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Foveal

About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.


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TL;DR: Using fMRI, this work found clear activation of formerly foveal cortex to stimuli presented at either the PRL or an isoeccentric non-PRL location in two individuals with MD, supporting the use-independent reorganization hypothesis and suggesting that reorganization is driven by passive, not use-dependent mechanisms.
Abstract: Recent work has shown that foveal cortex, deprived of its normal bottom-up input as a result of macular degeneration (MD), begins responding to stimuli presented to a peripheral retinal location. However, these studies have only presented stimuli to the “preferred retinal location,” or PRL, a spared part of the peripheral retina used by individuals with MD for fixating, face recognition, reading, and other visual tasks. Thus, previous research has not yet answered a question critical for understanding the mechanisms underlying this reorganization: Does formerly foveal cortex respond only to stimuli presented at the PRL, or does it also respond to other peripheral locations of similar eccentricity? If foveal cortex responds to stimuli at PRL because it is the long-term habitual use of this region as a functional fovea that drives the formerly foveal cortex to respond to stimuli presented at the PRL (the “use-dependent reorganization” hypothesis), then foveal cortex will not respond to stimuli presented at other locations. Alternatively, it may be that foveal cortex responds to any peripheral retinal input, independent of whether input at that retinal location has been chronically attended for months or years (the “use-independent reorganization” hypothesis). Using fMRI, we found clear activation of formerly foveal cortex to stimuli presented at either the PRL or an isoeccentric non-PRL location in two individuals with MD, supporting the use-independent reorganization hypothesis. This finding suggests that reorganization is driven by passive, not use-dependent mechanisms.

115 citations

Journal ArticleDOI
TL;DR: The results of three different experiments suggested that the relation between an object in the fovea on fixation n and an object subsequently brought into fixation n + 1 affects the time to identify the second object as discussed by the authors.
Abstract: The results of three different experiments suggested that the relation between an object in the fovea on fixation n and an object subsequently brought into the fovea on fixation n + 1 affects the time to identify the second object. In Experiment 1 we extended previous work by demonstrating that a previously seen related priming object speeded the time to name a target object even when a saccade intervened between the two objects. In Experiment 2 we replicated this result and further showed that the benefit on naming time was due to facilitation from the related object rather than inhibition from the unrelated object. In addition, naming of the target object was much slower in both experiments when there was not a peripheral preview of the target object on fixation n. However, because the effect of the foveal priming object was greater when the target was not present than when it was present, priming did not appear to make extraction of the extrafoveal information more efficient. In Experiment 3, fixation times were recorded while subjects looked at four objects in order to identify them. Fixation time on an object was shorter when a related object was fixated immediately before it, even though the four objects did not form a scene. The size of the facilitation was roughly comparable to that in several analogous experiments where scenes were used. The results suggest that the effects of a predictive scene context on object identification may be explainable in terms of an object-to-object or "intralevel" priming mechanism.

114 citations

Journal ArticleDOI
TL;DR: Monocular sensitivity to motion coherence in small field random-dot kinematograms with global leftwards or rightwards motion as a function of eccentricity along the horizontal meridian in each eye of six observers found directional isotropy was found for the superior visual field.

112 citations

Journal ArticleDOI
TL;DR: The structure of the retina is consistent, numerically, with resolution acuity at high illumination but does not account for observed changes in acuity as retinal illumination is reduced.
Abstract: The relation of the structure of the retina to factors influencing visual acuity is examined in some detail. Dimensions of the foveal cones have been redetermined in a series of measurements on histological materials from several sources. In no case has center to center distance between the most central cones in adult human eyes been found less than 2.0μ nor greater than 2.3μ, these being values for the living eye, due allowance being made for shrinkage of the preparations. Photomicrographs of the central foveal mosaic are shown to illustrate the rapid increase in center to center distance between cones a short distance from the small central fovea. These results are in general agreement with those of Polyak. This cone mosaic is in good accord with the observed effect on resolution acuity of the particular location of the image within the fovea. The central cones are of such size that the optical system of the eye at optimum pupil concentrates approximately three-quarters of the energy of a star image into a circle containing three cones, but some additional optical mechanism must exist in the retina to prevent loss of this image quality by spread of rays after the focus, but within the retinal depth represented by the length of the cones. Optical processes occurring within the cones are considered in detail. It is shown that not only is the Stiles and Crawford effect explained quantitatively by these processes, but also that the spread of rays beyond the focus is prevented, so that the retinal mosaic can behave as though the light receptors were concentrated in the focal plane. This same process also makes possible greatly increased light absorption per unit weight of cone pigment. The structure of the retina is thus consistent, numerically, with resolution acuity at high illumination but does not account for observed changes in acuity as retinal illumination is reduced. Ballistic stimulation of 10 microsecond duration eliminates effect of eye movements and serves to test both the Hecht theory of change of acuity with luminance, and the alternate hypothesis that very few quanta are absorbed per cone at threshold, statistical variation in this number accounting for the acuity change. The result of these experiments indicates that neither theory can be accepted.

112 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023144
2022385
202195
2020119
2019108
201883