scholarly journals Asymmetries in visual acuity around the visual field

2020 ◽  
Author(s):  
Antoine Barbot ◽  
Shutian Xue ◽  
Marisa Carrasco
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Psychometric Function ◽  
Spatial Resolution ◽  
Visual Processing ◽  
Polar Angle ◽  
Angular Distance ◽  
Human Vision ◽  
Gradual Change ◽  
Vertical Meridian

Human vision is heterogeneous around the visual field. At a fixed eccentricity, performance is better along the horizontal than the vertical meridian, and along the lower than the upper vertical meridian. These asymmetric patterns, termed performance fields, have been found in numerous visual tasks, including those mediated by contrast sensitivity and spatial resolution. However, it is unknown whether spatial resolution asymmetries are confined to the cardinal meridians or whether, and how far, they extend into the upper and lower hemifields. Here, we measured visual acuity at isoeccentric peripheral locations (10 deg eccentricity), every 15º of polar angle. On each trial, observers judged the orientation (±45º) of one out of four equidistant, suprathreshold grating stimuli varying in spatial frequency (SF). On each block, we measured performance as a function of stimulus SF at 4 out of 24 isoeccentric locations. We estimated the 75%-correct SF threshold, SF cutoff point (i.e., chance-level) and slope of the psychometric function for each location. We found higher SF estimates –i.e., better acuity– for the horizontal than the vertical meridian, and for the lower than the upper vertical meridian. These asymmetries were most pronounced at the cardinal meridians and decreased gradually as the angular distance from the vertical meridian increased. This gradual change in acuity with polar angle reflected a shift of the psychometric function without changes in slope. The same pattern was found under binocular and monocular viewing conditions. These findings advance our understanding of visual processing around the visual field and help constrain models of visual perception.

scholarly journals Cortical Magnification in Human Visual Cortex Parallels Task Performance around the Visual Field

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Noah C Benson ◽  
Eline R Kupers ◽  
Antoine Babot ◽  
Marisa Carrasco ◽  
Jonathan Winawer
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Polar Angle ◽  
Monozygotic Twin ◽  
Human Vision ◽  
Retinal Cell ◽  
Vertical Meridian ◽  
Cortical Magnification ◽  
Cell Densities ◽  
And Behavior

Human vision has striking radial asymmetries, with performance on many tasks varying sharply with stimulus polar angle. Performance is generally better on the horizontal than vertical meridian, and on the lower than upper vertical meridian, and these asymmetries decrease gradually with deviation from the vertical meridian. Here we report cortical magnification at a fine angular resolution around the visual field. This precision enables comparisons between cortical magnification and behavior, between cortical magnification and retinal cell densities, and between cortical magnification in twin pairs. We show that cortical magnification in human primary visual cortex, measured in 163 subjects, varies substantially around the visual field, with a pattern similar to behavior. These radial asymmetries in cortex are larger than those found in the retina, and they are correlated between monozygotic twin pairs. These findings indicate a tight link between cortical topography and behavior, and suggest that visual field asymmetries are partly heritable.

scholarly journals Cortical Magnification in Human Visual Cortex Parallels Task Performance around the Visual Field

2020 ◽  
Author(s):  
Noah C. Benson ◽  
Eline R. Kupers ◽  
Antoine Barbot ◽  
Marisa Carrasco ◽  
Jonathan Winawer
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Polar Angle ◽  
Monozygotic Twin ◽  
Human Vision ◽  
Retinal Cell ◽  
Vertical Meridian ◽  
Cortical Magnification ◽  
Cell Densities ◽  
And Behavior

AbstractHuman vision has striking radial asymmetries, with performance on many tasks varying sharply with stimulus polar angle. Performance is better on the horizontal than vertical meridian, and on the lower than upper vertical meridian, and these asymmetries decrease gradually with deviation from the vertical meridian. Here we report cortical magnification at a fine angular resolution around the visual field. This precision enables comparisons between cortical magnification and behavior, between cortical magnification and retinal cell densities, and between cortical magnification in twin pairs. We show that cortical magnification in human primary visual cortex, measured in 181 subjects, varies around the visual field, with a pattern similar to behavior. We find that these cortical asymmetries are larger than those found in the retina, and that they are correlated between monozygotic twin pairs. These novel findings indicate a tight link between cortical topography and behavior, and suggest that visual field asymmetries are, at least in part, heritable.

scholarly journals Asymmetries around the visual field: From retina to cortex to behavior

2022 ◽  
Vol 18 (1) ◽  
pp. e1009771
Author(s):  
Eline R. Kupers ◽  
Noah C. Benson ◽  
Marisa Carrasco ◽  
Jonathan Winawer
Keyword(s):  
Visual Field ◽  
Visual Processing ◽  
Polar Angle ◽  
Spatial Filtering ◽  
Orientation Discrimination ◽  
Support Vector ◽  
Additional Contribution ◽  
Full Account ◽  
Observer Model ◽  
Cone Density

Visual performance varies around the visual field. It is best near the fovea compared to the periphery, and at iso-eccentric locations it is best on the horizontal, intermediate on the lower, and poorest on the upper meridian. The fovea-to-periphery performance decline is linked to the decreases in cone density, retinal ganglion cell (RGC) density, and V1 cortical magnification factor (CMF) as eccentricity increases. The origins of polar angle asymmetries are not well understood. Optical quality and cone density vary across the retina, but recent computational modeling has shown that these factors can only account for a small percentage of behavior. Here, we investigate how visual processing beyond the cone photon absorptions contributes to polar angle asymmetries in performance. First, we quantify the extent of asymmetries in cone density, midget RGC density, and V1 CMF. We find that both polar angle asymmetries and eccentricity gradients increase from cones to mRGCs, and from mRGCs to cortex. Second, we extend our previously published computational observer model to quantify the contribution of phototransduction by the cones and spatial filtering by mRGCs to behavioral asymmetries. Starting with photons emitted by a visual display, the model simulates the effect of human optics, cone isomerizations, phototransduction, and mRGC spatial filtering. The model performs a forced choice orientation discrimination task on mRGC responses using a linear support vector machine classifier. The model shows that asymmetries in a decision maker’s performance across polar angle are greater when assessing the photocurrents than when assessing isomerizations and are greater still when assessing mRGC signals. Nonetheless, the polar angle asymmetries of the mRGC outputs are still considerably smaller than those observed from human performance. We conclude that cone isomerizations, phototransduction, and the spatial filtering properties of mRGCs contribute to polar angle performance differences, but that a full account of these differences will entail additional contribution from cortical representations.

scholarly journals Identification of the ventral occipital visual field maps in the human brain

2016 ◽  
Author(s):  
Jonathan Winawer ◽  
Nathan Witthoft
Keyword(s):  
Visual Field ◽  
Human Brain ◽  
Human Subjects ◽  
Polar Angle ◽  
Vertical Meridian ◽  
Retinotopic Mapping ◽  
Collateral Sulcus ◽  
Anatomical Images ◽  
Visual Field Maps ◽  
Magnetic Resonance Imaging Mri

The location and topography of the first three visual field maps in the human brain, V1-V3, are well agreed upon and routinely measured across most laboratories. The position of 4th visual field map, "hV4", is identified with less consistency in the neuroimaging literature. Using magnetic resonance imaging (MRI) data, we describe landmarks to help identify the position and borders of hV4. The data consist of anatomical images, visualized as cortical meshes to highlight the sulcal and gyral patterns, and functional data obtained from retinotopic mapping experiments, visualized as eccentricity and angle maps on the cortical surface. Several features of the functional and anatomical data can be found across nearly all subjects and are helpful for identifying the location and extent of the hV4 map. The medial border of hV4 is shared with the posterior, ventral portion of V3, and is marked by a retinotopic representation of the upper vertical meridian. The anterior border of hV4 is shared with the VO-1 map, and falls on a retinotopic representation of the peripheral visual field, usually coincident with the posterior transverse collateral sulcus. The ventro-lateral edge of the map typically falls on the inferior occipital gyrus, where functional MRI artifacts often obscure the retinotopic data. Finally, we demonstrate the continuity of retinotopic parameters between hV4 and its neighbors; hV4 and V3v contain iso-eccentricity lines in register, whereas hV4 and VO-1 contain iso-polar angle lines in register. Together, the multiple constraints allow for a consistent identification of the hV4 map across most human subjects.

scholarly journals Linking individual differences in human V1 to perception around the visual field

2021 ◽  
Author(s):  
Marc Himmelberg ◽  
Jonathan Winawer ◽  
Marisa Carrasco
Keyword(s):  
Individual Differences ◽  
Visual Field ◽  
Contrast Sensitivity ◽  
Polar Angle ◽  
Strongly Correlated ◽  
Ideal Model ◽  
Vertical Meridian ◽  
Perceptual Contrast ◽  
Cortical Magnification ◽  
Ideal Model System

Abstract A central question in neuroscience is how the organization of cortical maps relates to perception, for which human primary visual cortex (V1) is an ideal model system. V1 nonuniformly samples the retinal image, with greater cortical magnification (surface area per degree of visual field) at the fovea than periphery, and at the horizontal than vertical meridian. Moreover, the size and organization of V1 differs greatly across individuals. Here, we used fMRI and psychophysics in the same individuals to quantify individual differences in V1 cortical magnification and perceptual contrast sensitivity at the four polar angle meridians. Across individuals, the overall size of V1 and localized cortical magnification both positively correlated with contrast sensitivity. Moreover, increases in cortical magnification and contrast sensitivity at the horizontal compared to the vertical meridian were strongly correlated. These data reveal a tight link between cortical anatomy and visual perception at the level of individual observer and stimulus location.

scholarly journals Identification of the ventral occipital visual field maps in the human brain

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1526 ◽  
Author(s):  
Jonathan Winawer ◽  
Nathan Witthoft
Keyword(s):  
Visual Field ◽  
Human Brain ◽  
Human Subjects ◽  
Polar Angle ◽  
Imaging Data ◽  
Vertical Meridian ◽  
Retinotopic Mapping ◽  
Collateral Sulcus ◽  
Anatomical Images ◽  
Visual Field Maps

The location and topography of the first three visual field maps in the human brain, V1-V3, are well agreed upon and routinely measured across most laboratories. The position of 4th visual field map, ‘hV4’, is identified with less consistency in the neuroimaging literature.  Using magnetic resonance imaging data, we describe landmarks to help identify the position and borders of ‘hV4’. The data consist of anatomical images, visualized as cortical meshes to highlight the sulcal and gyral patterns, and functional data obtained from retinotopic mapping experiments, visualized as eccentricity and angle maps on the cortical surface. Several features of the functional and anatomical data can be found across nearly all subjects and are helpful for identifying the location and extent of the hV4 map. The medial border of hV4 is shared with the posterior, ventral portion of V3, and is marked by a retinotopic representation of the upper vertical meridian. The anterior border of hV4 is shared with the VO-1 map, and falls on a retinotopic representation of the peripheral visual field, usually coincident with the posterior transverse collateral sulcus. The ventro-lateral edge of the map typically falls on the inferior occipital gyrus, where functional MRI artifacts often obscure the retinotopic data. Finally, we demonstrate the continuity of retinotopic parameters between hV4 and its neighbors; hV4 and V3v contain iso-eccentricity lines in register, whereas hV4 and VO-1 contain iso-polar angle lines in register. Together, the multiple constraints allow for a consistent identification of the hV4 map across most human subjects.

Role of Visual Acuity in Tachistoscopic Recognition of Three-Letter Words

1974 ◽  
Vol 38 (3) ◽  
pp. 755-761 ◽  
Author(s):  
Frank Curcio ◽  
William Mackavey ◽  
Jeffrey Rosen
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Word Recognition ◽  
Right Visual Field ◽  
Gap Detection ◽  
Vertical Meridian ◽  
Line Target ◽  
Tachistoscopic Recognition ◽  
The Right

It has been suggested that a correlation between word recognition and visual acuity would constitute a confounding influence in word-recognition studies within a laterality paradigm. 20 Ss made binary judgments concerning the presence or absence of a spatial gap in a tachistoscopically presented line target positioned at .75°, 1.5°, 3.0°, and 6.0° in either visual field. Gap detection was superior in the right visual field ( p = .02) at the 6.0° position. Word recognition was determined for tachistoscopically presented three-letter words positioned along a 6.0° vertical meridian in either visual field. Visual acuity performance was not related to word recognition either for the group or for individual Ss. The data therefore do not encourage the view that normal variations in acuity significantly affect word recognition in laterality studies.

scholarly journals Epidemiological Findings of Refractive Errors and Amblyopia among the Schoolchildren in Hatta Region of the United Arab Emirates

2021 ◽  
pp. 1-7
Author(s):  
Salam Chettian Kandi ◽  
Hayat Ahmad Khan
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
United Arab Emirates ◽  
Refractive Error ◽  
Screening Program ◽  
Low Vision ◽  
Refractive Errors ◽  
Vision Screening ◽  
Screening Programs ◽  
School Based

<b><i>Introduction:</i></b> Uncorrected refractive errors and amblyopia pose a major problem affecting schoolchildren. We had previously observed that many schoolchildren in the Hatta region presented to the ophthalmology clinic with uncorrected refractive errors and amblyopia, which led us to undertake this research. As per the WHO, the term “visual impairment” can be “low vision” or “blindness.” Based on the presenting vision, “low vision” is defined for children who have vision of &#x3c;6/18 to 3/60 or having visual field loss to &#x3c;20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of &#x3c;3/60 or corresponding visual field of &#x3c;10°. <b><i>Purpose:</i></b> To estimate the magnitude of uncorrected refractive errors and amblyopia among the schoolchildren aged 6–19 years and to assess the efficacy of school-based refractive error screening programs in the Hatta region of the United Arab Emirates. <b><i>Methods:</i></b> An epidemiological, cross-sectional, descriptive study was conducted on the entire student population studying in the government schools of the region. Those who failed the Snellen visual acuity chart test and those who were wearing spectacles were evaluated comprehensively by the researcher in the Department of Ophthalmology of the Hatta Hospital. Data were entered in the Refractive Error Study in School Children (RESC) eye examination form recommended by the WHO, and were later transferred to Excel sheets and analyzed by SPSS. <b><i>Results:</i></b> 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (<i>n</i> = 340) had impaired vision with 20.9% (<i>n</i> = 333) refractive errors, of which 58% were uncorrected. Among the refractive error group, 19% (64 subjects) had amblyopia (4% of total students). The incidence of low vision was 9.5% and blindness was 0.38%. Low vision was found to be 9.5% and blindness 0.38%, taking in to account presenting visual acuity rather than best-corrected visual acuity for defining low vision and blindness. <b><i>Conclusion:</i></b> A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, <i>n</i> = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (<i>n</i> = 50) were found to be in the 11–19 years age group. Noncompliance with optical corrections was the reason for the high number of cases. A rigorous vision screening program and refractive services, complimented with awareness among parents and teachers, are recommended.

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