Saccadic eye movements of dyslexic adult subjects

doi:10.1016/0028-3932(93)90146-Q

Neuropsychologia

Volume 31, Issue 9, September 1993, Pages 887-906

https://doi.org/10.1016/0028-3932(93)90146-Q Get rights and content

Abstract

The characteristics of visually guided saccadic eye movements were compared in 12 normal adult subjects and 12 test subjects of normal intelligence, but with problems in reading and writing. All subjects were examined psychometrically for different cognitive abilities, and for their reading and writing capabilities. The anamnestic reports about their reading and writing problems earlier in their lives were analysed. Based on scores of the writing and reading tests, the test group was subdivided into two subgroups: A and B (group A reached medium, group B very low scores in both tests). Five different non-cognitive eye movement tasks were applied: two single tasks (gap and overlap) requiring single saccades from a fixation point to a peripherally appearing target and three sequential tasks (overlap, synchronous, and simultaneous) requiring sequences of saccades to four equally spaced targets presented sequentially to the right side from an initial fixation point. Many parameters of the subjects' eye movement performance were determined and their mean values were calculated for each subject. The Student t-test revealed that the eye movement data of the two test groups deviated differently from the data of the control group. Group B had the largest deviation of the eye movement parameter from the control group. The differentiating parameters were the consistency of target acquisition, the saccadic reaction time, and the number of anticipatory responses in the single target tasks. In the sequential tasks these differences were in the amplitude, the number of saccades, and the fixation durations. The incidence of regressive saccades did not discriminate between test subjects and controls. The possible underlying deficits in the attentional control over the saccadic system and their implications for reading are discussed.

References (34)

D. Adler-Grinberg et al.
Eye movements, scanpaths, and dyslexia
Am. J. Optom. Physiol. Optics
(1978)
M. Biscaldi et al.
Saccadic eye movements of dyslexic children in non-cognitive tasks
J.R. Brannan et al.
Allocation of visual attention in good and poor readers
Percept. Psychophys.
(1987)
D. Braun et al.
Saccadic reaction times in patients with frontal and parietal lesions
Brain
(1993)
R. Brickenkamp
Test d2
B. Brown et al.
Predictive eye movements do not discriminate between dyslexic and control children
Neuropsychologia
(1983)
G.J. Brutten et al.
Eye movements of stuttering and nonstuttering children during silent reading
J. Speech Hear. Res.
(1984)
D.R. Dossetor et al.
Dyslexia and eye movements
Lang. Speech
(1975)
B. Fischer
The preparation of visually guided saccades
Rev. Physiol. Biochem. Pharmacol.
(1987)
B. Fischer et al.
Saccadic eye movements after extremely short reaction times in the monkey
Brain Res.
(1983)

B. Fischer et al.

Cerebral cortex

B. Fischer et al.

Mechanisms of visual attention revealed by saccadic eye movements

Neuropsychologia

(1987)

B. Fischer et al.

Human express saccades: Extremely short reaction times of goal directed eye movements

Exp. Brain Res.

(1984)

B. Fischer et al.

Saccadic reaction times of dyslexic and age-matched normal subjects

Perception

(1990)

B. Fischer et al.

Separate populations of visually guided saccades in humans: Reaction times and amplitudes

Exp. Brain Res.

(1992)

A.W. Inhoff et al.

Covert attention and eye movements during reading

Q. J. exp. Psychol.

(1989)

R.P. Kalesnykas et al.

The differentiation of visually guided and anticipatory saccades in gap and overlap paradigms

Exp. Brain Res.

(1987)

Cited by (57)

Predictive Model for Dyslexia from Fixations and Saccadic Eye Movement Events
2020, Computer Methods and Programs in Biomedicine
Citation Excerpt :
The number of saccades and the fixation durations are observed to be different in dyslexics. Saccades were less in number and fixation time was more for dyslexics compared to non-dyslexics [24]. This work proposed a statistical model for the prediction of dyslexia using eye movements.
Dyslexia is a disorder characterized by difficulty in reading such as poor speech and sound recognition. They have less capability to relate letters and form words and exhibit poor reading comprehension. Eye-tracking methodologies play a major role in analyzing human cognitive processing. Dyslexia is not a visual impairment disorder but it's a difficulty in phonological processing and word decoding. These difficulties are reflected in their eye movement patterns during reading.
The disruptive eye movement helps us to use eye-tracking methodologies for identifying dyslexics.
In this paper, a small set of eye movement features have been proposed that contribute more to distinguish between dyslexics and non-dyslexics by machine learning models. Features related to eye movement events such as fixations and saccades are detected using statistical measures, dispersion threshold identification (I-DT) and velocity threshold identification (I-VT) algorithms. These features were further analyzed using various machine learning algorithms such as Particle Swarm Optimization (PSO) based SVM Hybrid Kernel (Hybrid SVM – PSO), Support Vector Machine (SVM), Random Forest classifier (RF), Logistic Regression (LR) and K-Nearest Neighbor (KNN) for classification of dyslexics and non-dyslexics.
The accuracy achieved using the Hybrid SVM –PSO model is 95.6 %. The best set of features that gave high accuracy are average no of fixations, average fixation gaze duration, average saccadic movement duration, total number of saccadic movements, and average number of fixations.
It is observed that eye movement features detected using velocity-based algorithms performed better than those detected by dispersion-based algorithms and statistical measures.
Reading deficits in schizophrenia and their relationship to developmental dyslexia: A review
2018, Schizophrenia Research
Citation Excerpt :
Quantitative studies have also found deficits, with replicable findings of reduced gain and elevated saccade rates (e.g., Black et al., 1984; Eden et al., 1994; Fukushima et al., 2005; Judge et al., 2006; Lennerstrand et al., 1993; Masters, 1988; Sucher and Stewart, 1993; cf. Brown et al., 1983a, 1983b; Yang et al., 2010). Reflexive saccade studies have been equivocal, with some studies reporting longer latencies (Bucci et al., 2008; Dossetor and Papaioannou, 1975; Fischer and Weber, 1990; Pirozzolo and Rayner, 1978), others reporting shorter latencies and more express saccades (Bednarek et al., 2006; Biscaldi et al., 1994; Fischer et al., 1993), and yet others reporting no differences (Adler-Grinberg and Stark, 1978; Black et al., 1984; Brown et al., 1983a, 1983b; Leisman et al., 1978; Stanley et al., 1983). Two studies reported hypometric saccades in a predictive saccade task (Elterman et al., 1980; Pavlidis, 1981), but others found no differences (Brown et al., 1983a, 1983b; Olson et al., 1983).
Although schizophrenia and developmental dyslexia are considered distinct disorders in terms of clinical presentation and functional outcome, they both involve disruption in the processes that support skilled reading, including language, auditory perception, visual perception, oculomotor control, and executive function. Further, recent work has proposed a common neurodevelopmental basis for the two disorders, as suggested by genetic and pathophysiological overlap. Thus, these lines of research suggest that reading may be similarly impacted in schizophrenia and dyslexia. In this review, we survey research on reading abilities in individuals with schizophrenia, and review the potential mechanisms underlying reading deficits in schizophrenia that may be shared with those implicated in dyslexia. Elucidating the relationship between reading impairment in schizophrenia and dyslexia could allow for a better understanding of the pathophysiological underpinnings of schizophrenia, and could facilitate remediation of cognitive deficits that impact day-to-day functioning.
Rapid and persistent adaptability of human oculomotor control in response to simulated central vision loss
2013, Current Biology
Citation Excerpt :
Gaze position data were first preprocessed by an edge-preserving median filter with a 200 ms window in order to remove transient noise. Then, a modified version of a standard parsing algorithm [38, 39] was applied to the preprocessed data in order to robustly classify saccades and fixations while excluding microsaccades [40]. We defined a period of eye movement as a saccade if the following conditions were met: (1) the eye velocity exceeded 20° per s during the entire period, (2) the peak velocity during this period was in the top 25th percentile of the recording phase, (3) the beginning and end of this period had a velocity of at least 15% of the peak velocity, and (4) the amplitude of the eye movement during this period exceeded 0.9°.
The central region of the human retina, the fovea, provides high-acuity vision. The oculomotor system continually brings targets of interest into the fovea via ballistic eye movements (saccades). Thus, the fovea serves both as the locus for fixations and as the oculomotor reference for saccades. This highly automated process of foveation is functionally critical to vision and is observed from infancy [1, 2]. How would the oculomotor system adjust to a loss of foveal vision (central scotoma)? Clinical observations of patients with central vision loss [3, 4] suggest a lengthy adjustment period [5], but the nature and dynamics of this adjustment remain unclear. Here, we demonstrate that the oculomotor system can spontaneously and rapidly adopt a peripheral locus for fixation and can rereference saccades to this locus in normally sighted individuals whose central vision is blocked by an artificial scotoma. Once developed, the fixation locus is retained over weeks in the absence of the simulated scotoma. Our data reveal a basic guiding principle of the oculomotor system that prefers control simplicity over optimality. We demonstrate the importance of a visible scotoma on the speed of the adjustment and suggest a possible rehabilitation regimen for patients with central vision loss.
Evaluating the human ongoing visual search performance by eye tracking application and sequencing tests
2012, Computer Methods and Programs in Biomedicine
Citation Excerpt :
The minimum duration of fixation was set at the standard 100 ms, the maximum dispersion to identify fixations was at 1°. Saccades (Fig. 1) were calculated by a two step procedure [28]: firstly, the algorithm looked for data points with velocity exceeding the maximum speed limit (30°/s [29]) and, then, identified the maximum velocity over contiguous points assigning these points to the same saccade. The saccade was identified by its velocity, the time duration and the start and the end points.
Human visual search is an everyday activity that enables humans to explore the real world. Given the visual input, during a visual search, it is necessary to select some aspects of input to shift the gaze to next target. The aim of the study is to develop a mathematical method able to evaluate the visual selection process during the execution of a high cognitively demanding task such as the trial making test part B (TMT). The TMT is a neuro-psychological instrument where numbers and letters should be connected to each other in numeric and alphabetic order. We adapted the TMT to an eye-tracking version, and we used a vector model, the “eight pointed star” (8PS), to discover how selection (fixations) guides next exploration (saccades) and how human top-down factors interact with bottom-up saliency. The results reported a trend to move away from the last fixations correlated to the number of distracters and the execution performance.
Evaluating gaze control on a multi-target sequencing task: The distribution of fixations is evidence of exploration optimisation
2012, Computers in Biology and Medicine
Many high cognitive applications, such as vision processing and representation and understanding of images, often need to analyse in detail how an ongoing visual search was performed in a representative subset of the image, which may be arranged into sequences of loci, called regions of interest (ROIs). We used the Trial Making Test (TMT) in which subjects are asked to fixate a sequence of letters and numbers in a logical alphanumeric order. The main characteristic of TMT is to force the subject to perform a default and well-known path. The comparison of the expected scan-path with the observed scan-path provides a valuable method to investigate how a task force the subject to maintain a top-down internal representation of execution and how bottom-up influences the performance. We developed a mechanism that analyses the scan path using different algorithms, and we compared it with other methods: we found that fixations outside the ROI are direct influence of exploration strategy. The paper discusses the method in healthy subjects.
Spike removal through multiscale wavelet and entropy analysis of ocular motor noise: A case study in patients with cerebellar disease
2011, Journal of Neuroscience Methods
Citation Excerpt :
In particular, we propose a method to remove signal artefacts such as spikes. Spikes are unwanted and uninteresting rapid signal artifacts (Juhola et al., 1987) that may deceive pattern recognition algorithms and be confused with saccades (Fig. 3; see Fischer and Biscaldi, 1993 for the most common algorithm of saccades), or induce the fixation search algorithm to over-segmentate (Salvucci and Goldberg, 2000; Veneri et al., 2010b). Techniques based on linear or adaptive filters, or spectrum analysis may affect the morphological characteristics of gaze noise.
Wavelet decomposition of ocular motor signals was investigated with a view to its use for noise analysis and filtering. Ocular motor noise may be physiological, depending on brain activities, or experimental, depending on the eye recording machine, head movements and blinks. Experimental noise, such as spikes, must be removed, preserving noise due to neuro-physiological activities. The proposed method uses wavelet multiscale decomposition to remove spikes and optimizes the procedure by means of the covariance of the eye signals. To measure the noise on eye motor control, we used the wavelet entropy. The method was tested on patients with cerebellar disorders and healthy subjects. A significant difference in wavelet entropy was observed, indicating this quantity as a valuable measure of physiological motor noise.

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Saccadic eye movements of dyslexic adult subjects

Abstract

Eye movements, scanpaths, and dyslexia

Am. J. Optom. Physiol. Optics

Saccadic eye movements of dyslexic children in non-cognitive tasks

Allocation of visual attention in good and poor readers

Percept. Psychophys.

Saccadic reaction times in patients with frontal and parietal lesions

Brain

Test d2

Predictive eye movements do not discriminate between dyslexic and control children

Neuropsychologia

Eye movements of stuttering and nonstuttering children during silent reading

J. Speech Hear. Res.

Dyslexia and eye movements

Lang. Speech

The preparation of visually guided saccades

Rev. Physiol. Biochem. Pharmacol.

Saccadic eye movements after extremely short reaction times in the monkey

Brain Res.

Cerebral cortex

Mechanisms of visual attention revealed by saccadic eye movements

Neuropsychologia

Human express saccades: Extremely short reaction times of goal directed eye movements

Exp. Brain Res.

Saccadic reaction times of dyslexic and age-matched normal subjects

Perception

Separate populations of visually guided saccades in humans: Reaction times and amplitudes

Exp. Brain Res.

Covert attention and eye movements during reading

Q. J. exp. Psychol.

The differentiation of visually guided and anticipatory saccades in gap and overlap paradigms

Exp. Brain Res.