Seeing colors

[Zolar V]

In the eye of a mammal, lets say a human or a primate, is it the rods and stuff in the eye or the brain itself that cannot process infrared and ultraviolet electromagnetic frequencies?

[Kyrisch]

It's not that the rods and cones cannot 'process' those wavelengths, but rather that they are not physically sensitive to light whose wavelengths are not in the visible spectrum.

[Zolar V]

so, theoretically we could inject those frequencies into the ocular nerve, bypassing the rods and cones. Of course we would have to get the proper infrared and ultraviolet frequencies to inject.

[ecoli]

i don't imagine that the brain would know how to interpret that information.

[Icefire]

i don't imagine that the brain would know how to interpret that information.

 

Eventually, possibly.

I recall an article a while ago where a man that was born with defective eyes had transplants in his 30s or something. At first he couldn't make out anything because his visual centre was underdeveloped, but as time went on his spacial processing abilities improved a bit, but he still had to shave in the dark and it was extremely confusing. He eventually had a stroke, making him blind again.

 

In this case: Since we are just adding new information to an already developed visual centre, it shouldn't be too hard for the brain to begin to understand this new information. It'll still take a while to adapt, but it should work.

 

It would be very cool, because for Infared you would be able to detect temperature changes easily

I can't go to school mommy, I have a fever

:glance: No you don't. now get out of bed and get ready.

 

But for both spectrums, things and people will look significantly different, which can be a major shock.

[CharonY]

The brain only processes signals coming from the nerves. It does not concern itself about the origin of the signal (i.e. whether they are from light in the visible range or by direct excitation). If you punch yourself in the eye you can elicit unspecific action potentials that will be interpreted by the brain as light flashes). There are no differences in the "frequencies", the light just elicits the cones with different efficiency and the summary signals in intermediate neurons moving to the brain will then interpret it as a given color. So if you exchange a rod that adsorbs e.g. red most effectively and exchange it with one that reacts to UV your brain would interpret UV as red.

[Zolar V]

The brain only processes signals coming from the nerves. It does not concern itself about the origin of the signal (i.e. whether they are from light in the visible range or by direct excitation). If you punch yourself in the eye you can elicit unspecific action potentials that will be interpreted by the brain as light flashes). There are no differences in the "frequencies", the light just elicits the cones with different efficiency and the summary signals in intermediate neurons moving to the brain will then interpret it as a given color. So if you exchange a rod that adsorbs e.g. red most effectively and exchange it with one that reacts to UV your brain would interpret UV as red.

 

So, if you were to collect the frequency patterns from optical stimulation, you could find the probable frequency that the rod/cone would transmit into the nerve?

 

^^ i actually had the idea of this in a dream...... about cyberization. and an experiment to collect the data needed to do such things.

 

I am going to outline my experiment.

 

Hypothesis: Using current technology you can inject data through a nerve/computer connection to the brain. Specifically in this experiment we will be dealing with optical data received by the brain through the optical nerve.

 

Step 1: Take a monkey or other such humanoid animal and remove 1 eye.

 

Step 2: Cut a small hole to the ocular nerve of the monkey's other eye.

 

Step 3: Attach a device that can monitor the EM frequency of the nerve.

 

Step 4: While monitoring the nerve have the monkey look at all the colors a computer can display.. Like 300 or 500 some colors.

 

Step 5: Analyze the data and look for patterns. (seems like there should be one.)

 

Step 6: Graph the pattern.

 

Step 7:Paint a Banana a non recognizable color so the monkey cannot recognize it. CONTROL have another monkey with no alteration also not recognize the bananna.

 

Step 8: Design a small device to transfer injected signals to the nerve

(its going to look like this: [Legend --- = nerve | = device \= wire]

(brain)--------------|------------------(eye)

\

 

Step 9: Block the monkey's signal coming from the eye.

 

Step 10: Put the banana in front of the monkey and see if he reaches out to get it.

 

Step 11: If the monkey doesn't grab it then unblock the signal. and see if he does.

 

Step 12: Put the monkey in a Pitch black room and setup an Infrared camera, and Outline the banana in infrared.

 

Step 13: inject the probable frequency to infrared and see if the monkey can see the banana. OR attach a camera whose output is conditioned to = that of the graph of stimulation frequencies. aka Camera sees green and its output (to the monkey) is as if the eye saw green.. but with lots of colors resulting in shapes n stuff.

 

Step 14 Observe the monkeys reaction.

[CharonY]

So, if you were to collect the frequency patterns from optical stimulation, you could find the probable frequency that the rod/cone would transmit into the nerve?

 

It is not the frequency, but more a matter of localization. I.e. which cells give the signals. The frequency basically corresponds intensity.

[Zolar V]

hmm interesting, is there anything i could look up to research that more?

[CharonY]

I would refer you to some neurobiology textbooks. There was an older, very well written one, but for some reasons I cannot recall the author. Hmm brain getting old.

 

 

edit: Geez can't believe I forgot his name. Eric Kandel.

Edited March 24, 2010 by CharonY

[Zolar V]

Thank you for your expertice and guidance in this area.

[ewmon]

Here's two articles on people being able to see ultraviolet:

 

Bird's-eye view

 

You don't have to come from another planet to see ultraviolet light

[Genecks]

In the eye of a mammal, lets say a human or a primate, is it the rods and stuff in the eye or the brain itself that cannot process infrared and ultraviolet electromagnetic frequencies?

 

I was talking to a professor about the possibility of getting a human rod/cone cell to express green fluorescent protein (GFP). From what I understand from his discussion and mine, UV light is what helps GFP luminesce. But the luminescence wouldn't occur in a human, because UV light can't pass through the lens. I believe that was the idea. This discussion came about from me wondering if a person would be blinded from having a functional and activated GFP in the cells of the eye.

 

A bee, however, may have problems with vision if GFP is expressed in those cone/rod cells.

 

With that in mind, I'm under the assumption that the human eye has not evolved to interpret UV rays, because they haven't been passing through all this time. Maybe there are slight deviations within the entire 6 billion people on the planet, as such, maybe there are a few people out there whom can actually process UV information. I wouldn't know of such people, though.

 

...So if you exchange a rod that adsorbs e.g. red most effectively and exchange it with one that reacts to UV your brain would interpret UV as red.

 

I think I see the logic in CharonY's response. I suspect there would have to be a way of exposing a primate or human to UV light and find a way to determine if the subject is experiencing some form of red sight.

Edited March 24, 2010 by Genecks

[Zolar V]

Genecks,

I am not really talking about having the eye absorb and interpret UV info. rather inject the info into the nerve. we get the probable "frequency" of the info by getting the same thing of known colors. however i must learn more about how nerves work before i can really continue in this thought process.

[Mr Skeptic]

Genecks,

I am not really talking about having the eye absorb and interpret UV info. rather inject the info into the nerve. we get the probable "frequency" of the info by getting the same thing of known colors. however i must learn more about how nerves work before i can really continue in this thought process.

 

Nerves transmit information in an all or nothing fashion. They don't transmit post-processed sensory information. It is pre-processed sensory information. Your brain will receive it and interpret it based on what nerve the information came from. There is no "color" transmission in nerves, but there are nerves connected to color-sensing cells. When the brain detects a signal from a nerve known to be carrying information from a red sensing cell, it will interpret that nerve impulse as red.

 

Close your eye and put a little pressure on your eye with your fingers. The pressure will cause some of the nerves in the eye to fire. Will you see pressure? No, you see weird light flashes.

[Zolar V]

"When the brain detects a signal from a nerve known to be carrying information from a red sensing cell, it will interpret that nerve impulse as red."

 

and here in we decipher the signal to color impulse and inject a signal with the probable properties of uv light or infrared.

[Mr Skeptic]

Well, you could try injecting a signal for ultraviolet directly into the data cable feeding into your computer screen. Do you think you can make it have extra colors by doing this?

 

If you have "information from nerve Z37 gives you the intensity of red light at such and such coordinates" then putting any signal on nerve Z37 will be interpreted as red at the same coordinates. The signal attributes will only change the intensity perceived. Do you mean to inject a signal directly into the brain? The brain has no understanding of ultraviolet, so it would have to learn to interpret whatever signal you are injecting. There's no signal anywhere that means ultraviolet; all the signals mean something else. You'd have to create a brain region for your ultraviolet signal before you could have an ultraviolet signal.

 

Your first idea was the correct one: it should be possible to add color cone cells to the retina that can detect additional colors. So long as you do it early enough, the brain should learn to accept the additional colors. It might even work at adulthood (if it doesn't your brain will get all sorts of confused by the new signal rather than seeing a new color). This may be possible to do with gene therapy. See this:

http://www.wired.com/wiredscience/2009/09/colortherapy/

 

Also, look up tetrachromats.

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In the eye of a mammal, lets say a human or a primate, is it the rods and stuff in the eye or the brain itself that cannot process infrared and ultraviolet electromagnetic frequencies?

 

Yes. Since the cells in the retina cannot convert these frequencies to nerve signals, your brain never receives signals from these colors and never attaches an interpretation to them. There are no infrared or ultraviolet or blue or green frequencies in the nervous system; only nerve impulses that are assumed to have a given meaning.

Edited March 25, 2010 by Mr Skeptic
Consecutive posts merged.

[ewmon]

Our perception of colors is based on the relative intensities of the signals generated by the eye’s S cones (short wavelength), M cones (medium wavelength) and L cones (long wavelength). For example, what we perceive as “blue” is mostly S signal with a little M signal and even less L signal; whereas “red” is mostly L signal with a little M signal and almost no S signal. It seems that “ultraviolet” would be perceived as all S signal and none of the others. Thus, perhaps the brain could be faked into perceiving ultraviolet if only the S cones or their nerves could be stimulated.

[Radical Edward]

In the eye of a mammal, lets say a human or a primate, is it the rods and stuff in the eye or the brain itself that cannot process infrared and ultraviolet electromagnetic frequencies?

 

precisely. This graph shows the response of the eye to different wavelengths of light in light situations (photopic response) and dim situations (scotopic response)

 

 

The eye has three sorts of opsins. These are slightly different proteins that adjust the wavelengths of light that a molecule known as cis-retinal can absorb. When this molecule absorbs a photon it changes shape and that results in the rod or cone firing a pulse (it's a little more complicated than that, but these are the basics.)

 

with the following curve showing the responses of the different opsins respectively:

 

 

We distinguish colour by the relative firing rates of cones with the different opsins in them (answering this). For example if we have 550nm light, the blue opsins barely respond at all, the green opsin a lot, and the red opsins a bit.. As you can see, these opsins simply do not absorb light in the UV and the IR.

 

an interesting aside here. the red and green opsins are on the X chromosome, so if a woman has a broken opsin, it is ok, because the opsin on the working chromosome can still let her distinguish the two colours. For men however, we only have one X chromosome, and so if an opsin is broken, we end up colorblind.

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I was talking to a professor about the possibility of getting a human rod/cone cell to express green fluorescent protein (GFP). From what I understand from his discussion and mine, UV light is what helps GFP luminesce. But the luminescence wouldn't occur in a human, because UV light can't pass through the lens. I believe that was the idea. This discussion came about from me wondering if a person would be blinded from having a functional and activated GFP in the cells of the eye.

yes that's right. The lens and the aqueous humor of the eyes are very poor transmitters of UV light.

A bee, however, may have problems with vision if GFP is expressed in those cone/rod cells.

 

With that in mind, I'm under the assumption that the human eye has not evolved to interpret UV rays, because they haven't been passing through all this time. Maybe there are slight deviations within the entire 6 billion people on the planet, as such, maybe there are a few people out there whom can actually process UV information. I wouldn't know of such people, though.

well bird eyes are tetrachromatic - they have another opsin

 

here's the equivalent curve to the one above for birds:

 

 

I think I see the logic in CharonY's response. I suspect there would have to be a way of exposing a primate or human to UV light and find a way to determine if the subject is experiencing some form of red sight.

 

well you can in principle do it purely by looking at the responses of the opsins themselves. The question then though is do we even have a channel to process additional colour information, or would any signals from spurious opsins just be lumped in with one of the other colour channels. There are thought to be human tetrachromats, although the new opsin lies between the green and blue.

Edited March 25, 2010 by Radical Edward
Consecutive posts merged.

[Mr Skeptic]

Our perception of colors is based on the relative intensities of the signals generated by the eye’s S cones (short wavelength), M cones (medium wavelength) and L cones (long wavelength). For example, what we perceive as “blue” is mostly S signal with a little M signal and even less L signal; whereas “red” is mostly L signal with a little M signal and almost no S signal. It seems that “ultraviolet” would be perceived as all S signal and none of the others. Thus, perhaps the brain could be faked into perceiving ultraviolet if only the S cones or their nerves could be stimulated.

 

Interesting. Now I want to know what that would look like.

[Zolar V]

Here's two articles on people being able to see ultraviolet:

 

Bird's-eye view

 

You don't have to come from another planet to see ultraviolet light

 

According to these articles, the brain is able to interpret UV light and we can see it.

 

"information from nerve Z37 gives you the intensity of red light at such and such coordinates"

Exactly,

Nerve Z37 gives you intensity x of red light, Nerve Z38 gives you intensity of y red light, Nerve Z37 and X37 give you x intensity of light... and so on.

 

My idea is to plot out all the nerve responses for the colors of light a human can percieve, then, follow the probablility that nerve Zxx would interpret the uv spectrum. and then inject that signal.

I suppose now that i know more about how information is transfered from the rods/cones to the brain through the nerve that such a word "signal" is not appropriate. Rather it should be "Stimulate(s)". Therefore i revise my previous statement;

"so, theoretically we could inject those frequencies into the ocular nerve, bypassing the rods and cones. Of course we would have to get the proper infrared and ultraviolet frequencies to inject. "

Rather we take this information gathered, and we follow the probability that X intensity of UV spectrum of light would stimulate X-Nerves Zxx.

[ewmon]

Mr Skeptic, I'd guess that UV would seem more purplish or an unknown shade of purple. I knew of an elderly lady who underwent cataract surgery and who complained afterwards that lots of things (like asphalt) were too purple. Maybe we can only guess at other shades of purple because most people have never seen them.

 

Radical Edward, Thank you. I didn't know that the L cones were stimulated in the blue region. I don't know if I learned that the different types of cones were supposedly simple "bandpass" filters or if I just fell into remembering them that way. So, maybe this explains why humans make color wheels where, illogically, the blue (short wavelength) wraps around to the red (long wavelength) with purple in between?

[pioneer]

The problem with UV is it can induce chemical reactions. Visible light defines less energy, allowing most chemicals to remain stable. If the eye could use UV, the receptors would have to be chemically tougher or would need to be constantly renewed due to UV damage. One might then lose some subtly in the visible range, due to the chemical armor.

 

If you look at our skin, if we filter out the UV, the skin stays softer when bathed only in visible light. If we add the UV back, our skin can turn leathery due to chemical reactions and may need to peel and regenerate. I assume evolution tried this and said, too much expense for small gain. There was no advantage.

[Zolar V]

The problem with UV is it can induce chemical reactions. Visible light defines less energy, allowing most chemicals to remain stable. If the eye could use UV, the receptors would have to be chemically tougher or would need to be constantly renewed due to UV damage. One might then lose some subtly in the visible range, due to the chemical armor.

 

If you look at our skin, if we filter out the UV, the skin stays softer when bathed only in visible light. If we add the UV back, our skin can turn leathery due to chemical reactions and may need to peel and regenerate. I assume evolution tried this and said, too much expense for small gain. There was no advantage.

 

Well that would be a valid point if i were thinking that we were to adjust the biological mechanism involved with perceiving light. However, I am talking about external mechanical gear taking in the UV/IR, and stimulating the associated nerves, mechanically, not biologically. I am not trying to delve into changing some properties of the human eye through whatever means necessary, I am discussing:

1) Whether or not the brain can interpret UV/IR information

and

2) Could we stimulate the right nerves to simulate our eye seeing parts of the EM spectrum

 

We have answered part 1, with these articles:

posted by ewmon

 

Here's two articles on people being able to see ultraviolet:

 

Bird's-eye view

You don't have to come from another planet to see ultraviolet light

Edited March 26, 2010 by Zolar V
Consecutive posts merged.

[Radical Edward]

it would just look like a very bright violet light of around 400nm (the same as when 400nm light fires off the blue cone only, but neither of the others). The brain generates the colours that you see from the different firing rates of the three types of cones.

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According to these articles, the brain is able to interpret UV light and we can see it.

 

 

Exactly,

Nerve Z37 gives you intensity x of red light, Nerve Z38 gives you intensity of y red light, Nerve Z37 and X37 give you x intensity of light... and so on.

 

My idea is to plot out all the nerve responses for the colors of light a human can percieve, then, follow the probablility that nerve Zxx would interpret the uv spectrum. and then inject that signal.

I suppose now that i know more about how information is transfered from the rods/cones to the brain through the nerve that such a word "signal" is not appropriate. Rather it should be "Stimulate(s)". Therefore i revise my previous statement;

"so, theoretically we could inject those frequencies into the ocular nerve, bypassing the rods and cones. Of course we would have to get the proper infrared and ultraviolet frequencies to inject. "

Rather we take this information gathered, and we follow the probability that X intensity of UV spectrum of light would stimulate X-Nerves Zxx.

 

all this has been done in the graphs I showed on the previous page. You should look up the CIE charts

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Mr Skeptic, I'd guess that UV would seem more purplish or an unknown shade of purple. I knew of an elderly lady who underwent cataract surgery and who complained afterwards that lots of things (like asphalt) were too purple. Maybe we can only guess at other shades of purple because most people have never seen them.

 

Radical Edward, Thank you. I didn't know that the L cones were stimulated in the blue region. I don't know if I learned that the different types of cones were supposedly simple "bandpass" filters or if I just fell into remembering them that way. So, maybe this explains why humans make color wheels where, illogically, the blue (short wavelength) wraps around to the red (long wavelength) with purple in between?

 

The colour wheels may look a bit strange, but there are good reasons for them. They are roughly based on this:

 

 

This chart shows the entire gamut of human vision; all the colours we can see (though being on a computer screen, the whole gamut is not actually representable, so you have to follow the numbers, Ill get into that a bit more in a moment.

 

I won't go into the detail of how this is produced, but it is based on the graphs I have posted previously. The very edge of the curved part of this chart though represents monochromatic light - all the colours that can be made from a single wavelength of light. The whole volume of the chart are all colours that are made from mixtures of monochromatic light. The straight line is made from mixtures of blue and red (the extent of our vision). As you can see, this pretty much follows the pattern of a typical color wheel.

 

 

Color wheels are also important in art. Say you are trying to shadow an area - you don't simply mix a bit of black in with the colours under shadow, you should take into account the illuminating colour, and then tint your shadow with the colour on the opposite side of the wheel.

 

Ok, Back to what I was saying about monitors though. Monitors as we know consist of three elements to each pixel, a red, green and blue element. As a rsult they are limited in what colours they can make. To show this on the colour gamut chart as I did earlier would show this:

 

 

As you can see, you basically get a triangle. Anything outside that triangle cannot be represented on that screen. Different sorts of screens have different triangles which is why the colours on older monitors can look rather odd today.