Visual resolution and contour interaction in the fovea and periphery

Jacobs, Robert J.

doi:10.1016/0042-6989(79)90183-4

Cited by 178 publications

(128 citation statements)

References 19 publications

Supporting

Mentioning

117

Contrasting

Unclassified

Order By: Relevance

“…When flanking elements are complex, e.g., letters, spatial impairment may be considered as crowding. Classical contour interaction is observed in both normal and amblyopic foveae (Flom et al, 1963;Hess & Jacobs, 1979;Levi et al, 2002a, Hess et al, 2000, 2001, and at different retinal eccentricities where like crowding, the effect is greater than at the fovea (Jacobs, 1979;Wolford & Chambers, 1984;Hess, Dakin, Kapoor & Tewfik, 2000a). The underlying mechanisms of contour interaction and crowding in foveal vision have recently been debated (e.g.…”

Section: Introductionmentioning

confidence: 99%

Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs

2013

View full text Add to dashboard Cite

Contrast-modulated (CM) stimuli are processed by spatial mechanisms that operate at larger spatial scales than those processing luminance-modulated (LM) stimuli and may be more prone to deficits in developing, amblyopic, and aging visual systems. Understanding neural mechanisms of contour interaction or crowding will help in detecting disorders of spatial vision. In this study, contour interaction effects on visual acuity for LM and CM C and bar stimuli are assessed in normal foveal vision. In Experiment 1, visual acuity is measured for all-LM and all-CM stimuli, at ∼3.5× above their respective modulation thresholds. In Experiment 2, visual acuity is measured for Cs and bars of different type (LM C with CM bars and vice versa). Visual acuity is degraded for CM compared with LM Cs (0.46 ± 0.04 logMAR vs. 0.18 ± 0.04 logMAR). With nearby bars, CM acuity is degraded further (0.23 ± 0.01 logMAR or ∼2 lines on an acuity chart), significantly more than LM acuity (0.11 ± 0.01 logMAR, ∼1 line). Contour interaction for CM stimuli extends over greater distances (arcmin) than it does for LM stimuli, but extents are similar with respect to acuities (∼3.5× the C gap width). Contour interaction is evident when the Cs and bars are defined differently: it is stronger when an LM C is flanked by CM bars (0.17 ± 0.03 logMAR) than when a CM C is flanked by LM bars (0.08 ± 0.02 logMAR). Our results suggest that contour interaction for foveally viewed acuity stimuli involves feature integration, such that the outputs of receptive fields representing Cs and bars are combined. Contour interaction operates at LM and CM representational stages, it can occur across stage, and it is enhanced at the CM stage. Greater contour interaction for CM Cs and bars could hold value for visual acuity testing and earlier diagnosis of conditions for which crowding is important, such as in amblyopia.

show abstract

Section: Introductionmentioning

confidence: 99%

Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs

2013

View full text Add to dashboard Cite

show abstract

“…First, there is a decrease of visual acuity outside the centre of fixation. It has been shown [ 1, 2,32,42] that the resolution of the visual system decreases rapidly for stimuli presented outside the fixation location, and certainly when these stimuli are flanked by other stimuli (i.e., the phenomenon of lateral masking or inhibition [6]). This is even true for distances less than one degree; that is, for stimuli well within the foveal area.…”

Section: Processing Foveally Presented Wordsmentioning

confidence: 99%

Interhemispheric transfer and the processing of foveally presented stimuli

Brysbaert

1994

Behavioural Brain Research

123

169

View full text Add to dashboard Cite

Two arguments are commonly given in favor of a nasotemporal overlap along the vertical meridian of the visual field: anatomical findings and the existence of macular sparing in hemianopia. A review of the literature, however, points to the weakness of the evidence. The anatomical indications are exclusively based on horseradish peroxidase studies, which can not give an unequivocal answer to the amount of overlap in central vision, and which were not supported by a recent study that made use of the more direct ["C]2deoxy-D-glucose technique. The argument of macular sparing in hemianopia appears to be derived evidence that depends on the validity of the anatomical findings. In addition, behavioral studies consistently failed to find functional confirmation of the overlap. To further test the possibility of bilateral representation in central vision, a new paradigm is proposed. It is argued that if interhemispheric transfer is needed for the processing of foveally presented stimuli, the word-beginning superiority effect should be larger for subjects with left hemisphere dominance than for subjects with right hemisphere dominance. Results are in line with the hypothesis and point to the fact that interhemispheric transfer of visual information may be involved in more processing than usually accepted. It is also noted that transfer time seems to depend on the amount of information that must be transferred, and is significantly shorter than the estimates obtained in visual half field studies.Key words: Corpus callosum; Interhemispheric transfer; Macular sparing; Foveal vision; Optimal viewing position; Visual half field studies vision in the foveal region, a phenomenon called macular or foveal sparing. I will discuss the two arguments successively. Anatomical evidence of a hemiretinal overlapThe anatomical evidence for an overlap between the nasal and the temporal hemiretina comes from studies of unilateral sectioning of the optic tract or unilateral electrophoretic injection of horseradish peroxidase (HRP) into the dorsal lateral geniculate nucleus (dLGN) [ 19,20,35,36,52,53,55]. This technique allows tracing the ganglion cells of the retina which project to the dLGN and from there to the visual cortex. The general finding is that in a strip of about 0.2 mm along the vertical midline, ipsilaterally and contralaterally projecting ganglion cells intermingle. This is true both for cats and monkeys. According to Leventhal et al. [35,36] the overlap is primarily due to the presence of ipsilaterally projecting cells in the nasal hemiretina, rather than to contralaterally projecting cells in the temporal hemiretina. Interhemispheric transfer and the processing of foveally presented stimuliDue to the partial decussation of the optic nerves at the optic chiasm, the human visual field is split in two halves: the left and the right visual field (LVF and RVF). Both hemifields project to the contralateral cerebral hemisphere. That is, stimuli presented in the LVF are transmitted to the right cerebral hemisphere, and stimu...

show abstract

“…It shows the amount of information available from individual letters in a seven-letter word, and from the total word, based on the assumptions that the amount of information from the directly fixated letter has the value of 1, and that there is a drop of .1 (an arbitrarily chosen value) in information for each letter position unit of distance from that location. Jacobs (1979) estimates the rate of increase in the minimal angle of resolution, as a function of retinal eccentricity, to be .61 min of arc for each degree increase in eccentricity, for laterally masked letters. Given these assumed parameters, word identification failure is lowest with the eyes at the center of the word (e.g., total visual information is greatest with the eyes at that point), and the function relating fixation location to total visual information from a word is a parabola.…”

Section: Refi Xati Ons On Words -6mentioning

confidence: 99%

Eye movement control during reading: II. Frequency of refixating a word

McConkie

Kerr

Reddix

et al. 1989

Perception & Psychophysics

215

170

View full text Add to dashboard Cite

An analysis of over 40,000 eye fixations made by college students during reading indicates that the frequency of immediately refixating a word following an initial eye fixation on it varies with the location of that fixation. The refixation frequency is lowest near the center of the word and positively accelerating with distance from the center. The data are well fit by a parabolic function. Assuming that refixation frequency is related to the frequency of successful word identification, the observed curvilinear relation results naturally from models that postulate a linear decrease in acuity with retinal eccentricity. A single letter difference in fixation location in a word can make a sizeable difference in the likelihood of refixating that word. The effects of word length and cultural frequency on the frequency of refixating are also examined.McConkie, Kerr, Reddix, Zola, & Jacobs EYE MOVEMENT CONTROL DURING READING: II. FREQUENCY OF REFIXATING A WORDDuring reading, people fixate more frequently near the centers of words than near the beginnings and ends (Rayner, 1979). O'Regan (1981) proposed a Convenient Viewing Position hypothesis, stating that readers learn to send their eyes to the centers of words because, across the words in a language, that location is optimal for word identification. Due to the rapid drop in visual acuity with distance from the center of the fovea, together with the fact that letters bounded by spaces are more perceptible (Bouma, 1978;Jacobs, 1987), the letters of a word are maximally identifiable when the eyes are near the word's center. O'Regan further suggested that the further the eyes lie from the Convenient Viewing Position, the greater the probability that a second eye fixation on the word will be required for identification. This prediction was confirmed in a word identification study (O'Regan, 1984), which found that the frequency of making a second fixation on a word is minimized when the initial fixation is near the center of that word. Furthermore, the frequency of refixating increases as the distance of the first fixation from the center of the word increases. We refer to this relationship as the Word Refixation Frequency Curve, or simply as the word refixation curve. The existence of a word refixation curve in word identification tasks has been replicated (O'Regan, Levy-Schoen, Pynte, & Brugaillere, 1984) and there is some evidence that it may also be present in the eye fixation pattern made during reading (Blanchard & McConkie, cited by O'Regan & Levy-Schoen, 1987).

show abstract

Visual resolution and contour interaction in the fovea and periphery

Cited by 178 publications

References 19 publications

Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs

Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs

Interhemispheric transfer and the processing of foveally presented stimuli

Eye movement control during reading: II. Frequency of refixating a word

Contact Info

Product

Resources

About