Recent findings in color vision research imply that humans can perceive a greater range of blue tones than monkeys do.
“Distinct connections present in the human retina may indicate recent evolutionary adaptations for sending enhanced color vision signals from the attention to the brain,” researchers report April 25 within the scientific journal, Proceedings of the National Academy of Sciences.
Yeon Jin Kim, acting instructor, and Dennis M. Dacey, professor, each within the Department of Biological Structure on the University of Washington School of Medicine in Seattle, led the international, collaborative project.
They were joined by Orin S. Packer of the Dacey lab; Andreas Pollreisz on the Medical University of Vienna, Austria; in addition to Paul R. Martin, professor of experimental ophthalmology, and Ulrike Grünert, associate professor of ophthalmology and visual science, each on the University of Sydney, Australia, and the Save Sight Institute.
The scientists compared connections between color-transmitting nerve cells within the retinas of humans with those in two monkeys, the Old World macaque and the Recent World common marmoset. The ancestors of recent humans diverged from these two other primate species roughly 25 million years ago.
By utilizing a tremendous scale microscopic reconstruction method, the researchers wanted to find out of the neural wiring of the areas related to color vision is conserved across these three species, despite each taking their very own independent evolutionary pathways.
The scientists checked out the lightwave-detecting cone cells of the fovea of the retina. This small dimple is densely full of cone cells. It’s the a part of the retina accountable for the sharp visual acuity needed to see vital details, comparable to words on a page or what’s ahead while driving, and for color vision.
Cone cells are available three sensitivities: short, medium and long wavelengths. Details about color comes from neural circuits that process information across different cone types.
The researchers discovered that a certain short-wave or blue sensitive cone circuit present in humans is absent in marmosets. Additionally it is different from the circuit seen within the macaque monkey. Other features the scientists present in the nerve cell connections in human color vision weren’t expected, based on earlier nonhuman primate color vision models.
A greater understanding of the species-specific, complex neural circuitry that codes for color perception could eventually help explain the origins of the colour vision qualities which are distinct to humans.
The researchers also mentioned the likelihood that differences amongst mammals of their visual circuitry might have been at the least partially shaped by their behavioral adaptation to ecological niches. Marmosets live in trees whereas humans prefer to dwell on land. The flexibility to identify ripe fruit among the many shifting light of a forest, for instance, can have offered a selective advantage for particular color visual circuity. Nonetheless, actual effects of environment and behavior on color vision circuitry haven’t yet been established.
More generally, comparative studies of neural circuits at the extent of connections and signaling between nerve cells, the researchers noted, could help answer many other questions. These include elucidating the underlying logic of neural circuit design and providing insight into how evolution has modified the nervous system to assist shape perception and behavior.
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Journal reference:
Kim, Y. J., et al. (2023). Comparative connectomics reveals noncanonical wiring for color vision in human foveal retina. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2300545120.