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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: An absence of bilateral superposition of the binocular fields, wither direct or postsynaptically, was noted at the tectal level, in spite of occasionally observed binocular fixation movements of the eyes, which probably makes possible an independent functioning of monocular fixation mechanisms in these predatory teleosts.
49 citations
TL;DR: It is concluded that, even in a heterogeneous population, abnormal early visual experience commonly leads to regionally specific cortical adaptations.
Abstract: Amblyopia is a developmental visual disorder associated with loss of monocular acuity and sensitivity as well as profound alterations in binocular integration Abnormal connections in visual cortex are known to underlie this loss, but the extent to which these abnormalities are regionally or retinotopically specific has not been fully determined This functional magnetic resonance imaging (fMRI) study compared the retinotopic maps in visual cortex produced by each individual eye in 19 adults (7 esotropic strabismics, 6 anisometropes and 6 controls) In our standard viewing condition, the non-tested eye viewed a dichoptic homogeneous mid-level grey stimulus, thereby permitting some degree of binocular interaction Regions-of-interest analysis was performed for extrafoveal V1, extrafoveal V2 and the foveal representation at the occipital pole In general, the blood oxygenation level-dependent (BOLD) signal was reduced for the amblyopic eye At the occipital pole, population receptive fields were shifted to represent more parafoveal locations for the amblyopic eye, compared with the fellow eye, in some subjects Interestingly, occluding the fellow eye caused an expanded foveal representation for the amblyopic eye in one early–onset strabismic subject with binocular suppression, indicating real-time cortical remapping In addition, a few subjects actually showed increased activity in parietal and temporal cortex when viewing with the amblyopic eye We conclude that, even in a heterogeneous population, abnormal early visual experience commonly leads to regionally specific cortical adaptations
49 citations
17 Jun 2013
TL;DR: The debut demonstration of the blind spot in the visual field is comparably surprising and indicates the existence of the perceptual blind spot is owed to the specific architecture of the retina.
Abstract: It comes as a surprise to discover that the foveal area in which one has
high resolution and high acuity vision is minute; it encompasses a mere
2° of visual angle-roughly, the area of the thumbnail at arm's length.
The introspective guess concerning acuity in depth likewise errs on the
side of extravagance; the region of crisp, fused perception is, at arm's
length, only a few centimeters deep; closer in, the area of fused
perception is even narrower. The eyes make a small movement-a
saccade-about every 200-300 milliseconds, sampling the scene by
shifting continuously the location of the fovea. Presumably
interpolation across intervals of time to yield an integrated spatiotemporal representation is a major component of what brains do.
Interpolation in perception probably enables generation of an internal
representation of the world that is useful in the animal's struggle for
survival.
49 citations
TL;DR: Analysis of event-related brain potentials and performance measures suggest that the N160 reflects the distribution of attention to different spatial locations within a task while the N190 may index the Distribution of general purpose perceptual resources.
Abstract: The effects of foveal task difficulty on the processing of events in the visual periphery were investigated through an analysis of event-related brain potentials and performance measures. Subjects performed a foveally presented continuous monitoring task both separately and together with an arrow discrimination task that was presented at three different retinal eccentricities. The subjects detected occasional failures in the monitoring task while also responding to designated targets in the left and right visual fields. The analysis of the event-related brain potentials elicited by discrete events in the arrow discrimination task indicated that the amplitude of the N190 and P300 components decreased with both the introduction of the foveal task and an increase in its difficulty. The N160 component was sensitive to the distribution of attention within a task but was uninfluenced by dual task demands. These findings suggest that the N160 reflects the distribution of attention to different spatial locations within a task while the N190 may index the distribution of general purpose perceptual resources. P300 appears to index the allocation of perceptual/central processing resources. The implications of the results for models of resource allocation and attentional gradients are discussed.
49 citations
TL;DR: A limited change in visual acuity was observed in a cohort of 38 patients with XLRS even over an extended period, however, those patients with non–cystic-appearing changes within the fovea, including pigment mottling or an atrophic-appearance lesion, tended to have a more appreciable degree of visual acute impairment compared with those patientswith a cystic- appearing foveal change.
Abstract: Purpose To determine the presence of fundus findings and natural course of visual acuity change in patients with juvenile X-linked retinoschisis (XLRS). Methods A retrospective longitudinal study of 38 patients with juvenile XLRS (age range, 9-65 years) was conducted. Best-corrected visual acuity, Goldmann visual fields, and results of slit-lamp biomicroscopy of the anterior segment and dilated fundus examination were obtained for all patients. Visual acuity findings at the most recent and initial visits were compared. Follow-up ranged from 1 year to 28 years (mean, 10.2 years). Twenty-five patients were observed for > 5 years, and 11, for > or = 15 years. Results Foveal lesions varied from predominantly radial striations (3%), microcystic lesions (34%), honeycomblike cysts (8%), or their combinations (31%) to non-cystic-appearing foveal changes, such as pigment mottling (8%), loss of the foveal reflex (8%), or an atrophic-appearing lesion (8%). Twelve patients (32%) had situs inversus of their retinal vessels. We observed a superior nasal restriction in the peripheral visual field even in the absence of clinically apparent peripheral retinoschisis. Of the 38 patients who were seen more than once, using logarithm of the minimum angle of resolution (logMAR) comparison, 4 had a decrease in visual acuity of > 0.1 logMAR, equivalent to > 1 line on an ETDRS chart, in their better seeing eye, and 3 had a reduction in visual acuity of > 0.2 logMAR in their better eye. Conclusions A limited change in visual acuity was observed in our cohort of 38 patients with XLRS even over an extended period. However, those patients with non-cystic-appearing changes within the fovea, including pigment mottling or an atrophic-appearing lesion, tended to have a more appreciable degree of visual acuity impairment compared with those patients with a cystic-appearing foveal change.
49 citations