scholarly journals The Influence of “Blind” Distractors on Eye Movement Trajectories in Visual Hemifield Defects

2008 ◽  
Vol 20 (11) ◽  
pp. 2025-2036 ◽  
Author(s):  
Stefan Van der Stigchel ◽  
Wieske van Zoest ◽  
Jan Theeuwes ◽  
Jason J. S. Barton
Keyword(s):  
Eye Movements ◽  
Visual Information ◽  
Striate Cortex ◽  
Optic Chiasm ◽  
Cerebral Lesions ◽  
Movement Trajectories ◽  
Visual Hemifield ◽  
Irrelevant Distractors ◽  
Retinotectal Projections ◽  
Optic Radiations

There is evidence that some visual information in blind regions may still be processed in patients with hemifield defects after cerebral lesions (“blindsight”). We tested the hypothesis that, in the absence of retinogeniculostriate processing, residual retinotectal processing may still be detected as modifications of saccades to seen targets by irrelevant distractors in the blind hemifield. Six patients were presented with distractors in the blind and intact portions of their visual field and participants were instructed to make eye movements to targets in the intact field. Eye movements were recorded to determine if blind-field distractors caused deviation in saccadic trajectories. No deviation was found in one patient with an optic chiasm lesion, which affect both retinotectal and retinogeniculostriate pathways. In five patients with lesions of the optic radiations or the striate cortex, the results were mixed, with two of the five patients showing significant deviations of saccadic trajectory away from the “blind” distractor. In a second experiment, two of the five patients were tested with the target and the distractor more closely aligned. Both patients showed a “global effect,” in that saccades deviated toward the distractor, but the effect was stronger in the patient who also showed significant trajectory deviation in the first experiment. Although our study confirms that distractor effects on saccadic trajectory can occur in patients with damage to the retinogeniculostriate visual pathway but preserved retinotectal projections, there remain questions regarding what additional factors are required for these effects to manifest themselves in a given patient.

The Saccadic System

2008 ◽  
Author(s):  
Agnes Wong
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Striate Cortex ◽  
The Body ◽  
Visual Hemifield ◽  
Tactile Stimuli ◽  
System P ◽  
Burst Neuron ◽  
Deep Layers ◽  
Orbital Position

Saccades are fast conjugate eye movements that move both eyes quickly in the same direction, so that the image of an object of interest is brought on the foveae. Saccades can be made not only toward visual targets, but also toward auditory and tactile stimuli, as well as toward memorized targets. Saccades can be generated reflexively, and they are responsible for resetting the eyes back to the mid-orbital position during vestibulo-ocular or optokinetic stimulation. Saccades need to be fast to get the eyes on the target as soon as possible. They also need to be fast because our eyes act like cameras with slow shutters—vision is so blurred during saccades that the eyes have to move quickly to minimize the time during which no clear image is captured on the foveae. Indeed, saccades are the fastest type of eye movements, and they are among the fastest movements that the body can make. Saccade speed is not under voluntary control but depends on the size of the movement, with larger saccades attaining higher peak velocities. It has been estimated that we make more than 100,000 saccades per day. The burst neuron circuits in the brainstem provide the necessary motor signals to the extraocular muscles for the generation of saccades. There is a division of labor between the pons and the midbrain, with the pons primarily involved in generating horizontal saccades and the midbrain primarily involved in generating vertical and torsional saccades. However, because eye movements are a component of cognitive and purposeful behaviors in higher mammals, the process of deciding when and where to make a saccade occurs in the cerebral cortex. Not only does the cortex exert control over saccades through direct projections to the burst neuron circuits, it also acts via the superior colliculus. The superior colliculus is located in the midbrain and consists of seven layers: three superficial layers and four intermediate/ deep layers. The three superficial layers receive direct inputs from both the retina and striate cortex, and they contain a retinotopic representation of the contralateral visual hemifield.

Eye movements in sports research and practice: Immersive technologies as optimal environments for the study of gaze behaviour

2020 ◽  
Author(s):  
David Harris ◽  
Mark Wilson ◽  
Tim Holmes ◽  
Toby de Burgh ◽  
Samuel James Vine
Keyword(s):  
Virtual Reality ◽  
Eye Movements ◽  
Eye Tracking ◽  
Visual Information ◽  
Successful Performance ◽  
Experimental Control ◽  
Research And Practice ◽  
Gaze Behaviour ◽  
Immersive Technologies

Head-mounted eye tracking has been fundamental for developing an understanding of sporting expertise, as the way in which performers sample visual information from the environment is a major determinant of successful performance. There is, however, a long running tension between the desire to study realistic, in-situ gaze behaviour and the difficulties of acquiring accurate ocular measurements in dynamic and fast-moving sporting tasks. Here, we describe how immersive technologies, such as virtual reality, offer an increasingly compelling approach for conducting eye movement research in sport. The possibility of studying gaze behaviour in representative and realistic environments, but with high levels of experimental control, could enable significant strides forward for eye tracking in sport and improve understanding of how eye movements underpin sporting skills. By providing a rationale for virtual reality as an optimal environment for eye tracking research, as well as outlining practical considerations related to hardware, software and data analysis, we hope to guide researchers and practitioners in the use of this approach.

Vision without Contours: Study of Visual Information from Ordinal Stimulation

1968 ◽  
Vol 26 (2) ◽  
pp. 335-351 ◽  
Author(s):  
Gunnar Johansson
Keyword(s):  
Eye Movements ◽  
Visual Information ◽  
Sensitivity Threshold ◽  
Continuous Change ◽  
Stimulus Motion ◽  
Pursuit Eye Movements ◽  
Illuminance Level ◽  
Sinusoidal Pattern ◽  
Moving Pattern ◽  
Sinusoidal Function

Continuous change of illuminance over retinal area in accordance with the sinusoidal function was studied as a stimulus for the human visual system. Its efficiency in controlling pursuit eye movements was compared with that of a stepwise luminance function (square wave). Such distributions of luminance were generated on a cathode ray screen (wavelength at the eye 9° and 3°) and were given a small translatory motion (2° – 12′). Ss were instructed to follow the moving pattern with pursuit eye movements. There is no difference in performance between the two types of brightness distributions. A stimulus motion of 24′ was sufficient to produce full evidence of eye tracking in all Ss also from the contour-free sinusoidal pattern. This means that the brightness change in every point of the CRT screen was far below the retinal sensitivity threshold at the illuminance level used. Thus a summation effect occurs. This was taken as a support for an hypothesis about “ordinal” stimulation. Arguments from modern neurophysiology are introduced and yield further support for the conclusion.

Eye movements in cerebral lesions

1979 ◽  
Vol 11 ◽  
pp. 30 ◽  
Author(s):  
Setsuko Takemori ◽  
Masanobu Uchigata ◽  
Makoto Ishikawa
Keyword(s):  
Eye Movements ◽  
Cerebral Lesions

scholarly journals Selection of visual information for lightness judgements by eye movements

2013 ◽  
Vol 368 (1628) ◽  
pp. 20130056 ◽  
Author(s):  
Matteo Toscani ◽  
Matteo Valsecchi ◽  
Karl R. Gegenfurtner
Keyword(s):  
Eye Movements ◽  
Visual System ◽  
Visual Information ◽  
Selection Process ◽  
Sampling Strategy ◽  
Selection Strategy ◽  
Eye Fixations ◽  
Target Layer ◽  
Highly Correlated ◽  
Selection Of

When judging the lightness of objects, the visual system has to take into account many factors such as shading, scene geometry, occlusions or transparency. The problem then is to estimate global lightness based on a number of local samples that differ in luminance. Here, we show that eye fixations play a prominent role in this selection process. We explored a special case of transparency for which the visual system separates surface reflectance from interfering conditions to generate a layered image representation. Eye movements were recorded while the observers matched the lightness of the layered stimulus. We found that observers did focus their fixations on the target layer, and this sampling strategy affected their lightness perception. The effect of image segmentation on perceived lightness was highly correlated with the fixation strategy and was strongly affected when we manipulated it using a gaze-contingent display. Finally, we disrupted the segmentation process showing that it causally drives the selection strategy. Selection through eye fixations can so serve as a simple heuristic to estimate the target reflectance.

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