Search results for "Visual Perception"
showing 10 items of 387 documents
Looking in Depth: Visual Distance Perception of Stimuli on Volumetric Multi-Planar Display
2018
Ability to distinguish relative location of visual stimuli on a multi-planar display was evaluated within psychophysical experiment in order to figure out the impact of physical distance between stimuli across depth of volumetric data.
Colour vision experimental studies in teaching of optometry
2005
Following aspects related to human colour vision are included in experimental lessons for optometry students of University of Latvia. Characteristics of coloured stimuli (emitting and reflective), determination their coordinates in different colour spaces. Objective characteristics of transmitting of colour stimuli through the optical system of eye together with various types of appliances (lenses, prisms, Fresnel prisms). Psychophysical determination of mono- and polychromatic stimuli perception taking into account physiology of eye, retinal colour photoreceptor topography and spectral sensitivity, spatial and temporal characteristics of retinal receptive fields. Ergonomics of visual perce…
Does the brain know who is at the origin of what in an imitative interaction?
2012
International audience; Brain correlates of the sense of agency have recently received increased attention. However, the explorations remain largely restricted to the study of brains in isolation. The prototypical paradigm used so far consists of manipulating visual perception of own action while asking the subject to draw a distinction between self- versus externally caused action. However, the recent definition of agency as a multifactorial phenomenon combining bottom-up and top-down processes suggests the exploration of more complex situations. Notably there is a need of accounting for the dynamics of agency in a two-body context where we often experience the double faceted question of w…
Multivariate EEG spectral analysis evidences the functional link between motor and visual cortex during integrative sensorimotor tasks
2012
The identification of the networks connecting brain areas and the understanding of their role in executing complex tasks is a crucial issue in cognitive neuroscience. In this study, specific visuomotor tasks were devised to reveal the functional network underlying the cooperation process between visual and motor regions. Electroencephalography (EEG) data were recorded from twelve healthy subjects during a combined visuomotor task, which integrated precise grip motor commands with sensory visual feedback (VM). This condition was compared with control tasks involving pure motor action (M), pure visual perception (V) and visuomotor performance without feedback (V + M). Multivariate parametric …
<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…