Showing papers on "Foveal published in 1985"
TL;DR: Crowding in the fovea and peripheral vision showed that when scaled in proportion to recent estimates of the cortical magnification factor, vernier acuity is as good in the periphery as it is centrally.
638 citations
TL;DR: An improved laser interferometer allows forced choice contrast sensitivity measurements that are relatively unaffected by optical blurring in the eye; observers report a pattern resembling zebra stripes centered on the line of sight.
261 citations
TL;DR: Behavioural acuity and anatomical resolving power of the wedge-tailed eagle correspond closely and approach the highest frequency transmitted by the minimum pupil diameter of the eye and are discussed with reference to current theories of visual functioning.
205 citations
TL;DR: In a tachistoscopic dual-task study, the foveal load of a primary task was varied, and subjects were required to report the orientation of a simultaneously presented peripheral line that could occur at anyone of six retinal locations.
Abstract: In a tachistoscopic dual-task study, the foveal load of a primary task was varied, and subjects were required to report the orientation of a simultaneously presented peripheral line that could occu...
148 citations
TL;DR: The results, reported here, show that the energy detection properties of both foveal and peripheral vision are comparable, however, independently of scale, peripheral vision ignores the relative position of image components.
Abstract: Objects in peripheral vision are not simply blurred but lack quality of form. Assuming that the visual system performs a (patchwise) Fourier analysis of the retinal image (for review see ref. 2), it has been suggested that this disadvantage of peripheral vision may be due to the inability to encode properly spatial phase relationships. This is of great interest for neurological research as certain visual pathologies imply alterations of perceived form. Previous attempts at measuring phase sensitivities failed to distinguish between the detection of phase-related changes in contrast and phase coding in the visual system. We separated these processing strategies by applying the iso-second-order texture paradigm of Julesz to the discrimination of compound gratings. Our results, reported here, show that the energy detection properties of both foveal and peripheral vision are comparable, however, independently of scale, peripheral vision ignores the relative position of image components.
141 citations
TL;DR: Deaf people were more proficient in redirecting attention from one spatial location to another in the presence of irrelevant foveal information, suggesting that differences exist in the development of attentional mechanisms in deaf and hearing people.
130 citations
TL;DR: A sudden increase of activity in the prelunate gyrus of monkeys trained to execute or suppress goal-directed saccades to a peripheral target in the presence or absence of a central fixation spot is observed, which can be interpreted as a sign of the animal having directed attention to the peripheral target and/or having stopped active fixation being ready for the next goal- directed saccade without necessarily executing it.
108 citations
TL;DR: Visuotopic maps of foveal striate cortex have been obtained by means of single cell recordings from four hemispheres in two awake, behaving macaque monkeys, and were sufficiently compatible with one another that they could be combined into one.
Abstract: Visuotopic maps of foveal striate cortex have been obtained by means of single cell recordings from four hemispheres in two awake, behaving macaque monkeys. The numbers of successful separate striate penetration sites in the four hemispheres were 42, 58, 81, and 61, for a total of 242. The resolution of the maps is 10 min of visual angle, nearly an order of magnitude finer than previous maps. No striate receptive field center was found more than 5 min into the ipsilateral visual field. The four maps were sufficiently compatible with one another that they could be combined into one. There are only minor magnification differences between the right and left hemispheres and between the upper and lower quadrants. There is a vertical/horizontal magnification anisotropy of about 1.5:1 in central foveal cortex (0 to 20 min). The composite map can be approximated by the complex logarithmic equation, w = 7.7 * ln (x + iy + 0.33), where w is expressed in millimeters and x and y are expressed in degrees.
102 citations
TL;DR: Response patterns, cone input estimates, and comparison with human psychophysics suggest that two of these cell groups function as an opponent pair processing the colors red and green, and two other cell groups process the colors blue and yellow but show less well-developed opponency.
Abstract: Color-tuning curves were obtained for 218 cells in the foveal striate cortex of behaving macaques. Each cell was tested with its optimal spatial stimulus. Test colors (14 interference filters, 4 Wr...
72 citations
TL;DR: The present study incorporates eccentricity variation into this model of spatial vision by scaling the peak frequency (but not the shape) of the spatial filters with eccentricity.
58 citations
TL;DR: The bathypelagic alepocephalid teleost Bajacalifornia drakei has large eyes with sighting grooves and rostral aphakic gaps, and it is likely that new banks of rods are added to the retina, disproportionately m any in the fovea, as the fish grows.
Abstract: The bathypelagic alepocephalid teleost Bajacalifornia drakei has large eyes with sighting grooves and rostral aphakic gaps. An object in front of the fish will be imaged in both eyes through the full aperture of the lens in the temporal periphery of the retina, where a convexiclivate fovea with a prominent fovea externa is located. The fovea externa is composed of many banks of rods, up to 28 in a 39 mm specimen, compared with two banks in the peripheral retina. Estimates of foveal rod outer segments, nuclei and synaptic spherules show that there are almost twice as many outer segments as nuclei, and that the number of spherules is much fewer than either. It is likely that new banks of rods are added to the retina, disproportionately many in the fovea, as the fish grows. The paucity of synapses suggests that many rods lose contact with bipolar cells, which may make new contacts with successive banks of rods. The possible mechanism of formation of the new banks, consequences of the multiple bank arrangement, and optical function of the fovea are discussed.
TL;DR: All curve parameters, i.e. curve type, slope, X‐ and y‐intercepts were found to significantly alter with the introduction of a foveal lock, and Illumination changes did not cause significant differences in any parameter.
Journal Article•
TL;DR: It is suggested that impairment of foveal visual function due to demyelination is not more specific to fibers carrying chromatic information than to fiberscarrying luminance information.
Abstract: A psychophysical technique involving simple increment threshold measurements was used to determine foveal chromatic and luminance sensitivity in patients with multiple sclerosis (MS) and in matched normal controls. The patient group showed substantial and nonselective losses in chromatic and luminance sensitivity relative to the normal control group, and these losses were significantly correlated with each other over individual patients. It is suggested that impairment of foveal visual function due to demyelination is not more specific to fibers carrying chromatic information than to fibers carrying luminance information.
TL;DR: In this article, the ability to detect a luminance increment is lowered when there is uncertainty for its spatial location, and the frequency-of-seeing curves were generated for small foveal targets.
Abstract: In principle, the ability to detect a luminance increment is lowered when there is uncertainty for its spatial location. Frequency-of-seeing curves were generated for small foveal targets. When fixed in space the target’s detectability was more than 10 times higher than when it could occur at one of 140 locations.
TL;DR: In a study of 37 eyes, 70% demonstrated potential visual acuity at least two times better thanvisual acuity measured by conventional methods, and 20% demonstrated at least a fourfold improvement, suggesting that most patients with macular disease do not spontaneously employ their best remaining area of retina for fixation.
TL;DR: ‘critical’ areas of complete summation in the parafovea may be a better measure of functional integrity of central retina in the presence of a foveal lesion than the visual resolution that varies with the retinal area and location activated.
Abstract: Spatial contrast sensitivity functions were evaluated in 30 patients with macular disorders and 16 age-matched control subjects. Eighteen of the affected eyes had macular holes and the rest had isolated macular problems. A loss in spatial contrast sensitivity in the central visual field indicated a relative scotoma resulting from macular dysfunctions. The nature and size of a localized scotoma such as the type caused by a macular lesion was estimated by measuring spatial contrast sensitivity as a function of retinal area centered on the fovea. Such spatial-contrast-threshold perimetry was found to be helpful in differential classification of macular holes. Spatial contrast sensitivity and visual resolution improved with increasing retinal area even in the eyes with macular holes, but never reached normal sensitivity for spatial frequencies above 5 cycles per degree (cpd) within our experimental conditions. The loss in sensitivity to low spatial frequencies (⩽ 5 cpd) was found to be apparent and a function of the retinal area stimulated. The summation curves (contrast sensitivity vs. stimulus size) were abnormal for all spatial frequencies. The ‘critical’ sizes (i.e. the stimulus size above which no increase in sensitivity occurred) were always larger in the affected eyes than those in the normal. Thus ‘critical’ areas of complete summation in the parafovea may be a better measure of functional integrity of central retina in the presence of a foveal lesion than the visual resolution that varies with the retinal area and location activated. Evaluation of contrast sensitivity of the parafoveal regions with nonfunctional fovea also indicated existence of similar mechanism of spatial vision in the fovea and the parafovea.
Journal Article•
TL;DR: It is the relative inability to recover a signal from spatially correlated noise that characterizes visual discrimination in the peripheral visual field in foveal and extrafoveal vision.
Abstract: Ambiguous stimulus material was computer-generated by superimposing image components of a target-face and either a random checkerboard texture or a masking face. The recognition of the target-face was studied both for foveal and extrafoveal vision. Compensation of the peripheral disadvantage in image discrimination by rescaling the stimulus size was possible only in the case of texture. Comparable results were obtained from combining band-pass image components of the portraits. Results suggest that it is the relative inability to recover a signal from spatially correlated noise that characterizes visual discrimination in the peripheral visual field.
TL;DR: The study showed that, while theCFF may be highest at the fovea when the CFF values are generally low, stimulus parameter changes that increase the C FF result in a greater increase extra‐foveally.
TL;DR: It was found that conventional fixation disparity represents only a small, constant fraction of the misalignment through the greater portion of the vergence range, while a recently developed method based on the effect of retinal eccentricity on the width of the border enhancement band suggested that the large differences between fixation disparity are due to a fundamental, perceptual mechanism that is always at work during binocular vision.
Abstract: Conventional fixation disparity was compared with the corresponding foveal fixation misalignment measured by a recently developed method based on the effect of retinal eccentricity on the width of the border enhancement band. Unlike procedures using binocular nonius alignment, the method is not subject to adaptive changes in perceived direction. Forced convergence and divergence stimulation served as the independent variable. It was found that conventional fixation disparity represents only a small, constant fraction of the misalignment through the greater portion of the vergence range. However, when the misalignment is restricted to a small, central portion of the foveola, this relation changes drastically, and the fixation disparity can then be much larger than the fixation misalignment. During perfect fixation alignment of the foveal centers, there is always a significant amount of fixation disparity present. It is suggested that the large differences between fixation disparity and fixation misalignment are due to a fundamental, perceptual mechanism that is always at work during binocular vision, changing the relation between retinal location and perceived visual direction.
TL;DR: A general trend was seen for the negative-positive-negative (NPN) complex to extend to the contralateral channels, replacing thecontralateral positive-negative-positive (PNP) complex found with wide half-field stimulation.
Abstract: Foveal left and right half-field responses were recorded in six subjects (12 half-fields) and compared with wide half-field responses. In the foveal responses a general trend was seen for the negative-positive-negative (NPN) complex to extend to the contralateral channels, replacing the contralateral positive-negative-positive (PNP) complex found with wide half-field stimulation. Many individual variations in foveal response morphology were seen, which may be understood in terms of anatomical variation. Individual differences between foveal half-fields in the same subject may be as great as those between subjects.
TL;DR: In a recent publication, Westheimer concluded that the foveal line-separation discrimination function was smooth, but when the Westheimer data are replotted in the Weber-fraction form, segments in the discrimination function similar to those previously described by Hirsch and Hylton can be observed.
Abstract: In a recent publication, Westheimer concluded that the foveal line-separation discrimination function was smooth [ J. Opt. Soc. Am. A1, 683– 684 ( 1984)]. However, when the Westheimer data are replotted in the Weber-fraction (Δs/s) form, segments in the discrimination function similar to those previously described by Hirsch and Hylton [ J. Opt. Soc. AM.72, 1367– 1374 ( 1984)] can be observed.
TL;DR: Foveal inhibition has been studied with elementary stimuli presented at increment threshold luminance and with suprathreshold stimuli and the inhibition produced with spatially extended stimuli is described in terms of the ideas derived from measurements on elementary stimuli.
TL;DR: Foveal and peripheral nystagmus became increasingly difficult to elicit in tact with narrowing of the visual field or increase in stimulus velocity.
Abstract: The optokinetic (OK) nystagmus induced by OK stimulus on the foveal area (foveal nystagmus) or on the peripheral retina (peripheral nystagmus) are discussed. Separation of the visual field can be achieved by a combination of a projection type OK stimulator and a masking cylinder driven by a d.c. ENG. Foveal and peripheral nystagmus became increasingly difficult to elicit in tact with narrowing of the visual field or increase in stimulus velocity. The influence of velocity was much more noticeable in the foveal nystagmus. The characteristics of foveal and peripheral OK nystagmus are elucidated by the overlapping method. The foveal nystagmus has a rather distorted form, but its slow-phase eye velocity is the same as the target velocity. It has a tendency to start and reverse with slow phase. Its beating field deviates in the direction of the slow phase. The peripheral nystagmus, on the contrary, has a typical saw-tooth form and its slow-phase eye velocity is slower than the target velocity, even at the low speed stimulus. It has a tendency to start and reverse with the quick phase. Its beating field deviates in the direction of the quick phase.
TL;DR: The attentional demands of the tasks and the importance assigned to the tasks were critical factors in response speed and may help to explain the results of visual-narrowing experiments which have indicated narrowing after placing an attention-demanding task in foveal vision.
Abstract: It was hypothesized that attention could be directed to the emphasized task regardless of its spatial location. 20 subjects performed a simple RT to a stimulus located in foveal vision and a simple RT to four surrounding stimuli set in the visual periphery. Importance of task was manipulated through instructions. Analysis of variance showed subjects had shorter RTs to the emphasized area regardless of its spatial location. The attentional demands of the tasks and the importance assigned to the tasks were critical factors in response speed. This may help to explain the results of visual-narrowing experiments which have indicated narrowing after placing an attention-demanding task in foveal vision.
TL;DR: In mild optic neuropathies (with full Snellen visual acuity), contrast sensitivity to low spatial frequencies is reduced and the scatter of the threshold determination is increased and perception of desaturated colors is also reduced.
Abstract: In mild optic neuropathies (with full Snellen visual acuity), contrast sensitivity to low spatial frequencies is reduced and the scatter of the threshold determination is increased. Perception of desaturated colors is also reduced. Pattern visual evoked potentials to small checks only reveal a loss of foveal neural channels.
TL;DR: It is found that the moving radial grating preferentially raises the threshold for the low spatial frequencies of the counterphasing but not the stationary foveal stimulus, which closely parallel recent primate electrophysiological work which suggests that visual stimulation of the peripheral field with a moving radial grate can activate inhibitory corticofugal influences on lateral geniculate neurons.
TL;DR: Foveal viewing was more accurate than peripheral viewing but peripheral performance was adequately consistent as an input channel for some orientation tasks, and change in size was the weakest.
Abstract: When there is relative motion between an observer and a textured surface such as the ground, motion-related visual information is available about the orientation of the surface through vergence of the paths of the elements of the texture, change in their sizes and in their velocities. This experiment determined the perceptual effectiveness of each variable in foveal and peripheral viewing for producing perceptions of three-dimensional motion. The three variables were electronically separated and displayed singly, in all possible pairs, and all together. Subjects communicated their perceptions of degree of perceived surface tilt at the top, bottom, and middle of the display for the eight different combinations of variables because, during pilot work perceived surface bendings were frequently noted where top, bottom, and middle appeared tilted to different extents. All three variables can lead to relatively reliable perceptions of perceived orientation of the plane of motion, with change in velocity being the most powerful determiner. Change in size was the weakest. Certain combinations can lead to perceptions of extreme warping and should be avoided in motion displays. Subjects consistently underestimate the amount of simulated tilt. Foveal viewing was more accurate than peripheral viewing but peripheral performance was adequately consistent as an input channel for some orientation tasks.
TL;DR: The human fovea forms images by reflection (the foveal reflex of ophthalmoscopy) which may be used to determine its curvature “in vivo”, and in a population of young people radii of curvature lay between 1.04 and 1.7mm.
Abstract: The human fovea forms images by reflection (the foveal reflex of ophthalmoscopy) which may be used to determine its curvature “in vivo”. In a population of young people radii of curvature lay between 1.04 and 1.7mm. These values are compatible with histological data on the assumption that the foveal shape approximates a section of a sphere.
01 Jan 1985
TL;DR: In this paper, sinusoidal gratings red, green and blue (40 cd/m2) were presented to eight subjects using a psychophysical adjustment technique to establish sensitivity functions.
Abstract: Stationary sinusoidal gratings red, green and blue (40 cd/m2) were presented to eight subjects using a psychophysical adjustment technique to establish sensitivity functions; 1 — in foveal vision; 2 — in peripheral vision: 10°, 20°, 30°, 40°, nasal retina on the horizontal meridian.
01 Oct 1985
TL;DR: This article showed that an increase in foveal cognitive load can have a substantial detrimental effect on the processing of information from para-and perifoveal regions of the same display.
Abstract: The present study demonstrated that an Increase in foveal cognitive load can have a substantial detrimental effect on the processing of information from para- and perifoveal regions of the same display. Also, an instructional set which biased subjects to distribute most of their attentional resources to the foveal (primary) task resulted in much poorer performance on the parafoveal (secondary) task than an instructional set which biased subjects to allocate attentional resources over the entire display.Although reaction times on the secondary task became slower with increases in the eccentricity of the secondary task stimuli, the rate of reaction time increase was greatest for the condition that combined high foveal cognitive load with a foveal attentional bias. The results are interpreted in terms of a tunnel-vision model.