Protein found in robins’ eyes has all the hallmarks of a magnetoreceptor
the-scientist.com
the-scientist.com
I watch a lot of TV and I know a lot of really cool or funny quotes, but this one, it's impactful.
I had a colleague once who had a stroke and described his vision afterwards as looking though splintered glass. After a while, he explained he didn’t perceive it anymore and that his brain just decided to “workaround” the issue making new connections where needed.
I think having some “sense” of magnetic fields could be very subtle, like just a feeling of which direction you’re facing when you’re turning around (you could argue you already use the position of the sun this way, subconsciously).
People into body mods who get a magnetic implant often describe it as a sixth sense [1].
Ocular migraines will give the splintered glass effect. They are temporary however.
Hanne Theon and colleagues trained mantis shrimp to attack squares of certain colors to get food rewards. Attacks on other “distractor” squares weren’t rewarded. By varying the color of those distractors, one can measure the spectral sensitivity of their visual system. Using similar methods, humans can distinguish between wavelengths a few nm apart; mantis shrimp are more like 20 nm.
This is disappointing, but the reason is pretty wild. Most animals have “color opponency”: circuits early in the visual system convert the photoreceptors’ output into a differential representation: the intensity of red light here minus the intensity of green light in the surrounding neighborhood. This mechanism “normalizes” for the total amount of light, thereby letting you separately perceive hue and brightness, and has some other nice properties.
Mantis Shrimp took a different path. There’s no obvious inhibitory interaction between the photoreceptors. They may therefore separately perceive redness, greenness, blueness, etc, but without combining these streams of information, their color acuity is poor. Interestingly, they do a “scanning” behavior that sort of recreates the opponency by dragging different types of photoreceptors across the same part of the visual world.
Thoen, H. H., How, M. J., Chiou, T. H., & Marshall, J. (2014). A different form of color vision in mantis shrimp. Science, 343(6169), 411–413. http://dx.doi.org/ 10.1126/science.1245824
https://www.researchgate.net/profile/Tsyr-Huei-Chiou/publica...
See for an interesting read: https://www.pnas.org/content/113/6/1654
Many or maybe most humans can also see the polarity of light. Take your smart phone and make the screen display a white image. While it shows this image for a long time, rotate the phone. You should see a yellow whispy checkerboard pattern turning with the phone. This "brush" is actually a visible measurement of the polarity of the light coming from the phone.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528539/
I don't know if there's any mechanism for which humans can detect magnetic polarity, but there's research on this too:
https://www.the-scientist.com/news-opinion/can-humans-sense-...
https://elifesciences.org/articles/17210
Oh wow, didn't even realize Anikeeva and Jasanoff had written on this, too:
https://elifesciences.org/articles/19569
Just too much snake oil in this field -- in top Nature journals, nonetheless. It's funny, when I was an undergrad I took a research idea to Alan Jasanoff and he rejected it with similarly simple back-of-the-envelope math. Guess he has a knack for sniffing out BS.
Bird Navigation Based On Quantum Zeno Effect
from the schroedinger's-parrot dept.
2008 on /.
Unravelling the enigma of bird magnetoreception - https://news.ycombinator.com/item?id=27610181 - June 2021 (9 comments)
The thought I was expressing is that there seems to be no separate organ at all here and that seems unexpected to me. I would expect there to at least be something like a specialized region. Not just that the eye in general happens to also have this ability.