Eli5: the lens of your eye flips the image of what is happening in front of you and displays it on your retina, then your brain “flips” it again for you to perceive. What is the brain doing for that second flip?
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The brain is just orienting the image properly to your perception of your body. It has made and is maintaining a neural connection between the top of the image and your feet, essentially.
It’s basically just the orientation of the nerves that connect the centre of the brain that receives the sight impulses to the part of the brain that puts it together as a comprehensible picture , those fibres travel upside down to flip it back
Edit,
Actually I mean it’s the nerves from the retina that go to the centre that receives that travels upside down I think
Either way you get the point
(Sorry, my neurology is rusty)
Your brain doesn’t know that the image on the retina is inverted, and it doesn’t need to. All it needs to know is that a signal from a particular neuron corresponds to detecting light in one area of your vision, and a different neuron corresponds to a different area.
It’s just your brain deciding that it’s stupid to have things upside down and deciding not to anymore.
An experiment was done where they had volunteers put on goggles that flipped everything upside down. They wore them all the time: sleeping, showering, everywhere all the time.
After about a week, the brain said “screw this, this is dumb” and flipped everything right side up again, and the volunteers functioned normally. They still had the flipping goggles on, and their brain just undid it.
At the end of the experiment they took the goggles off, and everything was upside down again. And again, after a week or so, the brain flipped everything back again.
Your brain just makes stuff up about what you see. It does a tremendous amount of image processing. Your eyes move and wiggle small amounts constantly, it fixes that and makes things appear steady. Your eyes suck at color in your peripheral vision, your brain remembers what color things are and what life should look like and fills things in. You have a blind spot in each eye that you can only notice if you specifically trick your brain at failing at fixing it.
There is no “ground truth” in what you see. It’s all interpreted, from shapes to contrast to color.
Your brain isn’t doing anything. It simply detects light and movement from your retina that’s wired to specific parts of your brain. A lot of it is the the brain “learns to see” in your very early months. The brain learns which movements and locations of light mean what things. Animals that have their eyes covered for a few weeks after birth often end up effectively blind because the part of the brain that should process the eye never “learned” by experience to process vision. [Horrible experiment here…](https://journals.physiology.org/doi/pdf/10.1152/jn.1965.28.6.1029)
A simple analogy to the wiring part of this is to rotate a calculator 180 degrees on your desk. The buttons and display are visible, but upside down. Now do math. The results are still correct. Even though the inputs to the calculator are “upside down”, the wiring is such that it knows which signal came from which button and it’s still able to produce a correct result.
As to the learning part. Imagine teaching a kid a game with abstract shapes. They will quickly learn which shapes mean which things. Now take another kid (who has never heard of the game) and teach them the same game, but the shapes are rotated 180 degrees. They will learn the game just as quickly.
Its been a while, but I saw this short documentary where a guy made glasses that flipped the images yet again. It did not take very long for the subject to be able to act normally.
What does a newly born baby see?
I don’t think it flips it at all. What would it even mean? There is no second projection. The image is projected on the retina, right? Like on a photographic material. And it’s not projected anymore so it doesn’t need to be “flipped”. Top pixels of the retina are just interpreted by the brain as the bottom of the original image. How does the brain know? You move your hand down, the retina pixels register the motion from lower ones to the upper ones. The mapping is original. It’s learned. The pixels can be assigned to random neurons, random “memory cells”, however, when you learn to see (and this is making sense of pixel data transmitted to the brain) you learn which pixels correspond to a particular area of the visible space around you.
The brain is a computer made of smaller computers. Its “camera” is a computer. Then you have a bigger computer which is the visual cortex. Then it’s a bigger computer that is your frontal lobes, a kind of a CPU, that gathers data from the smaller computers and makes a kind of sense of it. BTW, regular computers works similarly. They have a lot of chips that takes care of some details, they feed the results to other chips that work with the results.
Also, in some computers, like microcontrollers, you can map inputs and outputs to different physical signals. Let’s say you have some light sensors and some temperature sensors. It doesn’t matter where physically you connect the signals, you can map what goes where in the software.
Also, as I designed some machines like that – the machine can automatically detect what is connected to it. When we get certain data from certain inputs – we know what is connected where. It’s pretty convenient, because we don’t need to worry where we connect particular wires. We read the data and we know “oh, there it is”. ELI5, so let’s leave it why that automatic detection is rarely used and in machines we mostly depend on pre-determined connections. It doesn’t matter here, what’s important it’s possible, it’s pretty easy and that’s most probably how protein computers do that. It’s logical, since most of their programming and operation is achieved by the learning process.
You’ve probably heard about AI. It mimics how living brains work. It just learns how to connect the dots. You connect the dots wrong – you get “weaker” signal, you connect the dots right, you get stronger signal. If brain sees that connecting pixel data from the top retina pixels matches the data coming from the other senses, it’s the feedback it needs to build the correct spatial awareness.
How do you know the brain flips it again? Maybe we are used to seeing everything upside down.
So here’s the really fun part:
We tend to think of our eyes sort of like windows that we use to look out at the world. The reality is light is falling on special cells in the back of your eye that create tiny electrical impulses when they’re exposed to light. Those impulses then travel along your optic nerve to your brain which interprets those signals and presents them to you as an image.
Or to put it another way… see the screen you’re reading this on now? No you don’t. What you’re experiencing is a mental ‘simulation’ of that screen, wholly made up by your brain based on a stream of electrical pulses.
This is how optical illusions work, why our eyes are so easily ‘tricked’ because you’re not seeing through a window into reality, you’re seeing a simulation created by your brain that it editing that image on the fly to give you what it *believes* is there, emphasising important stuff while filtering out what doesn’t need your attention.
For example, both your eyes have a blind spot where your optic nerve meets your retina… but your brain just edits it out. Every time your eyes move, for the split second they’re moving, your brain cuts off the signal and you go blind to prevent motion sickness. Why don’t you notice? Because your brain is just editing your perception on the fly.
Here’s the really mind-blowing part about this: Do you know when you look at a clock and the second hand seems to stay still for a fraction of a second too long, then goes back to it’s normal movement when you keep looking at it? That’s because you went blind for a split second while your eyes moved to it… and then your brain took the image of that clock and edited it into your memory of that split second you were blind so you didn’t notice.
A lot of optical illusions work because your brain is *expecting* to see one thing and is presenting that to you because it can’t properly make sense of what is actually there.
So, with all that going on, flipping an image is not exactly a big ask for your brain to do.
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