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When looking at a graph plotting "blue", "green" and "red" cones reponses to different wavelengths, you can see that any wavelength trigerring a response from green cones is also able to trigger a significant response from blue and red cones.

Excluding colorblindness, that must mean the green we're used to is the result from not only green cones activation, but also red and blue cones activation.

My question is: given the current knowledge of cones, the optical nerve and image processing in the brain (or anything else relevent of course), if my blue and red cones suddendly stopped reacting to light, would a 520nm wavelength light look "purer and greener" than it would in a normal situation, or would the brain interpret this as a different "unknown" color? Or perhaps might it not be able to interpet it at all until it forms new connections in order to understand it?

(While this is most likely a hard question to answer, perhaps knowledge about how the brain processes images is advanced enough to form a "likely" hypothesis, which is why I asked.)

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The genetic condition you are describing is called green cone monochromacy (GCM). This condition is exceedingly rare because it requires the dual inheritance of tritanopia (absence of blue retinal photoreceptors) and protanopia (absence of red retinal photoreceptors).1 Consequently, I can find very little information on the experience of people with GCM. In general, however, people with any type of monochromacy are considered completely colorblind. This is because color is perceived not by the excitation of specific cones but rather by the relative excitation of different cones and rods. So, a person with only one functional cone type can perceive the intensity of light but not the color.

If you're interested in the science of how the eyes and brain work together to process color, I suggest reading up on opponent process theory.


References

  1. Simunovic, M. Colour vision deficiency. Eye 24, 747–755 (2010).
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    $\begingroup$ I understand that, perhaps I phrased it wrong, what I meant is a more hypothetical (and possibly off-topic I am aware) where someone was trichromatic before switching to this situation, so that their brain would be wired for trichromatic vision and they would have memories of trichromatic vision to compare what they were now seeing to. While this is purely hypothetical (until very good prothetic retinas are invented I guess), I hoped current knowledge of the brain would have a crumb of hypothesis regarding the outcome. I will be checking that link, thanks. $\endgroup$
    – Uretki
    Sep 14 at 7:23
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    $\begingroup$ (cont.) My line of reasoning was that "green" cones would send signals using the preexisting circuitry that was built up from living as a trichromat, but the total received signal would be unique in that the brain would be receiving nothing from "blue" and "red" cones, something that never happened in a normal situation since green cone activation implied red and blue also activated. Even if it's not the cones themselves that encode color, the circuitry behind, in the brain, would still be there (at least for some time). $\endgroup$
    – Uretki
    Sep 14 at 7:26
  • $\begingroup$ @Uretki It was not that long ago when black-and-white monitors were in fact light-and-dark-green. ;) $\endgroup$ Sep 15 at 7:43
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Found a likely answer from the "See also" section of the link provided in acvill's answer. Turns out it seems that you can somewhat approach this situation by exploiting cone cell fatigue to lessen blue and red cone cells's response to green light. While this isn't exactly the situation described in the question (since I assume red and blue cone cells remain sensitive, just less), it seems to be pointing towards the "purer and greener" answer.

Link: https://en.wikipedia.org/wiki/Impossible_color#Chimerical_colors

Quote:

A chimerical color is an imaginary color that can be seen temporarily by looking steadily at a strong color until some of the cone cells become fatigued, temporarily changing their color sensitivities, and then looking at a markedly different color. The direct trichromatic description of vision cannot explain these colors, which can involve saturation signals outside the physical gamut imposed by the trichromatic model.

[...]

Likewise, staring at a bright magenta template may result in an impossibly highly saturated green afterimage.

So, I assume the result of deactivating red and blue cone cells and looking at a green light would be to see an exceptionally impossibly saturated green color.

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  • $\begingroup$ one can trick the brain to see only green for a short time,spend some time in a room brightly lit by grow lights(red and blue light with all the green removed)when you leave the room everything will look green until the brain adjusts back to normal lighting. $\endgroup$ Sep 15 at 9:54

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