Eye Movement Responses Research Articles

Feature Weighted Linguistics Classifier for Predicting Learning Difficulty Using Eye Tracking

This article presents a new approach to predict learning difficulty in applications such as e-learning using eye movement and pupil response. We have developed 12 eye response features based on psycholinguistics, contextual information processing, anticipatory behavior analysis, recurrence fixation analysis, and pupillary response. A key aspect of the proposed approach is the temporal analysis of the feature response to the same concept. Results show that variations in eye response to the same concept over time are indicative of learning difficulty. A Feature Weighted Linguistics Classifier (FWLC) was developed to predict learning difficulty in real time. The proposed approach predicts learning difficulty with an accuracy of 90%.

Vergence Eye Movements: From Basic Science to Clinical Application - Foreword to the Special Issue.

The abstract book of the last European Conference on Eye Movements [1] lists abstracts of 373 presentations, but less than five percent investigate vergence eye movements, i.e. the coordination of the right and left eye. Why then a special issue on this neglected issue? Human vision under natural conditions involves both eyes in coordination controlled by interacting processes subsumed under the concept of vergence.. Further, vergence is important for people in their daily lives since disorders of vergence can have serious consequences: ophthalmologists deal with squinting patients on the basis of heterophoria and heterotropia testing, eye strain or visual complaints can be related to impaired vergence dynamic or less accurate static vergence, remediation by optometrist includes vergence training or prism eye glasses, etc.

Holographic waveguide based optometer for the quantitative monitoring of ocular refractive error.

Oculomotor disorders are known to have profound impacts on a patients' quality of life. However, current clinical practice lacks the capability to provide simultaneous assessment of three tightly coupled oculomotor control components, i.e. eye movement, lens accommodation, and pupil response. In this study, a holographic waveguide (HW) based benchtop optometer was constructed and evaluated with a model eye. Experimental result and quantitative analysis indicate that a HW can convey high quality retinal images to a camera at an illumination level safe for human subjects and support high accuracy measurements of ocular refractive error over a wide range. Further development of a HW-based system promises a wearable, see-through device for comprehensive assessment of oculomotor control components while the subject is engaged in normal daily activities and thus enable advanced research and clinical management of oculomotor disorders.

Age Factor and its Role in the Readers’ Comprehension of Stylistic Heterogeneity: Evidence from Eye Movements and Default Responses

The article discusses the role of the age factor in the readers’ comprehension of stylistically heterogeneous texts, here the text fragments containing figurative noun groups of salient and non-salient character. The salience effects on eye movement and default responses are studied in the oculographic experiment where the secondary school children had to read the sentences displaying figurativeness. The earlier detected statistically significant corpus salience indices of referential, linguistic and discourse parameters in figurativeness construal get verified experimentally. In accordance with the Graded Salience and Defaultness hypotheses I assumed that the interpretation of figurative noun groups of varied referential, linguistic and discourse salience will require different cognitive effort in terms of both eye movement reactions and default inferences. Several eye-tracking experiments with adult participants sufficed to prove the dependency, however, the results obtained with children did not support the Salience hypothesis in the part of visual perception. The eye movements of children facing figurative noun groups did not show steady correlation patterns with the salience effects of these groups, whereas the default interpretations correlated strongly with referential, linguistic, and discourse salience. The results show evidence in favor of Mixed-Effects Model of interpretation

The Contribution of AMPA and NMDA Receptors to Persistent Firing in the Dorsolateral Prefrontal Cortex in Working Memory.

Many tasks demand that information is kept online for a few seconds before it is used to guide behavior. The information is kept in working memory as the persistent firing of neurons encoding the memorized information. The neural mechanisms responsible for persistent activity are not yet well understood. Theories attribute an important role to ionotropic glutamate receptors, and it has been suggested that NMDARs are particularly important for persistent firing because they exhibit long time constants. Ionotropic AMPARs have shorter time constants and have been suggested to play a smaller role in working memory. Here we compared the contribution of AMPARs and NMDARs to persistent firing in the dlPFC of male macaque monkeys performing a delayed saccade to a memorized spatial location. We used iontophoresis to eject small amounts of glutamate receptor antagonists, aiming to perturb, but not abolish, neuronal activity. We found that both AMPARs and NMDARs contributed to persistent activity. Blockers of the NMDARs decreased persistent firing associated with the memory of the neuron's preferred spatial location but had comparatively little effect on the representation of the antipreferred location. They therefore decreased the information conveyed by persistent firing about the memorized location. In contrast, AMPAR blockers decreased activity elicited by the memory of both the preferred and antipreferred location, with a smaller effect on the information conveyed by persistent activity. Our results provide new insights into the contribution of AMPARs and NMDARs to persistent activity during working memory tasks.SIGNIFICANCE STATEMENT Working memory enables us to hold on to information that is no longer available to the senses. It relies on the persistent activity of neurons that code for the memorized information, but the detailed mechanisms are not yet well understood. Here we investigated the role of NMDARs and AMPARs in working memory using iontophoresis of antagonists in the PFC of monkeys remembering the location of a visual stimulus for an eye movement response. AMPARs and NMDARs both contributed to persistent activity. NMDAR blockers mostly decreased persistent firing associated with the memory of the neuron's preferred spatial location, whereas AMPAR blockers caused a more general suppression. These results provide new insight into the contribution of AMPARs and NMDARs to working memory.

Intensified visual clutter induces increased sympathetic signalling, poorer postural control, and faster torsional eye movements during visual rotation

Many dizzy patients express a hypersensitivity to visual motion and clutter. This study aims to investigate how exposure to rotating visual clutter affects ocular torsion, vertical skewing, body-sway, the autonomic pupillary response, and the subjective feeling of discomfort to the stimulation. Sixteen healthy subjects were exposed to 20 seconds rotational visual stimulation (72 deg/s; 50 deg visual field). Visual stimuli were comprised of black lines on a white background, presented at low and high intensity levels of visual clutter, holding 19 lines and 38 lines respectively. Ocular torsion and vertical skewing were recorded using the Chronos Eye Tracker, which also measured pupil size as a reflection of the autonomic response. Postural control was evaluated by measuring body-sway area on the Wii Balance Board. Values were compared to data retrieved 20 seconds before and after the optokinetic stimulation, as subjects viewed the stationary visual scene. The high intensity stimulus resulted in significantly higher torsional velocities. Subjects who were exposed to low intensity first exhibited higher velocities for both intensities. Both pupil size and body sway increased for the higher intensity to both the moving and stationary visual scene, and were positively correlated to torsional velocity. In conclusion, exposure to visual clutter was reflected in the eye movement response, changes in postural control, and the autonomic response. This response may hold clinical utility when assessing patients suffering from visual motion hypersensitivity, while also providing some context as to why some healthy people feel discomfort in visually cluttered surroundings.

Target eccentricity and form influences disparity vergence eye movements responses: A temporal and dynamic analysis

This study sought to investigate whether stimulation to the fovea or the parafovea with different color combinations influenced the temporal and dynamic features of 4° disparity vergence step responses. Twelve unique types of stimuli were displayed within a haploscope presented along the participant’s midsagittal plane. Vergence eye movement responses from fifteen naïve participants were recorded using video-based infrared eye tracking instrumentation. Latency and peak velocity from left and right eye movement responses were quantified. Results show that the type of stimulus projection (foveal versus parafoveal) significantly (p<0.001) influences the vergence response latency but did not impact peak velocity. Vergence responses to eccentric circles with 6° eccentricity targeting the parafovea resulted in a significantly faster response latency compared to vergence responses to a cross with 2° eccentricity stimuli targeting the fovea. Results have implications for the stimulus design of a variety of applications from virtual reality to vision therapy interventions.

A deep convolutional neural network for automated vestibular disorder classification using VNG analysis

ABSTRACTDizziness is a frequent syndrome of peripheral vestibular lesions. Identification of nystagmus disorder can be a useful sign to discriminate between diverse vestibular diseases. Through the use of videonystagmography (VNG) device accomplished in the clinical practice of ENT department, the assessment of the rotation eye movement response supplies objective, consistent and precise measurements in the therapeutic scheme. In fact, vestibular dysfunctions introduce an important variety in their features which includes different complications for common VNG examination method. This work introduces a new scheme to reach the classification of eye movement signals from optokinetic and caloric VNG tests. The proposed method offers quantitative assessment and uniform characteristics of recurrent-included disease. The rotation angle of eye movements is classified into two classes of vestibular diseases by the use of deep convolutional Neural Network (CNN) technique. The proposed approach is validated on three different categories: a factual incorporated meniere, neurite and healthy subjects. The employed VNG dataset contain patients admitted into both Charles Nicolle and La Rabta hospitals of Tunis. Compared to previous works, the results demonstrate that the proposed CNN-based method is efficient in enhancing dizziness analysis.

Binocular 3D otolith-ocular reflexes: responses of normal chinchillas to tilt and translation.

Head rotation, translation, and tilt with respect to a gravitational field elicit reflexive eye movements that partially stabilize images of Earth-fixed objects on the retinas of humans and other vertebrates. Compared with the angular vestibulo-ocular reflex, responses to translation and tilt, collectively called the otolith-ocular reflex (OOR), are less completely characterized, typically smaller, generally disconjugate (different for the 2 eyes) and more complicated in their relationship to the natural stimuli that elicit them. We measured binocular 3-dimensional OOR responses of 6 alert normal chinchillas in darkness during whole body tilts around 16 Earth-horizontal axes and translations along 21 axes in horizontal, coronal, and sagittal planes. Ocular countertilt responses to 40-s whole body tilts about Earth-horizontal axes grew linearly with head tilt amplitude, but responses were disconjugate, with each eye's response greatest for whole body tilts about axes near the other eye's resting line of sight. OOR response magnitude during 1-Hz sinusoidal whole body translations along Earth-horizontal axes also grew with stimulus amplitude. Translational OOR responses were similarly disconjugate, with each eye's response greatest for whole body translations along its resting line of sight. Responses to Earth-horizontal translation were similar to those that would be expected for tilts that would cause a similar peak deviation of the gravitoinertial acceleration (GIA) vector with respect to the head, consistent with the "perceived tilt" model of the OOR. However, that model poorly fit responses to translations along non-Earth-horizontal axes and was insufficient to explain why responses are larger for the eye toward which the GIA vector deviates.NEW & NOTEWORTHY As the first in a pair of papers on Binocular 3D Otolith-Ocular Reflexes, this paper characterizes binocular 3D eye movements in normal chinchillas during tilts and translations. The eye movement responses were used to create a data set to fully define the normal otolith-ocular reflexes in chinchillas. This data set provides the foundation to use otolith-ocular reflexes to back-project direction and magnitude of eye movement to predict tilt axis as discussed in the companion paper.

Native Advertising in Online News: Trade-Offs Among Clicks, Brand Recognition, and Website Trustworthiness

Native advertising is a type of online advertising that matches the form and function of the platform on which it appears. In practice, the choice between display and in-feed native advertising presents brand advertisers and online news publishers with conflicting objectives. Advertisers face a trade-off between ad clicks and brand recognition, whereas publishers need to strike a balance between ad clicks and the platform’s trustworthiness. For policy makers, concerns that native advertising confuses customers prompted the U.S. Federal Trade Commission to issue guidelines for disclosing native ads. This research aims to understand how consumers respond to native ads versus display ads and to different styles of native ad disclosures, using randomized online and field experiments combining behavioral clickstream, eye movement, and survey response data. The results show that when the position of an ad on a news page is controlled for, a native ad generates a higher click-through rate because it better resembles the surrounding editorial content. However, a display ad leads to more visual attention, brand recognition, and trustworthiness for the website than a native ad.

Comparing Ocular Responses to Caloric Irrigation and Electrical Vestibular Stimulation in Vestibular Schwannoma.

Electrical Vestibular Stimulation (EVS) is a non-invasive technique for activating the vestibular-ocular reflex, evoking mainly a torsional eye movement response. We have previously demonstrated that this response can be used to detect vestibular asymmetry in patients with vestibular schwannoma (VS). Here we perform a direct comparison of EVS with caloric irrigation in this patient group. We studied 30 patients with unilateral VS, alongside an equal number of aged-matched healthy control subjects. EVS current was delivered to the mastoid process in a monaural configuration using a sinusoidal stimulus (2 Hz; ± 2 mA; 10 s), with an electrode placed over the spinous C7 process. Evoked eye movements were recorded from the right eye in darkness using an infra-red sensitive camera while the subject sat relaxed with their head on a chinrest. Ocular torsion was subsequently tracked off-line using iris striations. Each subject separately underwent water caloric irrigation, in accordance with the British Society of Audiology guidelines. For the caloric test, eye movement was recorded in the yaw axis using electro-oculography. For both EVS and calorics, inter-aural response asymmetry was calculated to determine the extent of canal paresis. Both tests revealed impaired vestibular function in the ipsilesional ear of VS patients, with a mean asymmetry ratio of 15 ± 17% and 18 ± 16% for EVS and calorics, respectively. Overall, the caloric test results discriminated controls from patients slightly more effectively than EVS (Cohen's D effect size = 1.44 vs. 1.19). Importantly, there was a significant moderate correlation between the AR values produced by EVS and calorics (r = 0.53, p < 0.01), and no significant difference between mean AR estimates. When questioned, ≥85% of participants subjectively preferred the EVS experience, in terms of comfort. Moreover, it took ~15 min to complete, vs. ~1 h for caloric. These results confirm that the results of the EVS test broadly agree with those of caloric irrigation, in terms of detecting vestibular asymmetry. Furthermore, they suggest a higher degree of convenience and patient comfort.

Responses of neurons in macaque MT to unikinetic plaids.

Response properties of MT neurons are often studied with "bikinetic" plaid stimuli, which consist of two superimposed sine wave gratings moving in different directions. Oculomotor studies using "unikinetic plaids" in which only one of the two superimposed gratings moves suggest that the eyes first move reflexively in the direction of the moving grating and only later converge on the perceived direction of the moving pattern. MT has been implicated as the source of visual signals that drives these responses. We wanted to know whether stationary gratings, which have little effect on MT cells when presented alone, would influence MT responses when paired with a moving grating. We recorded extracellularly from neurons in area MT and measured responses to stationary and moving gratings, and to their sums: bikinetic and unikinetic plaids. As expected, stationary gratings presented alone had a very modest influence on the activity of MT neurons. Responses to moving gratings and bikinetic plaids were similar to those previously reported and revealed cells selective for the motion of plaid patterns and of their components (pattern and component cells). When these neurons were probed with unikinetic plaids, pattern cells shifted their direction preferences in a way that revealed the influence of the static grating. Component cell preferences shifted little or not at all. These results support the notion that pattern-selective neurons in area MT integrate component motions that differ widely in speed, and that they do so in a way that is consistent with an intersection-of-constraints model.NEW & NOTEWORTHY Human perceptual and eye movement responses to moving gratings are influenced by adding a second, static grating to create a "unikinetic" plaid. Cells in MT do not respond to static gratings, but those gratings still influence the direction selectivity of some MT cells. The cells influenced by static gratings are those tuned for the motion of global patterns, but not those tuned only for the individual components of moving targets.

Analysis of Eye Movement and Critical Fusion Frequency Responses to Different Movie Types

Analysis of Eye Movement and Critical Fusion Frequency Responses to Different Movie Types

The "eyes have it," but when in development?: The importance of a developmental perspective in our understanding of behavioral memory formation and the hippocampus.

Lynn Nadel has been a trailblazer in memory research for decades. In just one example, Nadel and Zola-Morgan [Infantile amnesia, In Infant memory, Springer, Boston, MA, 1984, pp. 145-172] were the first to present the provocative notion that the extended development of the hippocampus may underlie the period of infantile amnesia. In this special issue of Hippocampus to honor Lynn Nadel, we review some of his major contributions to the field of memory development, with an emphasis on his observations that behavioral memory assessments follow an uneven, yet protracted developmental course. We present data emphasizing this point from memory-related eye movements [Hannula & Ranganath, Neuron, 2009, 63(5), 592-599]. Eye tracking is a sensitive behavioral measure, allowing for an indication of memory function even without overt responses, which is seemingly ideal for the investigation of memory in early childhood or in other nonverbal populations. However, the behavioral manifestation of these eye movements follows a U-shaped trajectory-and one that must be understood before these indictors could be broadly used as a marker of memory. We examine the change in preferential looking time to target stimuli in school-aged children and adults, and compare these eye movement responses to explicit recall measures. Our findings indicate change in the nature and timing of these eye movements in older children, causing us to question how 6-month-old infants may produce eye movements that initially appear to have the same properties as those measured in adulthood. We discuss these findings in the context of our current understanding of memory development, particularly the period of infantile amnesia.

Age-related differences during visual search: the role of contextual expectations and cognitive control mechanisms

ABSTRACTDuring the visual search, cognitive control mechanisms activate to inhibit distracting information and efficiently orient attention towards contextually relevant regions likely to contain the search target. Cognitive ageing is known to hinder cognitive control mechanisms, however little is known about their interplay with contextual expectations, and their role in visual search. In two eye-tracking experiments, we compared the performance of a younger and an older group of participants searching for a target object varying in semantic consistency with the search scene (e.g., a basket of bread vs. a clothes iron in a restaurant scene) after being primed with contextual information either congruent or incongruent with it (e.g., a restaurant vs. a bathroom). Primes were administered either as scenes (Experiment 1) or words (Experiment 2, which included scrambled words as neutral primes). Participants also completed two inhibition tasks (Stroop and Flanker) to assess their cognitive control. Older adults had greater difficulty than younger adults when searching for inconsistent objects, especially when primed with congruent information (Experiment 1), or a scrambled word (neutral condition, Experiment 2). When the target object violates the semantics of the search context, congruent expectations or perceptual distractors, have to be suppressed through cognitive control, as they are irrelevant to the search. In fact, higher cognitive control, especially in older participants, was associated with better target detection in these more challenging conditions, although it did not influence eye-movement responses. These results shed new light on the links between cognitive control, contextual expectations and visual attention in healthy ageing.

Virtual Rhesus Labyrinth Model Predicts Responses to Electrical Stimulation Delivered by a Vestibular Prosthesis.

To better understand the spread of prosthetic current in the inner ear and to facilitate design of electrode arrays and stimulation protocols for a vestibular implant system intended to restore sensation after loss of vestibular hair cell function, we created a model of the primate labyrinth. Because the geometry of the implanted ear is complex, accurately modeling effects of prosthetic stimuli on vestibular afferent activity required a detailed representation of labyrinthine anatomy. Model geometry was therefore generated from three-dimensional (3D) reconstructions of a normal rhesus temporal bone imaged using micro-MRI and micro-CT. For systematically varied combinations of active and return electrode location, the extracellular potential field during a biphasic current pulse was computed using finite element methods. Potential field values served as inputs to stochastic, nonlinear dynamic models for each of 2415 vestibular afferent axons, each with unique origin on the neuroepithelium and spiking dynamics based on a modified Smith and Goldberg model. We tested the model by comparing predicted and actual 3D vestibulo-ocular reflex (VOR) responses for eye rotation elicited by prosthetic stimuli. The model was individualized for each implanted animal by placing model electrodes in the standard labyrinth geometry based on CT localization of actual implanted electrodes. Eye rotation 3D axes were predicted from relative proportions of model axons excited within each of the three ampullary nerves, and predictions were compared to archival eye movement response data measured in three alert rhesus monkeys using 3D scleral coil oculography. Multiple empirically observed features emerged as properties of the model, including effects of changing active and return electrode position. The model predicts improved prosthesis performance when the reference electrode is in the labyrinth's common crus (CC) rather than outside the temporal bone, especially if the reference electrode is inserted nearly to the junction of the CC with the vestibule. Extension of the model to human anatomy should facilitate optimal design of electrode arrays for clinical application.

Vestibular Eye Movements Are Heavily Impacted by Visual Motion and Are Sensitive to Changes in Visual Intensities.

Eye movement evaluation constitutes the basis of diagnosis in dizzy patients. Through evaluating ocular torsion and vertical skewing during balance provoking stimulation, the aim of this study was to investigate the impact of vision on a typical vestibular eye movement response. Twelve healthy subjects (six young, six old) were exposed to (1) vestibular (VES), (2) visual (VIS), and (3) visual-vestibular (VIS+VES) stimulation. These were carried out as whole-body roll (VES), optokinetic rolling of visual scenes (VIS), and a combination of both (VIS+VES). Visual scenes were presented at two intensity levels. Eye movement velocities were used to evaluate the relative impact of visual and vestibular stimulation. Torsional velocities were lowest for VIS regardless of age. Velocities for the old group did not differ between VES and VIS+VES, whereas those for the young group were higher for VIS+VES. Regardless of age, amplified visual intensity resulted in an increased torsion-skewing ratio, seen as more degrees of torsion per degrees of skewing. The contributions of VIS and VES in proportion to VIS+VES were calculated as 0.18 (0.08) and 0.74 (0.14), respectively. Our findings demonstrate that vertical skewing is physiologically seen in combination with ocular torsion as a response to visual stimulation, with young subjects exhibiting a more dynamic response. The torsion-skewing ratio was sensitive to small changes in visual intensities, which may prove useful when evaluating visual motion sensitivity. The visual contribution to the vestibular eye movement response highlights the clinical importance of visual examinations when evaluating dizzy patients.

Processing speed in perceptual visual crowding.

In this study, a perceptual visual crowding paradigm was designed to quantitatively assess the detection speed of (un)crowded meaningful visual targets using eye-movement responses. This paradigm was tested in individuals with dyslexia and age-matched controls. Trials were shown on a monitor with an integrated eye tracker to 25 control and 11 dyslexic subjects without any known ocular problems. Each trial started with fixation of a central target. Next, four peripheral targets were shown (left, right, top, bottom), one being a duplicate of the central target. The duplicate was either surrounded by flankers (crowding trials) or shown in isolation (reference trials). The timing of the primary saccades were obtained as a measure for detection speed. The performance of the reference trials was significantly higher compared to the crowding trials (p < 0.05) and a 54% increase in saccadic reaction time (SRT) was found for the crowding trials. The linear mixed model revealed a significant effect of critical spacing and chart type. For the reference trials, no significant differences in SRT were found between dyslexic and control subjects. However, for the crowding trials, a significant increase of ∼13% in SRT was found in the dyslexic subjects. A first application of this paradigm showed that dyslexic subjects perform equally well in identifying visual targets in crowded as well as uncrowded scenes compared to controls. However, they seem to need more time to identify targets in crowded scenes, which might be related to the reading difficulties that they experience in general.

Decoding go/no-go decisions from eye movements.

Neural activity in brain areas involved in the planning and execution of eye movements predicts the outcome of an upcoming perceptual decision. Many real-world decisions, such as whether to swing at a baseball pitch, are accompanied by characteristic eye-movement behavior. Here we ask whether human eye-movement kinematics can sensitively predict decision outcomes in a go/no-go task requiring rapid interceptive hand movements. Observers (n = 45) viewed a moving target that passed through or missed a designated strike box. Critically, the target disappeared briefly after launch, and observers had to predict the target's trajectory, withholding a hand movement if it missed (no-go) or intercepting inside the strike box (go). We found that go/no-go decisions were reflected in distinct eye-movement responses on a trial-by-trial basis: Eye-position error and targeting-saccade dynamics predicted decision outcome with 76% accuracy across conditions. Model prediction accuracy was related to observers' decision accuracy across different levels of task difficulty and sensory-signal strength. Our findings suggest that eye movements provide a sensitive and continuous readout of internal neural decision-making processes and reflect decision-task requirements in human observers.

Velocity and Position Effects in Eye Tracking

The human visual system has distinct processing mechanisms for velocity and position information. We integrated an eye tracking device with visual stimuli to probe the distinction between the eye's response to velocity and position input. We used two types of stimuli, which we will refer to as “apparent motion” and “real motion”. Both stimuli present the viewer with wide field motion with identical Gaussian random velocity trajectories. The real motion stimulus is similar to a flipbook; we generate an initial frame with randomly distributed intensity values and shift each subsequent frame by a random drift in position. The apparent motion stimulus creates a perception of motion because successive frames are correlated in space and time. Instead of shifting each subsequent frame, we generate a library of random intensity frames, and then add each frame to a space-shifted version of the subsequent frame. Unlike the real motion stimulus, the apparent stimulus does not contain position information because there is no lasting spatial pattern across the screen. However, the eye perceives motion that it is able to track. We measured eye movement responses to both types of stimuli and calculated the coherence function between the stimulus velocity and eye velocity. Preliminary results indicate that coherence between stimulus velocity and eye velocity is similar between the two stimuli at mid-range frequencies. At high and low frequencies, coherence is stronger for the real motion stimulus. This indicates that motion perception sets in more rapidly and eye tracking lasts longer for the real stimulus that contains position information.