What would happen if you transplanted an animal's eyes into a human?
January 13, 2015 3:32 PM   Subscribe

Would a human brain be able to make sense of the information? Would the person see anything at all. Or would the person see exactly like the donor animal (very unlikely I'm guessing).
posted by Gabriel ricci to Science & Nature (14 answers total) 11 users marked this as a favorite
I have a close relative who has keratoconus (sic). He got eye surgery to treat the condition and it took a year to heal the eye to see. After this, I met a man who had had a full corneal transplant. It took him a year to recover vision. I would think that given the time frame, the body would reject the new eyes before vision could return.
posted by parmanparman at 3:53 PM on January 13, 2015 [1 favorite]

Speaking hypothetically to your last question-if it was possible, it'd actually be more likely that the person would see as the animal saw. In our eyes we've got rods and cones, which provide light and color sensitivity. The reason we know that some animals are colorblind is because they lack significant amounts of cones-which is what allows us to pick up colors. Animals with a higher concentration of rods, though, see better in the dark.
So, if we got the transplant eye from one of those animals, it wouldn't matter how our nerves or brain interpreted the info-the physical parts are not there to see in full color.
posted by FirstMateKate at 3:55 PM on January 13, 2015 [3 favorites]

Two major hurdles to answering this:

1) cross-species transplantation is still in very early stages - here's a recent article and a more scientific article from a few years ago with some info you might find helpful.

2) more importantly, human-to-human whole eye transplant hasn't been done successfully - this group recently got a big grant to work on the problem of reconnecting all the optic nerve connections successfully.

I think you're asking in more of a hypothetical sense, but even there, I don't think anyone can make an accurate guess about what would happen without experimental evidence, particularly if you're talking about an animal with very different vision like a dog (as opposed to a primate or something).
posted by randomnity at 3:56 PM on January 13, 2015

Best answer: Just to build on what The World Famous Said -- if you're really talking about whole eye transplant, there are in the vicinity of a million cells that travel from the eye to the brain, and are connected in a specific order that we don't really understand. Before that, each of those million cells connects to as many as several thousand cells in the eye, again in a specific order that we don't really understand.

I suspect what you're really wondering and getting at is what parts of vision happen in the eye versus what parts of vision happen in the brain -- is that right? If so, that's a much more answerable question than this sort of unanswerable hypothetical.
posted by brainmouse at 3:57 PM on January 13, 2015 [5 favorites]

So, if we got the transplant eye from one of those animals, it wouldn't matter how our nerves or brain interpreted the info-the physical parts are not there to see in full color.

This doesn't mean that you would see as the animal saw, though; it means that you would not see color in the way a human can, because there are physical limitations.

The physical apparatus of the eye itself is only part of the story. There is also the issue of how visual perception occurs--which happens in the brain. We don't "see" the raw data, so to speak, from our eyes. It's heavily processed. We can't just assume that after implantation, we would see like a human being, except with fewer colors. We might see like neither human nor dog.

I think you might be right about what this question is getting at, brainmouse. The answer to the hypothetical scenario is probably too close to "it depends on how you do this impossible thing," which isn't satisfying.
posted by Kutsuwamushi at 4:45 PM on January 13, 2015 [3 favorites]

Would a human brain be able to make sense of the information?

The real question is, would the synapses of the neurons right at the point of the graft be even able to recognize the neurotransmitters -- chemical or electrical -- that are coming across?

"Send this image to the brain!"
"And you are...? Your name is..?"
posted by Cool Papa Bell at 4:52 PM on January 13, 2015 [2 favorites]

Beyond what everyone else has already said, though - assuming that you could somehow get over the as-yet insurmountable barriers of cross-species transplantation and wiring up the nerves correctly, it is plausible that you could restore a semblance of vision. Specifically, you could teach the brain to interpret signals to create mental images.

For example, look at tactile-visual substitution: people have learned to interpret electrical stimulation of their tongues in terms of images. So, camera -> array of pixels -> array of electrical on/off pinpricks on the tongue -> image in the brain. There's no reason why you couldn't do that with infra-red night vision, or exotic UV or X-ray sensing: if you have the technological knowhow to successfully transplant animal eyes into humans, you can do better than animal eyes.

(And it's a small step from there to Tally Isham-blue ZEISS IKON eyes...)
posted by RedOrGreen at 7:02 PM on January 13, 2015 [2 favorites]

Perhaps this classic paper from members of the Cybernetics Group will be of interest.
posted by mr vino at 8:20 PM on January 13, 2015

There are also a number of animals, like cuttlefish and (I think) goats, with W shaped pupils that allow them to see polarized light. I imagine the effect would be similar to how some objects look when you wear polarized sunglasses or look at a pair of 3D glasses while wearing another pair of them, sort of shimmery. IIRC, the theory is that this allows them to see prey (or in the case of goats, grass) that has ultra-fine striated structure like the shells of crabs.
posted by sexyrobot at 9:11 PM on January 13, 2015

Here's a neat writeup of how the wolf's eye works.

I've nearly starting skimming this bit about how the retina starts doing edge detection and stuff: http://en.wikipedia.org/wiki/Retina#Spatial_encoding

There's a chance it may answer some of your questions and shape your future ones.
posted by sebastienbailard at 9:12 PM on January 13, 2015 [1 favorite]

So, the development of vision capabilities within the brain is my field of research. As others have pointed out, to actually do this would be impossible with today's technology. However, let's suppose you could use genetics somehow to make it so that an animal's eye would grow instead of a human eye in a developing fetus. (Suppose you worked out issues of size, too.) Would the child once born then develop human-style vision?

First, we have to consider the type of animal whose eye we're using. Mice, for instance, have remarkably poor acuity -- the world is a pretty big blur to them -- and I think a lot of that comes from the physical structure of their eyes, so the child would inherit this. However, there are predators with very good acuity, so let's assume we're using eyes from one of those. And of course there's the issue of color; most mammals can sense 2 rather than 3. Our hypothetical child wouldn't be able to get around this limitation.

What about within the brain? Here, I'd actually be fascinated to see the results, because they would help us answer a lot of unknown questions about the development of vision. Basically, the processing of sensory signals happens due to the precise arrangement of connections between neural cells in the brain. Some amount of this arrangement is determined directly by genes, and some amount of it emerges as a result of the experiences of the animal. But exactly how this is divvied up is an open area of research.

In one of the brain areas dealing with vision, we have cells that respond strongly when we see objects with an edge pointing at a particular angle, say 45°. This type of "edge detection" helps us to recognize the outlines of objects, and hence recognize objects themselves. These cells are able to do this because they have (indirect) connections with cells in the eye that are arranged in a particular pattern. But how do these connections get created in this particular way? Some researchers argue that this property arrises from simple spatial patterning of cells in the eye; given this pattern, connections formed according to a simple genetic rule will automatically have this edge-detection property. If this is how the brain works, then scrambling the pattern of cells in the eye (by substituting an animal eye) would mess up the connections, causing a human to lose the ability to see edges and thus recognize objects.

However, another group of researchers have a different perspective. They argue that edges are an important statistical feature of the world. That is, when we look out and see things, one of the ways what we see differs from random noise is that there are objects with edges all over the place. These researchers argue that brain cells have the ability to learn their connections so that they can respond to these type of statistical features. With this perspective, our hypothetical human's brain would take the incoming signals it receives during development and the early days of life and develop the ability to pull out simple features like edges -- even if the input was scrambled compared to what you'd get from a human eye. And once our human could detect edges, that information would be fed into the other parts of her brain which do more complicated tasks like recognizing objects. At that point, her visual abilities might develop normally.

I'm partial to the second perspective, since my work focuses on how cells could theoretically do this magical task of learning important features from the external world. But as I said, there is still a lot of unresolved science here. Check back in another few decades and see how the answers evolve!
posted by wyzewoman at 9:43 PM on January 13, 2015 [94 favorites]

This is fairly tangental, but I thought this recent thread about human colour vision was pretty interesting.
posted by Ned G at 1:45 AM on January 16, 2015 [1 favorite]

Thanks for that interesting comment wyzewoman. I know he's sort of controversial and in some ways definitely wrong, but one of the points that JJ Gibson made was how much of real-world depth perception is bound up in the passing of an edge of an object in the foreground over the shape of something in the background. For example, we interpret a lampost as closer to a school if we see the edge of the lampost occluding the school behind. This depends on the observer being in motion of course, hence Gibson's interest in the "ecology of visual perception", versus only looking at the optic system, or looking at it experimentally via a motionless undergraduate's pair of eyes clamped into a vice in a lab..... This kind of depth perception is distinction from binocular vision, and I always sort of assumed that it was the major part of depth for animals without overlapping fields of vision. Obviously then the perception of edges would be of crucial importance. I understand that video game designers, for example, are influenced by this.

I used to play squash against a guy with one eye and he was pretty good, surprisingly so maybe, considering in theory he had no depth perception.

Anyway, it caught my eye that you mentioned a focus on edges. Anthropologists at least have some Just-so stories about human/primate vision being about the need to pick fruit in trees and in that story they focus pretty exclusively on binocular vision. It's interesting if the brain is hardwired for perceiving edges.
posted by Rumple at 8:53 AM on January 16, 2015

I remember seeing a film* of a newborn kitten raised in an environment with only horizontal edges (inside a drum painted with wide horizontal stripes). This apparently caused them not to develop circuitry in their eyes/brain to recognize vertical edges. The film showed the kitten unable to see a vertical stick waved in front of it.

This would seem to support wyzewoman's second perspective.

*seen in a mid 70's Open University psych. lecture on BBC2.
posted by monotreme at 6:03 PM on January 19, 2015

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