Simultaneous changes in visual acuity, cortical population receptive field size, visual field map size, and retinal thickness in healthy human aging

Abstract

Healthy human aging is associated with a deterioration of visual acuity, retinal thinning, visual field map shrinkage and increasing population receptive field sizes. Here we ask how these changes are related to each other in a cross-sectional sample of fifty healthy adults aged 20–80 years. We hypothesized that age-related loss of macular retinal ganglion cells may lead to decreased visual field map sizes, and both may lead to increased pRF sizes in the cortical central visual field representation. We measured our participants’ perceptual corrected visual acuity using standard ophthalmological letter charts. We then measured their early visual field map (V1, V2 and V3) functional population receptive field (pRF) sizes and structural surface areas using fMRI, and their retinal structure using high-definition optical coherence tomography. With increasing age visual acuity decreased, pRF sizes increased, visual field maps surface areas (but not whole-brain surface areas) decreased, and retinal thickness decreased. Among these measures, only functional pRF sizes predicted perceptual visual acuity, and Bayesian statistics support a null relationship between visual acuity and cortical or retinal structure. However, pRF sizes were in turn predicted by cortical structure only (visual field map surface areas), which were only predicted by retinal structure (thickness). These results suggest that simultaneous disruptions of neural structure and function throughout the early visual system may underlie the deterioration of perceptual visual acuity in healthy aging.

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

“…This relation holds irrespective of the cortical depth used to compute surface area (gray/pial boundary, gray/white boundary, or half-way between them). V1 surface area has been shown to correlate with a few measurements of visual performance, such as perceptual acuity thresholds (42,43), orientation discrimination thresholds (but not contrast discrimination thresholds) (44), and measurements of subjective object size (41). Nonetheless, performance on most visual tasks have not been compared to V1 size, and there is not yet a computational account that would enable one to predict to what extent, if any, performance on different tasks would be affected by V1 size.…”

“…We focused on the relation between performance on one visual measure -contrast sensitivityand the size of the one cortical map -V1. Although V1 size has been linked to a few perceptual measures (41)(42)(43)(44), it is likely that there will be other measures for which performance is better explained by the size of other visual areas. Such an outcome is possible because the sizes of different maps are at least partially independent (2,4).…”

“…Does this compression represent fewer overall neurons, or is neural count similar across individuals and instead this compression represents increased neural density? The fact that performance on at least some tasks correlates with V1 surface area [42][43][44][45] implies that a smaller V1 likely has fewer overall neurons, but the histological measures to assess this do not yet exist. Differences in V1 neural counts among individuals and across polar angle, raise the question of how the neural code varies across individuals and visual field location.…”

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

“…This relation holds irrespective of the cortical depth used to compute surface area (gray/pial boundary, gray/white boundary, or half-way between them). V1 surface area has been shown to correlate with a few measurements of visual performance, such as perceptual acuity thresholds 43,44 , orientation discrimination thresholds (but not contrast discrimination thresholds) 45 , and measurements of subjective object size 42 . Nonetheless, performance on most visual tasks have not been compared to V1 size, and there is not yet a computational account that would enable one to predict to what extent, if any, performance on different tasks would be affected by V1 size.…”

Understanding structure–function relationships in the mammalian visual system: part one

“…Alvarez et al (2021) report that human V1 shows larger population receptive fields (pRF; Dumoulin and Wandell 2008) for disparity-defined stimuli, compared with other types of stimuli, and that this observation can be explained based on the binocular energy model (Ohzawa et al 1990). Further, Silva et al (2021) report that pRF estimates are affected by aging, revealing correlations between visual acuity, retinal thickness, and cortical visual area size in human participants. In addition, Brown et al (2021) build on the topic of adult brain plasticity using a simulated lesion approach, supplementing earlier investigations of the source of stimulus-evoked blood oxygen level-dependent (BOLD) responses in V1 of human macular degeneration patients (Baker et al 2005;Masuda et al 2020).…”