The Verriest Lecture: Short-wave-sensitive cone pathways across the life span

Abstract

Structurally and functionally, the short-wave-sensitive (S) cone pathways are thought to decline more rapidly with normal aging than the middle- and long-wave-sensitive cone pathways. This would explain the celebrated results by Verriest and others demonstrating that the largest age-related color discrimination losses occur for stimuli on a tritan axis. Here, we challenge convention, arguing from psychophysical data that selective S-cone pathway losses do not cause declines in color discrimination. We show substantial declines in chromatic detection and discrimination, as well as in temporal and spatial vision tasks, that are mediated by S-cone pathways. These functional losses are not, however, unique to S-cone pathways. Finally, despite reduced photon capture by S cones, their postreceptoral pathways provide robust signals for the visual system to renormalize itself to maintain nearly stable color perception across the life span.

No evidence for loss of short-wavelength sensitive cone photoreceptors in normal ageing of the primate retina

“…S-cones have distinct anatomical and physiological properties compared to M/L cones 6 7 . Also, colour discrimination studies show that the S-cone pathway is selectively affected by age and disease 8 9 10 11 . The ageing effect was thought to relate to brunescence of the lens as this would selectively absorb shorter wavelengths 8 .…”

“…Also, colour discrimination studies show that the S-cone pathway is selectively affected by age and disease 8 9 10 11 . The ageing effect was thought to relate to brunescence of the lens as this would selectively absorb shorter wavelengths 8 . However, there are also significant changes in S-cone timing with age that are not related to lens brunescence 12 .…”

Mitochondrial absorption of short wavelength light drives primate blue retinal cones into glycolysis which may increase their pace of aging

“…AGEs are also associated with diabetes and macular degeneration (Glenn & Stitt, 2009; Sun et al, 2017; Uribarri et al, 2010). Such processes may underpin the selective early decline in aged human S-cone function (Werner, 2016). As primate S-cones are not lost with age (Weinrich et al, 2017), their functional decline is likely due to their distinct metabolism.…”

“…As primate S-cones are not lost with age (Weinrich et al, 2017), their functional decline is likely due to their distinct metabolism. However, throughout the vast majority of human evolution, lifespan was probably <40 years, which is an age prior to significant human S-cone decline (Werner, 2016). Hence, adoption of glycolysis would have carried little cost when lifespan was short.…”

“…The price paid for reducing mitochondria is increased reliance on glycolysis with its inherent problems from an increased pace of ageing 6 . However, throughout the vast majority of human evolution, lifespan was probably <40 years, which is an age prior to significant human S cone decline 4 . Hence, adoption of glycolysis would have carried little cost.…”