate the large dynamic range of extraocular motor commands during gaze stabilization.SIGNIFICANCE STATEMENT Outward-directed gaze-stabilizing eye movements are commanded by abducens motoneurons that combine different sensory inputs including signals from the vestibular system about ongoing head movements (vestibulo-ocular reflex). Using an amphibian model, this study investigates whether different types of abducens motoneurons exist that become active during different types of eye movements. The outcome of this study demonstrates the presence of specific motoneuronal populations with pharmacological profiles that match their response dynamics. The evolutionary conservation of the vestibulo-ocular circuitry makes it likely that a similar motoneuronal organization is also implemented in other vertebrates. Accordingly, the physiological and pharmacological understanding of specific motoneuronal contributions to eye movements might help in designing drug therapies for human eye movement dysfunctions such as abducens nerve palsy.

The same oculomotor vermal Purkinje cells encode the different kinematics of saccades and of smooth pursuit eye movements

Saccades and smooth pursuit eye movements (SPEM) are two types of goal-directed eye movements whose kinematics differ profoundly, a fact that may have contributed to the notion that the underlying cerebellar substrates are separated. However, it is suggested that some Purkinje cells (PCs) in the oculomotor vermis (OMV) of monkey cerebellum may be involved in both saccades and SPEM, a puzzling finding in view of the different kinematic demands of the two types of eye movements. Such ‘dual’ OMV PCs might be oddities with little if any functional relevance. On the other hand, they might be representatives of a generic mechanism serving as common ground for saccades and SPEM. In our present study, we found that both saccade- and SPEM-related responses of individual PCs could be predicted well by linear combinations of eye acceleration, velocity and position. The relative weights of the contributions that these three kinematic parameters made depended on the type of eye movement. Whereas in the case of saccades eye position was the most important independent variable, it was velocity in the case of SPEM. This dissociation is in accordance with standard models of saccades and SPEM control which emphasize eye position and velocity respectively as the relevant controlled state variables.

Capturing the Moment of Fusion Loss in Intermittent Exotropia

To characterize eye movements made by patients with intermittent exotropia when fusion loss occurs spontaneously and to compare them with those induced by covering 1 eye and with strategies used to recover fusion. Prospective study of a patient cohort referred to our laboratory. Thirteen patients with typical findings of intermittent exotropia who experienced frequent spontaneous loss of fusion. The position of each eye was recorded with a video eye tracker under infrared illumination while fixating on a small central near target. Eye position and peak velocity measured during spontaneous loss of fusion, shutter-induced loss of fusion, and recovery of fusion. In 10 of 13 subjects, the eye movement made after spontaneous loss of fusion was indistinguishable from that induced by covering 1 eye. It reached 90% of full amplitude in a mean of 1.75 seconds. Peak velocity of the deviating eye's movement was highly correlated for spontaneous and shutter-induced events. Peak velocity was also proportional to exotropia amplitude. Recovery of fusion was more rapid than loss of fusion, and often was accompanied by interjection of a disconjugate saccade. Loss of fusion in intermittent exotropia is not influenced by visual feedback. Excessive divergence tone may be responsible, but breakdown of alignment occurs via a unique, pathological type of eye movement that differs from a normal, physiological divergence eye movement.

Detecting Cognitive Distraction using Random Forest by Considering Eye Movement Type

Detecting distracted states can be applied to various problems such as danger prevention when driving a car. A cognitive distracted state is one example of a distracted state. It is known that eye movements express cognitive distraction. Eye movements can be classified into several types. In this paper, the authors detect a cognitive distraction using classified eye movement types when applying the Random Forest machine learning algorithm, which uses decision trees. They show the effectiveness of considering eye movement types for detecting cognitive distraction when applying Random Forest. The authors use visual experiments with still images for the detection.

A Sheep in Wolves' Clothing? Nystagmoid Eye Movements

ABSTRACTNystagmoid eye movements are involuntary eye movements that are not pure forms of nystagmus. Nystagmus, by definition, is involuntary eye movements off of fixation that are initiated by a slow phase. By contrast, nystagmoid movements are often saccades that interrupt fixation or have a fast phase followed by a slow phase. Types of nystagmoid eye movements include saccadic intrusions, such as square wave jerks and ocular flutter/opsoclonus, voluntary nystagmus, superior oblique myokymia, as well as the Heimann-Bielschowsky phenomenon. In addition, sensory intermittent exotropia is a clinical entity that should be on the differential when considering patients with involuntary eye movements, many of whom will also have a history of decreased visual acuity. Other ocular comorbidities in these patients include optic nerve and retinal pathology, as well possible neurological findings such as head trauma or demyelinating disease.

Webcam-Based Eye Movement Analysis Using CNN

Due to its low price, webcam has become one of the most promising sensors with the rapid development of computer vision. However, the accuracies of eye tracking and eye movement analysis are largely limited by the quality of the webcam videos. To solve this issue, a novel eye movement analysis model is proposed based on five eye feature points rather than a single point (such as the iris center). First, a single convolutional neural network (CNN) is trained for eye feature point detection, and five eye feature points are detected for obtaining more useful eye movement information. Subsequently, six types of original time-varying eye movement signals can be constructed by feature points of each frame, which can reduce the dependency of the iris center in low quality videos. Finally, behaviors-CNN can be trained by the time-varying eye movement signals for recognizing different eye movement patterns, which is capable of avoiding the influence of errors from the basic eye movement type detection and artificial eye movement feature construction. To validate the performance, a webcam-based visual activity data set was constructed, which contained almost 0.5 million frames collected from 38 subjects. The experimental results on this database have demonstrated that the proposed model can obtain promising results for natural and convenient eye movement-based applications.

Accuracy of eye position for saccades and smooth pursuit.

In this study, we address the question of whether a target is foveated during smooth pursuit. Specifically, we examine whether smooth pursuit eye movements land near the center-of-mass of the target, as is the case for saccades. To that end, we instructed eight untrained, healthy participants to follow moving targets, presented monocularly in a scanning laser ophthalmoscope. Stimuli moved either in a modified step-ramp (smooth pursuit), or made a single step (saccade), stepping 6° from the center. Targets were ring-shaped and either 0.6° or 1.7° in diameter. In an additional set of experiments, two participants collected more extensive data on smooth pursuit and saccades for a larger range of target sizes (0.6°, 1.7°, or 4.3°). During pursuit, eyes were rarely placed at target center, even when participants' fixational stability was taken into account. Furthermore, there was a clear tendency for distance from target center to increase with target size. This outcome was in contrast to saccades, where there was no effect of target size across participants. The difference in foveal placement between the two types of eye movements is consistent with their different purposes: closer inspection of the target for saccades versus maintenance of the target in the visual field for smooth pursuit.

OpenEyeSim: A biomechanical model for simulation of closed-loop visual perception.

We introduce OpenEyeSim, a detailed three-dimensional biomechanical model of the human extraocular eye muscles including a visualization of a virtual environment. The main purpose of OpenEyeSim is to serve as a platform for developing models of the joint learning of visual representations and eye-movement control in the perception-action cycle. The architecture and dynamic muscle properties are based on measurements of the human oculomotor system. We show that our model can reproduce different types of eye movements. Additionally, our model is able to calculate metabolic costs of eye movements. It is also able to simulate different eye disorders, such as different forms of strabismus. We propose OpenEyeSim as a platform for studying many of the complexities of oculomotor control and learning during normal and abnormal visual development.

FEATURES OF EYE MOVEMENT DISORDERS IN PATIENTS WITH CEREBELLAR LESIONS OF DIFFERENT LOCALIZATION

The review relates to modern point of view on the role of cerebellar structures in eye movement control. The review dedicates todisorders of all types of eye movements involving participating cerebellum in oculomotor and vestibular systems which are supported by experimental results. Revealing the mechanisms of eye movement disorders, especially when gaze-holding and saccadic movements, opens possibilities for its therapy.

PARALLEL ARTIFICIAL NEURAL NETWORK APPROACHES FOR DETECTING THE BEHAVIOUR OF EYE MOVEMENT USING CUDA SOFTWARE ON HETEROGENEOUS CPU-GPU SYSTEMS

Eye movement behaviour is related to human brain activation either during asleep or awake. The aim of this paper is to measure the three types of eye movement by using the data classification of electroencephalogram (EEG) signals. It will be illustrated and train using the artificial neural network (ANN) method, in which the measurement of eye movement is based on eye blinks close and open, moves to the left and right as well as eye movement upwards and downwards. The integrated of ANN with EEG digital data signals is to train the large-scale digital data and thus predict the eye movement behaviour with stress activity. Since this study is using large-scale digital data, the parallelization of integrated ANN with EEG signals has been implemented on Compute Unified Device Architecture (CUDA) supported by heterogeneous CPU-GPU systems. The real data set from eye therapy industry, IC Herbz Sdn Bhd was carried out in order to validate and simulate the eye movement behaviour. Parallel performance analyses can be captured based on execution time, speedup, efficiency, and computational complexity.

Fixating on the size-speed illusion of approaching railway trains: What we can learn from our eye movements

Railway level crossing collisions have recently been linked to a size-speed illusion where larger objects such as trains appear to move slower than smaller objects such as cars. An explanation for this illusion has centred on observer eye movements – particularly in relation to the larger, longer train. A previous study (Clark et al., 2016) found participants tend to make initial fixations to locations around the visual centroid of a moving vehicle; however individual eye movement patterns tended to be either fixation-saccade-fixation type, or smooth pursuit. It is therefore unknown as to which type of eye movement contributes to the size-speed illusion. This study isolated fixation eye movements by requiring participants to view computer animated sequences in a laboratory setting, where a static fixation square was placed in the foreground at one of two locations on a train (front and centroid). Results showed that even with the square placed around the front location of a vehicle, participants still underestimated the speed of the train relative to the car and underestimation was greater when the square was placed around the visual centroid of the train. Our results verify that manipulation of eye movement behaviour can be effective in reducing the magnitude of the size-speed illusion and propose that interventions based on this manipulation should be designed and tested for effectiveness.