Effects of Brightness, Hue, and Saturation on Perceived Depth between Adjacent Regions in the Visual Field

Perception ◽  
1983 ◽  
Vol 12 (2) ◽  
pp. 167-175 ◽  
Author(s):  
Hiroyuki Egusa
Keyword(s):  
Visual Field ◽  
Brightness Difference ◽  
The Subject ◽  
Saturation Difference

The effects of brightness, hue, and saturation on perceived depth between adjacent regions have been examined. The stimulus consisted of two hemifields of different colors, and the subject was asked to state which appeared nearer and to judge the perceived depth between them. When both hemifields were achromatic, the perceived depth was found to increase with increasing brightness difference. Some subjects tended to judge the brighter side nearer, others the darker side nearer. With the achromatic–chromatic combination, there were no differences in perceived depth among three hue conditions, whilst with the chromatic–chromatic combination the perceived depth depended on hue combination. In terms of decreasing frequency of ‘nearer’ judgments the hue order was red, green, blue. When the two hemifields differed only in saturation, the perceived depth increased with increasing saturation difference, and whether the more saturated or the less saturated side was judged nearer depended on hue. It is argued that the effects of brightness and saturation on perceived distance from the observer can be attributed to figure–ground differentiation between adjacent regions in the visual field; but this argument does not cover the effect of hue under achromatic background conditions.

Computerized color perimetry in multiple sclerosis

1998 ◽  
Vol 4 (2) ◽  
pp. 79-84 ◽  
Author(s):  
N Accornero ◽  
S Rinalduzzi ◽  
M Capozza ◽  
E Millefiorini ◽  
G C Filligoi ◽  
...  
Keyword(s):  
Visual Field ◽  
Statistical Difference ◽  
Cost Effective ◽  
Quantitative Information ◽  
Field Analysis ◽  
Visual Field Defects ◽  
Highly Sensitive ◽  
The Subject ◽  
Color Perimetry ◽  
Field Defects

Color visual field analysis has proven highly sensitive for early visual impairments diagnosis in MS, yet it has never attained widespread popularity usually because the procedure is difficult to standardize, the devices are costly, and the test is fatiguing. We propose a computerized procedure running on standard PC, cost effective, clonable, and easy handled. Two hundred and sixty-four colored patches subtending 18 angle of vision, with selected hues and low saturation levels are sequentially and randomly displayed on gray equiluminous background of the PC screen subtending 2486408 angle of vision. The subject is requested to press a switch at the perception of the stimulus. The output provides colored maps with quantitative information. Comparison between normals and a selected population of MS patients with no actual luminance visual field defects, showed high statistical difference.

Comparison at a Distance

Perception ◽  
10.1068/p3393 ◽  
2003 ◽  
Vol 32 (4) ◽  
pp. 395-414 ◽  
Author(s):  
Marina V Danilova ◽  
John D Mollon
Keyword(s):  
Visual Field ◽  
Spatial Frequency ◽  
Visual System ◽  
Spatial Separation ◽  
Orientation Discrimination ◽  
Human Observer ◽  
Systematic Effect ◽  
Trained Subjects ◽  
Stimulus Attribute ◽  
The Subject

The visual system is known to contain hard-wired mechanisms that compare the values of a given stimulus attribute at adjacent positions in the visual field; but how are comparisons performed when the stimuli are not adjacent? We ask empirically how well a human observer can compare two stimuli that are separated in the visual field. For the stimulus attributes of spatial frequency, contrast, and orientation, we have measured discrimination thresholds as a function of the spatial separation of the discriminanda. The three attributes were studied in separate experiments, but in all cases the target stimuli were briefly presented Gabor patches. The Gabor patches lay on an imaginary circle, which was centred on the fixation point and had a radius of 5 deg of visual angle. Our psychophysical procedures were designed to ensure that the subject actively compared the two stimuli on each presentation, rather than referring just one stimulus to a stored template or criterion. For the cases of spatial frequency and contrast, there was no systematic effect of spatial separation up to 10 deg. We conclude that the subject's judgment does not depend on discontinuity detectors in the early visual system but on more central codes that represent the two stimuli individually. In the case of orientation discrimination, two naïve subjects performed as in the cases of spatial frequency and contrast; but two highly trained subjects showed a systematic increase of threshold with spatial separation, suggesting that they were exploiting a distal mechanism designed to detect the parallelism or non-parallelism of contours.

‘Skin Portraiture’ in the Age of Bio Art

2018 ◽  
Vol 24 (1-2) ◽  
pp. 137-165 ◽  
Author(s):  
Heidi Kellett
Keyword(s):  
Visual Field ◽  
Arts And Humanities ◽  
The Arts ◽  
Embodied Experiences ◽  
The Subject

In this article, I consider ‘skin portraiture’: a mode of representation that privileges quasi-anonymous, fragmented, magnified and anatomized images of skin. I argue that this mode of representation permits a heightened awareness of embodied experiences such as reflexivity, empathy and relationality. Expanding understandings of difference through its engagement with haptic imagery and visuality, skin portraiture reorients the boundaries between ‘I’/‘not I’ and subject/object – often through touch – and challenges the cultural commitment to traditional notions of bodily autonomy. By doing so, skin portraiture functions as an antagonistic form of portraiture; that is, as a kind of anti-portraiture that pushes the genre into an expanded visual field and, at times, beyond representation. Exploring the skin-as-technology metaphor, I show that bio art skin portraiture creates chimeric skins through tissue culturing practices, permitting bodies to become radically relational. Bio art skin portraits celebrate the genetic and cellular differences between bodies through a visible collapse of epidermal boundaries, which engenders a hyper-haptic mode of seeing beyond the subject and her or his skin. Analysing the bio art of Jalia Essaïdi, ORLAN and Julia Reodica, and drawing on the work of Laura Marks and Erin Manning, this article explores the skin-as-technology metaphor in order to offer the arts and humanities an innovative understanding of contemporary embodiment.

scholarly journals Noncompliance with drug therapy of glaucoma: a review about intervening factors

2009 ◽  
Vol 45 (3) ◽  
pp. 453-459 ◽  
Author(s):  
Aldemar Nemésio Brandão Vilela de Castro ◽  
Wander Araújo Mesquita
Keyword(s):  
Drug Therapy ◽  
Visual Field ◽  
Drug Treatment ◽  
Latin American ◽  
Patient Treatment ◽  
Keywords Glaucoma ◽  
Two Factors ◽  
Patient Noncompliance ◽  
The Subject ◽  
Intervening Factors

Glaucoma is defined as an optic neuropathy, characterized for loss of visual field and injury of the optic nerve, being considered as the second cause of blindness in the world, which could be prevented by the use of antiglaucoma eyedrops. The lack of adhesion of the patient to the drug treatment can culminate with loss of the vision. The objective was to revise possible literature data regarding intervening factors for noncompliance and explain estimated rates of noncompliance. A systematic review about the subject was carried out in the period of January to June of 2006. Articles had been searched in two data bases, in the National Library of Medicine (PUBMED) and in the Literature Latin American and Caribbean Health Sciences (LILACS) using the following keywords: glaucoma, compliance of the patient, noncompliance of the patient, treatment and eyedrops. In PUBMED, 199 articles were collected, written in English and French languages. No article was found in LILACS. Considering the inclusion and exclusion criteria, 27 articles were selected, with 25 originals and two reviews. Twelve possible intervening factors for noncompliance were raised, as well as estimates for rates of noncompliance. The noncompliance rates varied from 4.6% up to 59%. Two factors, forgetfulness and inadequate between-doses interval, had been associated to noncompliance of the drug therapy. The factors race, adverse effects, treatment cost, number of instilled doses, coexisting illnesses and number of eyedrops used, had resulted contradictory, being impossible to affirm that they have contributed for noncompliance. Age, sex, educational level and loss of visual field, had not been associated with noncompliance. The glaucoma patients tended to disregard the drug treatment. The wide variation in noncompliance rates could be an influence from the authors' difficulty to define the noncompliance and the variety of methodologies used to estimate it. More studies are necessary for a better evaluation of these 12 raised factors.

scholarly journals The Monocular Duke of Urbino

2016 ◽  
Vol 8s1 ◽  
pp. OED.S40918
Author(s):  
Stephen G. Schwartz ◽  
Christopher T. Leffer ◽  
Pamela S. Chavis ◽  
Faraaz Khan ◽  
Dennis Bermudez ◽  
...  
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Visual Function ◽  
Italian Renaissance ◽  
Nasal Surgery ◽  
Piero Della Francesca ◽  
Historical Figure ◽  
Eye Motion ◽  
The Subject

Federico da Montefeltro (1422–1482), the Duke of Urbino, was a well-known historical figure during the Italian Renaissance. He is the subject of a famous painting by Piero della Francesca (1416–1492), which displays the Duke from the left and highlights his oddly shaped nose. The Duke is known to have lost his right eye due to an injury sustained during a jousting tournament, which is why the painting portrays him from the left. Some historians teach that the Duke subsequently underwent nasal surgery to remove tissue from the bridge of his nose in order to expand his visual field in an attempt to compensate for the lost eye. In theory, removal of a piece of the nose may have expanded the nasal visual field, especially the “eye motion visual field” that encompasses eye movements. In addition, removing part of the nose may have reduced some of the effects of ocular parallax. Finally, shifting of the visual egocenter may have occurred, although this seems likely unrelated to the proposed nasal surgery. Whether or not the Duke actually underwent the surgery cannot be proven, but it seems unlikely that this would have substantially improved his visual function.

Residual Vision in a Subject with Damaged Visual Cortex

1999 ◽  
Vol 11 (5) ◽  
pp. 502-510 ◽  
Author(s):  
Heinz Schärli ◽  
Alison M. Harman ◽  
John H. Hogben
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Target Stimulus ◽  
Striate Cortex ◽  
Light Flash ◽  
Black And White ◽  
Confidence Levels ◽  
Residual Vision ◽  
Visual Areas ◽  
The Subject

It is well known that a lesion in the optic radiation or striate cortex leads to blind visual regions in the retinotopically corresponding portion of the visual field. However, various studies show that some subjects still perceive certain stimuli even when presented in the “blind” visual field. Such subjects either perceive stimuli abnormally or only certain aspects of them (residual vision) or, in some cases, deny perception altogether even though visual performance can be shown to be above chance (blindsight). Research on monkeys has suggested a variety of parallel extrastriate visual pathways that could bypass the striate cortex and mediate residual vision or blindsight. In the present study, we investigated a subject with perimetrically blind visual areas caused by bilateral brain damage. Black and white stimuli were presented at many locations in the intact and affected areas of the visual field. The subject's task was to state, using confidence levels, whether the target stimulus was black or white. The results revealed an area in the “blind” visual field in which the subject perceived a light flash when the experimental black stimulus was presented. We hypothesize that a spared region in the visual cortex most likely accounts for these findings.

Combined Influences of Gravitoinertial Force Level and Visual Field Pitch on Visually Perceived Eye Level

1997 ◽  
Vol 7 (5) ◽  
pp. 381-392
Author(s):  
Paul DiZio ◽  
Wenxun Li ◽  
James R. Lackner ◽  
Leonard Matin
Keyword(s):  
Visual Field ◽  
Visual Target ◽  
Weighted Average ◽  
Total Darkness ◽  
Force Level ◽  
Parallel Lines ◽  
Quantitative Characteristics ◽  
Gravitoinertial Force ◽  
The Subject ◽  
Vector Sum

Psychophysical measurements of the level at which observers set a small visual target so as to appear at eye level (VPEL) were made on 13 subjects in 1.0 g and 1.5 g environments in the Graybiel Laboratory rotating room while they viewed a pitched visual field or while in total darkness. The gravitoinertial force was parallel to the z-axis of the head and body during the measurements. The visual field consisted of two 58° high, luminous, pitched-from-vertical, bilaterally symmetric, parallel lines, viewed in otherwise total darkness. The lines were horizontally separated by 53° and presented at each of 7 angles of pitch ranging from 30° with the top of the visual field turned away from the subject (top backward) to 30° with the top turned toward the subject (top forward). At 1.5 g, VPEL changed linearly with the pitch of the 2-line stimulus and was depressed with top hackward pitch and elevated with top forward pitch as had been reported previously at 1.0 g (1.2): however, the slopes of the VPEL-vs-pitch functions at 1.0 g and 1.5 g were indistinguishable. As reported previously also (3,4), the VPEL in darkness was considerably lower at 1.5 g than at 1.0 g: however, although the y-intercept of the VPEL-vs-pitch function in the presence of the 2-line visual field (visual field erect) was also lower at 1.5 g than at 1.0 g as it was in darkness, the G-related difference was significantly attenuated by the presence of the visual field. The quantitative characteristics of the results are consistent with a model in which VPEL is treated as a consequence of an algebraic weighted average or a vector sum of visual and nonvisual influences although the two combining rules lead to fits that are equally good.

scholarly journals Inactivation of Primate Superior Colliculus Biases Target Choice for Smooth Pursuit, Saccades, and Button Press Responses

2010 ◽  
Vol 104 (3) ◽  
pp. 1538-1548 ◽  
Author(s):  
Samuel U. Nummela ◽  
Richard J. Krauzlis
Keyword(s):  
Visual Field ◽  
Superior Colliculus ◽  
Smooth Pursuit ◽  
The Other ◽  
Button Press ◽  
The Subject ◽  
Response Execution ◽  
Choice Bias ◽  
Saccade Preparation ◽  
Selection Of

In addition to its well-known role in the control of saccades, the primate superior colliculus (SC) has been implicated in the processes of target choice for overt orienting movements and for covert spatial attention. We focally inactivated the SC, by muscimol injection, while monkeys selected the target of a smooth pursuit, saccade, or button press response from two competing stimuli. The choice stimuli were placed so that one appeared within and the other appeared outside the affected visual field. SC inactivation biased the subject to choose stimuli out of the affected visual field for all three types of responses, although the effects on target choice were significantly smaller for button presses. Inactivation caused no changes in the selection of single stimuli within or out of the affected visual field, indicating the choice bias was not caused by deficits in response execution. The inactivation-induced bias for smooth pursuit and button press responses indicates SC activity is important for selecting the target, independent of any role in saccade preparation.

Blindsight Mediated by an S-Cone-independent Collicular Pathway: An fMRI Study in Hemispherectomized Subjects

2010 ◽  
Vol 22 (4) ◽  
pp. 670-682 ◽  
Author(s):  
Sandra E. Leh ◽  
Alain Ptito ◽  
Marc Schönwiesner ◽  
Mallar M. Chakravarty ◽  
Kathy T. Mullen
Keyword(s):  
Visual Field ◽  
Superior Colliculus ◽  
Control Subject ◽  
Short Wavelength ◽  
Visual Stimuli ◽  
Stimulus Presentation ◽  
Cortical Activation ◽  
Visual Hemifield ◽  
Visual Areas ◽  
The Subject

The purpose of our study was to investigate the ability to process achromatic and short-wavelength-sensitive cone (S-cone)-isolating (blue–yellow) stimuli in the blind visual field of hemispherectomized subjects and to demonstrate that blindsight is mediated by a collicular pathway that is independent of S-cone inputs. Blindsight has been described as the ability to respond to visual stimuli in the blind visual field without conscious awareness [Weiskrantz, L., Warrington, E. K., Sanders, M. D., & Marshall, J. Visual capacity in the hemianopic field following a restricted occipital ablation. Brain, 97, 709–728, 1974]. The roles of the subcortical neural structures in blindsight, such as the pulvinar and the superior colliculus, have been debated and an underlying neural correlate has yet to be confirmed. Using fMRI, we tested the ability to process visual stimuli that isolated the achromatic and short-wavelength-sensitive (S-)-cone pathways in three subjects: one control subject, one hemispherectomized subject with blindsight, and one hemispherectomized subject without blindsight. We demonstrated that (1) achromatic and S-cone-isolating stimuli presented to the normal visual hemifield of hemispherectomized subjects and to both visual hemifields of the control subject activated contralateral visual areas (V1/V2), as expected; (2) achromatic stimulus presentation but not S-cone-isolating stimulus presentation to the blind hemifield of the subject with blindsight activated visual areas FEF/V5; (3) whereas the cortical activation of the control subject was enhanced by an additional stimulus (achromatic and S-cone isolating) presented in the contralateral visual field, activation pattern of the subject with blindsight was enhanced by achromatic stimuli only. We conclude that the human superior colliculus is blind to the S-cone-isolating stimuli, and blindsight is mediated by an S-cone-independent collicular pathway.

Spatial Localization under Conflict Conditions: Is There a Single Explanation?

Perception ◽  
1979 ◽  
Vol 8 (3) ◽  
pp. 323-337 ◽  
Author(s):  
David H Warren
Keyword(s):  
Visual Field ◽  
Visual Information ◽  
Spatial Localization ◽  
Visual Dominance ◽  
Auditory Target ◽  
Proprioceptive Information ◽  
Target Information ◽  
Conflict Situations ◽  
The Subject

Visual–auditory (VA) and visual–proprioceptive (VP) localization conflict paradigms were varied to explore the comparability of the conflict situations. In experiment 1 various attempts were made to decrease the dominance of visual information over proprioceptive and auditory target information. Pairing auditory with proprioceptive information against conflicting visual information did not lessen the visual dominance, nor did dimming the visual field. A ‘cognitive’ manipulation, in which the subject was led to doubt the reliability of the visual information, reduced visual dominance over audition but not visual dominance over proprioception. This difference between the two conflict situations was further explored and corroborated in experiment 2. In experiment 3 no attempt was made to lead the subject to believe that paired discrepant targets were related, and the visual dominance of audition was strong while the visual dominance of proprioception did not occur. The apparent differences between the VA and the VP conflict situations are discussed with regard to the feasibility of generating a unitary explanation of localization conflict results. Several further factors are discussed that must be explored before undertaking such a unitary formulation.

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