h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

When considering how we 'see', there is often talk about the brain flipping the inverting the image that is formed on the retina.

I just don't believe that is the case but cannot find any description of the process that says it isn't so

Will somebody please give me some 'insight' on this ....

Sounds about right, the eye works a little like the old-fashioned pin-hole camera...

**runs off to find a picture**

http://www.pbs.org/weta/roughscience/challenges/camera/images/camera_01a.jpg

Yeah, the image created on your retina is upside down. But the brain can easily compensate. Otherwise moving around would be weird.

Thanks good people but this is not what I want to hear.

I want to be told that the popular view of the brain taking the upside down image that forms on the retina and inverting it prior to it being seen by the inner self is just plain wrong....

OK!

"The popular view of the brain taking the upside down image that forms on the retina and inverting it prior to it being seen by the inner self is just plain wrong...."

Unfortunately I'm lieing!

And why do you want to be told that? Does it go against some religious belief of yours?

"And thou shalt not see things upsideth down"

Consider this folks...

On the retina, photons of light fall up 'rods and cones', which react chemically to the photons and in turn send 'messages' into the brain.

I don't believe an 'image' is ever formed on the retina.

I think that what we consider to be an 'image' is our continuously updated view of the world, which is built up and maintained by one part of the brain and 'viewed' by another - probably thousands of other parts. My bottom line is that the image - if it ever actually can be said to exist - is built by the brain.

I just don't beleive that in the process the 'image' is built up one way and THEN goes through some sort of inverting routine.

whoops that should have been 'fall upon'....

The image of the scene _is_ formed on the retina. The same as the image forms on a piece of film or a CCD.

The interpretation of the image is done partly by the cluster of neurons at the back of the eye and partly by the brain.

The brain learns to live with the upside down image as the norm. There was a famous experiment done where a guy wore a pair of glasses that inverted the image before it got to the eye. After a few days (which I expect were fun ) the guys brain said "Ah, that's the norm!" and saw everything as if it were the right way up. After a week or so the guy took them off again, the inverse applied.

Liam.

Hmmm, I guess it all depends on how you define image. I mean you wouldn`t actually be able to take someones eye out and see a little picture formed inside the retina. Although that was believed in old days, hence that scene in Wild Wild West. It is signals that are transferred from the eye to the brain. But the brain does have to mix up those signals, so it doesn`t end up with a wrong image.

Hmm, I suppose that physically, an image _must_ be formed on the retina... after all, some photons must be reflected back off the back of the eye (hence the red-eye in flash photography)... the trouble is that you'd never actually be able to see that image from outside of the eye because of the curvature of the eye itself and the fact there's a lense between any viewer and the back of someones eye.

Physically, the rods and cones at the bottom of the eye are picking up light from above us and those at the top of the eye are picking up light from below us so _somewhere_ in the system our brain must be inverting that signal so that our perception of reality is not opposed to what, for example, our hands feel.

Liam - I saw that experiment on TV not so long ago... it made for some very weird TV pictures

The image that forms on the retina is upside down. But the brain does not need to flip the image. It may do, but we have no knowledge of whether it does or not. The "top of picture" part of the brain may be at the bottom of the brain and the "bottom of picture" may be above it, or in a totally different part of the brain. There is certainly no known "flipping" done.

ooh! something i actually kinda understand! the rods and cones on the retina act like pixels in a digital camera or the little bits of silver nitrate in film. there isn't an actual image there, it's simply that the red cone (rod? i always forget which is which) over there is flashing at your brain, and on the other side theres' a blue, and so on. if you take all these "flashes" form one moment, you could theoretically get a picture something like you see on your computer. however, the picture would be totally reversed -- upside down and right and left switched. and yes, that's how your brain sees it, but when we're little tiny babies we learn that something on that part of the retina is over there in real life, therefor we interpret the world right side up.

Ah - can I correct you there - it's not reversed left to right.

Rods and cones give you colour and luminence (light intensity).

Liam.

I suppose this could boil down to the same problem as that when I look at something that's giving off light at a certain wavelength (for instance 'green', my brain might be processing that in a completely different way from yours, and that _my_ green is might be completely different to what _your_ green is...

whisky -- i've thought of that too, and an implicaiton is that all humans have the same favorite color (as part of being human) but we all have different names for it. hmmm ....

liam -- bah, i've had the summer off, don't expect me to think so hard! thanks for the clarification though.

chickadee said to whisky -- i've thought of that too, and an implicaiton is that all humans have the same favorite color (as part of being human) but we all have different names for it. hmmm ....

... not to mention, through in the fact that so many of us have some amount of color vision deficiency ...



- JD

I haven't the faintest idea what made me spell "throw" like that. Keyboard

- JD

It also depends on the colours around you when you were developing. Primary colours are recommended in nurseries.

People from equatorial countries have a different view of bright colours (there was a New Scientis article on this a few months ago). Bright and garish colours do not seem as bright or garish to them as the would do to someone from more northern or southern climes.

Liam.