Asymmetries in visual acuity around the visual field

Abstract

Human vision is heterogeneous across the visual field. At a fixed eccentricity, performance is better along the horizontal than the vertical meridian, and better 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 meridia or whether, and how far, they extend into the upper and lower hemifields. Here, we measured the extent of the vertical meridian asymmetry by assessing spatial frequency (SF) sensitivity at isoeccentric peripheral locations (10 degree eccentricity), every 15º of polar angle. On each trial, observers judged the orientation (±45º) of a suprathreshold grating stimulus varying in spatial frequency. We estimated 75%-correct SF thresholds, SF cutoff points (i.e., chance-level) and slopes of the psychometric function for each of the 24 isoeccentric locations. We found higher SF sensitivity in the lower than the upper hemifield, with this asymmetry being most pronounced at the vertical meridian and decreasing gradually as the angular distance from the vertical meridian increased. This gradual change in SF sensitivity with polar angle reflected a shift of the psychometric function without reliable changes in slope. The same pattern was found under binocular and monocular conditions. These findings advance our understanding of visual processing around the visual field and help constrain models of visual perception.

Stimulus-dependent contrast sensitivity asymmetries around the visual field

“…Similarly, performance fields asymmetries for SF sensitivity also weaken with increasing angular distance from the VM (Barbot et al, 2020). Notably, these studies are yet to measure contrastdefined performance fields across different stimulus eccentricities or sizes.…”

“…Likewise, performance is better along the lower vertical meridian (LVM) than the upper vertical meridian (UVM) -a phenomenon termed the Vertical-Meridian Asymmetry (VMA) (Carrasco, Talgar, & Cameron, 2001). Together these asymmetries are called performance fields and have been identified for a range of tasks involving contrast sensitivity (Abrams, Nizam, & Carrasco, 2012;Baldwin et al, 2012;Cameron, Tai, & Carrasco, 2002;Levine & McAnany, 2005;Lundh, Lennerstrand, & Derefeldt, 1983;Pointer & Hess, 1989;Regan & Beverley, 1983;Rijsdijk, Kroon, & van der Wildt, 1980;Robson & Graham, 1981;Silva et al, 2008), contrast appearance (Fuller, Rodriguez, & Carrasco, 2008), spatial resolution (Barbot, Xue, & Carrasco, 2020;Carrasco, Williams, & Yeshurun, 2002;Talgar & Carrasco, 2002), temporal information accrual (Carrasco, Giordano, & McElree, 2004), crowding (Fortenbaugh, Silver, & Robertson, 2015;Greenwood, Szinte, Sayim, & Cavanagh, 2017), visual short term memory (Montaser-Kouhsari & Carrasco, 2009), and motion perception (Fuller & Carrasco, 2009).…”

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

“…[73]). This nasal-temporal asymmetry, although interesting, is beyond the focus of this paper, as the asymmetries in performance we observe are found in both binocular and monocular experiments [10, 32]. Overall, the greater emphasis on the horizontal is substantially greater in the mRGCs than the cones.…”

“…The asymmetries gradually fall-off with angular distance from the meridians [74]. This gradual decrease in radial asymmetry in cortex parallels the gradual decrease in contrast sensitivity [10, 25, 26] and spatial frequency sensitivity [32] with angular distance from the cardinal meridians. Measurements of cone density and retinal ganglion cell density have emphasized the meridians, so there is less information regarding how the asymmetries vary with angular distance from the meridians.…”

“…At iso-eccentric locations, performance is better along the horizontal than vertical meridian (horizontal-vertical anisotropy or “HVA” e.g., [9–12]) and better along the lower than upper vertical meridian (vertical-meridian asymmetry or “VMA” [10–14]). These radial asymmetries are observed in many different visual tasks, such as those mediated by contrast sensitivity [10–12, 15–28] and spatial resolution [9, 13, 15, 16, 29–32], contrast appearance [33], visual search [34–42], crowding [14, 42–45], and tasks that are thought to recruit higher visual areas such as visual working memory [31].…”