Presaccadic attention enhances contrast sensitivity, but not at the upper vertical meridian

Abstract

Human visual performance is not only better at the fovea and decreases with eccentricity, but also has striking radial asymmetries around the visual field: At a fixed eccentricity, it is better along (1) the horizontal than vertical meridian and (2) the lower than upper vertical meridian. These asymmetries, known as performance fields, are pervasive -they emerge for many visual dimensions, regardless of head rotation, stimulus orientation or display luminance- and resilient -they are not alleviated by covert exogenous or endogenous attention, deployed in the absence of eye movements. Performance fields have been studied exclusively during eye fixation. However, a major driver of everyday attentional orienting is saccade preparation, during which visual attention automatically shifts to the future eye fixation. This presaccadic shift of attention is considered strong and compulsory, and relies on fundamentally different neural computations and substrates than covert attention. Given these differences, we investigated whether presaccadic attention can compensate for the ubiquitous performance asymmetries observed during eye fixation. Our data replicate polar performance asymmetries during fixation and document the same asymmetries during saccade preparation. Crucially, however, presaccadic attention enhanced contrast sensitivity at the horizontal and lower vertical meridian, but not at the upper vertical meridian. Thus, instead of attenuating polar performance asymmetries, presaccadic attention exacerbates them.

Comparing retinotopic maps of children and adults reveals a late-stage change in how V1 samples the visual field

“…Conversely, adults had more V1 surface area representing the lower than upper vertical meridian, consistent with prior work 18–21 . These findings parallel recent psychophysical findings showing that children have an HVA but no VMA in visual performance 12 , whereas adults have both 13–17,46 . Nonetheless, the fMRI data do not perfectly match the psychophysical data.…”

“…Conversely, adults had more V1 surface area representing the lower than upper vertical meridian, consistent with prior work (Benson et al, 2021a; Himmelberg et al, 2021, 2022a; Silva et al, 2018). These findings parallel recent psychophysical findings showing that children have an HVA but no VMA in visual performance (Carrasco et al, 2022), whereas adults have both (Abrams et al, 2012; Barbot et al, 2021; Carrasco et al, 2001; Greenwood et al, 2017; Hanning et al, 2022; Himmelberg et al, 2020). Nonetheless, the fMRI data do not perfectly match the psychophysical data.…”

Linking individual differences in human primary visual cortex to contrast sensitivity around the visual field

“…The HVA and VMA are found in tasks involving contrast sensitivity (13,14,16,(47)(48)(49)(50)(51)(52)(53), perceived contrast (54), spatial resolution (15,55,56), temporal information accrual (57), illusory motion perception (17) and visual short term memory (58). Further, these polar angle asymmetries are pervasive across a range of conditions; they exist across luminance levels ( 13), binocular and monocular stimulation (13,15), different stimulus orientations (13,48,53), eccentricities and spatial frequencies (13,14,16,48) as well as covert attentional conditions (13,14,18,19).…”

“…This is reflected in the cortical magnification function, in which V1 surface area is greatest at the fovea and decreases with increasing eccentricity 2,7,9,11,[19][20][21] . Visual performance for many tasks (including contrast sensitivity) also changes as a function of polar angle; it is better along the horizontal than vertical meridian (horizontal-vertical anisotropy, HVA), and along the lower than upper vertical meridian (vertical meridian asymmetry, VMA) 12,[22][23][24][25][26][27] . These perceptual polar angle asymmetries have been linked to similar asymmetries in V1 cortical magnification: in humans and macaque monkey, more local V1 surface area is dedicated to processing the horizontal than vertical meridian (i.e., a cortical HVA) and the lower than upper vertical meridian (i.e., a cortical VMA) [8][9][10]28 .…”

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

“…The HVA and VMA are found in tasks involving contrast sensitivity 13,14,16,[48][49][50][51][52][53][54] , perceived contrast 55 , spatial resolution 15,56,57 , temporal information accrual 58 , illusory motion perception 17 and visual short term memory 59 . Further, these polar angle asymmetries are pervasive across a range of conditions; they exist across luminance levels 13 , binocular and monocular stimulation 13,15 , different stimulus orientations 13,49,54 , eccentricities and spatial frequencies 13,14,16,49 as well as covert attentional conditions 13,14,18,19 .…”