Journal of Eye Movement Research

11 pages, 299 KiB

Open AccessArticle

Is Poor Coordination of Saccades in Dyslexics a Consequence of Reading Difficulties? A Study Case

by Elham Ghassemi and Zoï Kapoula

J. Eye Mov. Res. 2013, 6(1), 1-11; https://doi.org/10.16910/jemr.6.1.5 - 25 Apr 2013

Cited by 3 | Viewed by 67

We hypothesize that the high quality of binocular coordination of saccades in reading is progressively learned during childhood, and this oculomotor learning is based on a synergy between saccades and vergence. In present work deficits in the binocular control of saccades in six dyslexic children (mean age was 11 ± 2.48 years) are studied for two tasks (text reading and Xs-C scanning), and at two viewing distances (40 cm and 100 cm). Fixation durations resulting are longer in Xs-C scanning task than in text reading task. We postulate that while reading motor preparation processes are executed with less demand for attentional resources. Importantly all physiological parameters of the saccades were the same for the two conditions and in either distance. Namely disconjugacy of saccades and disconjugate post-saccadic drifts were high but similar for the two conditions. Time analysis applied on saccade amplitude disconjugacy, on disconjugate post-saccadic drift and on fixation duration showed no significant effect of repetition or time. we believe that the binocular coordination deficits in dyslexic children reflect some type of microdyspraxia due to reduced oculomotor learning, perhaps related to inefficiency of the magnocellular visual system and the cerebellar functions. Full article

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13 pages, 3346 KiB

Open AccessArticle

Eye-Movements in Real Curve Driving: Pursuit-like Optokinesis in Vehicle Frame of Reference, Stability in an Allocentric-Reference Coordinate System

by Otto Lappi and Esko Lehtonen

J. Eye Mov. Res. 2013, 6(1), 1-13; https://doi.org/10.16910/jemr.6.1.4 (registering DOI) - 21 Feb 2013

Cited by 33 | Viewed by 40

Abstract

Looking at the future path and/or the tangent point (TP) have been identified as car drivers’ gaze targets in many studies on curve driving. Yet little is known in detail about these "fixations to the road". We quantitatively analyse gaze behavior at the level of individual fixations in real on-road data. We find that while gaze tracks the TP area, this pattern consists of fast optokinetic movements (smooth pursuit and fast resetting saccadic movements). Gaze is not “fixed” to the TP. We also relate eye-movements to a reference direction fixed to a point on the trajectory of the vehicle (curve exit), showing that fixations lose their pursuit-like character in this rotating system. The findings are discussed in terms of steering models and neural levels of oculomotor control. Full article

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14 pages, 2045 KiB

Open AccessArticle

Using Eye Tracking to Trace a Cognitive Process: Gaze Behaviour During Decision Making in a Natural Environment

by Kerstin Gidlöf, Annika Wallin, Richard Dewhurst and Kenneth Holmqvist

J. Eye Mov. Res. 2013, 6(1), 1-14; https://doi.org/10.16910/jemr.6.1.3 (registering DOI) - 17 Jan 2013

Cited by 74 | Viewed by 104

Abstract

The visual behaviour of consumers buying (or searching for) products in a supermarket was measured and used to analyse the stages of their decision process. Traditionally metrics used to trace decision-making processes are difficult to use in natural environments that often contain many options and unstructured information. Unlike previous attempts in this direction (i.e. Russo & Leclerc, 1994), our methodology reveals differences between a decision-making task and a search task. In particular the second (evaluation) stage of a decision task contains more re-dwells than the second stage of a comparable search task. This study addresses the growing concern of taking eye movement research from the laboratory into the ‘real-world’, so findings can be better generalised to natural situations. Full article

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24 pages, 668 KiB

Open AccessArticle

Normal Pursuit-System Limitations—First Discovered in Infantile Nystagmus Syndrome

by Louis F. Dell’Osso and Jonathan B. Jacobs

J. Eye Mov. Res. 2013, 6(1), 1-24; https://doi.org/10.16910/jemr.6.1.2 - 11 Jan 2013

Viewed by 37

Abstract

Infantile nystagmus syndrome (INS) patients occasionally have impaired pursuit. Model and patient data identified relative timing between target motion initiation and INS-waveform saccades as the cause. We used a new stimulus, the “step-pause-ramp” (SPR), to induce saccades proximal to target-velocity onset and test their effect on normal pursuit. Our OMS model predicted that proximal saccades impaired normal ramp responses, as in INS. Eye movements of subjects were calibrated monocularly and recorded binocularly; data were analyzed using OMtools software. Proximal saccades caused lengthened target acquisition times and steady-state position errors, confirming the model’s predictions. Spontaneous pursuit oscillation supported the hypothesis that INS is caused by loss of smooth-pursuit damping. Snooth pursuit may be impaired by saccades overlapping targetmotion onset. Full article

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14 pages, 765 KiB

Open AccessArticle

Localizing the Neural Substrate of Reflexive Covert Orienting

by Valerie Higenell, Brian J. White, Joshua R. Hwang and Douglas P. Munoz

J. Eye Mov. Res. 2013, 6(1), 1-14; https://doi.org/10.16910/jemr.6.1.1 (registering DOI) - 15 Dec 2012

Viewed by 59

Abstract

The capture of covert spatial attention by salient visual events influences subsequent gaze behavior. A task irrelevant stimulus (cue) can reduce (Attention capture) or prolong (Inhibition of return) saccade reaction time to a subsequent target stimulus depending on the cue-target delay. Here we investigated the mechanisms that underlie the sensory-based account of AC/IOR by manipulating the visual processing stage where the cue and target interact. In Experiment 1, liquid crystal shutter goggles were used to test whether AC/IOR occur at a monocular versus binocular processing stage (before versus after signals from both eyes converge). In Experiment 2, we tested whether visual orientation selective mechanisms are critical for AC/IOR by using oriented “Gabor” stimuli. We found that the magnitude of AC and IOR was not different between monocular and interocular viewing conditions, or between iso- and ortho-oriented cue-target interactions. The results suggest that the visual mechanisms that contribute to AC/IOR arise at an orientation-independent binocular processing stage. Full article

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J. Eye Mov. Res., Volume 6, Issue 1 (April 2013) – 5 articles

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