Search results for " Structures"
showing 10 items of 4162 documents
<title>Computerized device for critical flicker fusion frequency determination</title>
2003
The critical fusion flicker frequency of the human visual system is the threshold sensitivity for a sine wave-modulated patch of monochromatic flickering light measured as a function of its temporal frequency and average luminance level. The critical flicker fusion frequency changes in different ocular and non-ocular conditions, for example: high-myopia, AMR, glaucoma, schizophrenia, after alcohol intake, fatigue. A computerized test for critical flicker fusion frequency determination was developed. Visual stimuli are two monochromatic LED light sources that are connected to a microcircuit driven by a computer program. The control of the device is realized through the parallel port of the P…
Spectral scattering dependencies of controllable PLZT occluder for vision science applications
2001
Summary form only given. PLZT ceramics have an unique property - a facility to change the light scattering efficiency with the applied electric field. This effect is well manifested especially in the visible, just where the transparency windows of PLZT begins. Formerly we developed eye occlusion devices for vision science applications to introduce a dynamic decrease of the image contrast in stereovision tests. In future we plan to construct, using controllable scattering in PLZT, an eye simulator to study cataract caused retinal image quality reduction. The present work reports on spectral dependencies of such an eye occluder studied with the double optical integrated sphere technique.
The Development of Visuo-spatial Memory: How to Remember Location
1992
Recent studies on developmental differences in spatial memory have reported equivocal results. Some found an age-dependent improvement of memory performance whereas others did not. The two studies reported here investigate age differences in memory for visual-spatial information. A picture reconstruction task with simultaneous presentation of scene-like visual-spatial arrangements was used. Subjects had to recognise objects and to reconstruct the initial spatial arrangement. The first study with 5to 10year-olds produced the typical age-dependent improvement in recognising visual material as well as in remembering the locations of specific objects. No effect for age was obtained in memory f…
Movement Perception in the Colliculus Superior
1977
Summary Neurophysiological measurements on cats' colliculus superior show results which are dependent on the movement of visual stimuli and movement of the background as well as on the movement of stimulus and background n!lative to each other. The movement dependent problems involved in pattern recognition by space time filters as regards resolution of details, distortion and eye movement are outlined in principle.
Tuning host specificity during the ontogeny of a fish ectoparasite: behavioural responses to host-induced cues
2003
The choice between two alternative hosts, brown trout (Salmo trutta) and roach (Rutilus rutilus), and the response to visual and olfactory cues were studied in the ontogeny of Argulus coregoni. The initial preference of the smallest parasites for brighter roach changed at the age of 2 weeks, at the size of about 2 mm, for trout, a typical salmonid host. Younger argulids were attracted by a non-specific visual stimulus (white disc over dark background), and they did not respond to olfactory stimulation (fish-conditioned water). Later, the response to visual stimuli was modulated by trout-conditioned water, but not by that conditioned by roach. The primary role of vision, particularly in earl…
Verbal definitions of familiar objects in blind children reflect their peculiar perceptual experience
2012
Background The aim of the present study was to examine to what extent the verbal definitions of familiar objects produced by blind children reflect their peculiar perceptual experience and, in consequence, differ from those produced by sighted children. Methods Ninety-six visually impaired children, aged between 6 and 14 years, and 32 age-matched sighted children had to define 10 words denoting concrete animate or inanimate familiar objects. Results The blind children evoked the tactile and auditory characteristics of objects and expressed personal perceptual experiences in their definitions. The sighted children relied on visual perception, and produced more visually oriented verbalism. In…
Retinal image quality and visual stimuli processing by simulation of partial eye cataract
2016
Visual stimuli were demonstrated on a 4.3’’ mobile phone screen inside a “Virtual Reality” adapter that allowed separation of the left and right eye visual fields. Contrast of the retina image thus can be controlled by the image on the phone screen and parallel to that at appropriate geometry by the AC voltage applied to scattering PDLC cell inside the adapter. Such optical pathway separation allows to demonstrate to both eyes spatially variant images, that after visual binocular fusion acquire their characteristic indications. As visual stimuli we used grey and different color (two opponent components to vision – red-green in L*a*b* color space) spatially periodical stimuli for left and ri…
Image Content Enhancement Through Salient Regions Segmentation for People With Color Vision Deficiencies
2019
Color vision deficiencies affect visual perception of colors and, more generally, color images. Several sciences such as genetics, biology, medicine, and computer vision are involved in studying and analyzing vision deficiencies. As we know from visual saliency findings, human visual system tends to fix some specific points and regions of the image in the first seconds of observation summing up the most important and meaningful parts of the scene. In this article, we provide some studies about human visual system behavior differences between normal and color vision-deficient visual systems. We eye-tracked the human fixations in first 3 seconds of observation of color images to build real f…
How Our Gaze Reacts to Another Person’s Tears? Experimental Insights Into Eye Tracking Technology
2020
Crying is an ubiquitous human behavior through which an emotion is expressed on the face together with visible tears and constitutes a slippery riddle for researchers. To provide an answer to the question “How our gaze reacts to another person’s tears?,” we made use of eye tracking technology to study a series of visual stimuli. By presenting an illustrative example through an experimental setting specifically designed to study the “tearing effect,” the present work aims to offer methodological insight on how to use eye-tracking technology to study non-verbal cues. A sample of 30 healthy young women with normal visual acuity performed a within-subjects task in which they evaluated images of…
Visual grouping under isoluminant condition: impact of mental fatigue
2016
Instead of selecting arbitrary elements our visual perception prefers only certain grouping of information. There is ample evidence that the visual attention and perception is substantially impaired in the presence of mental fatigue. The question is how visual grouping, which can be considered a bottom-up controlled neuronal gain mechanism, is influenced. The main purpose of our study is to determine the influence of mental fatigue on visual grouping of definite information – color and configuration of stimuli in the psychophysical experiment. Individuals provided subjective data by filling in the questionnaire about their health and general feeling. The objective evidence was obtained in t…