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Add first post and images folder #27

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merged 4 commits into from May 16, 2015

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neuroamanda commented May 12, 2015

Ready for edits

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Replace this line with:


---
layout: post
title: Prism break, cuttlefish style

---

Replace this line with:


---
layout: post
title: Prism break, cuttlefish style

---
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RaoOfPhysics May 12, 2015

Relative links break in individual posts. :(

Replace image link with: ({{ site.url }}/images/2015-05-16-prism-break.jpg)

This SHOULD work!

Relative links break in individual posts. :(

Replace image link with: ({{ site.url }}/images/2015-05-16-prism-break.jpg)

This SHOULD work!

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
title: Prism break, cuttlefish style
---
_A suggested new biological color vision mechanism exploits optics_

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So many adjectives! I would trim, but your call.

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So many adjectives! I would trim, but your call.

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
From humans to mantis shrimp, the key to seeing in color is to compare. With at least two different types of wavelength-sensitive cells in the eye, you can start to distinguish different parts of the spectrum, and thus different colored objects in the environment. The more photoreceptor types you have, the more precisely you can interpret the incoming light, depending on how finely or evenly the [photoreceptor sensitivities are spaced on the spectrum](https://arthropoda.files.wordpress.com/2010/03/human-vs-mantis.jpg). Humans are trichromatic, with three kinds of cone cells well-tuned to the short, medium, and long wavelengths of our diurnal environment. The mantis shrimp has 16 photoreceptor types, suited to both its vibrant patchwork body coloring as well as its bright surroundings. The question then is, how many photoreceptors does the cuttlefish, [a squid-like underwater chameleon](https://www.youtube.com/watch?v=SfkhEm3LfvE), have?
Alas, the cuttlefish has but one type of photoreceptor. The instantaneous color and texture changes exhibited by this mollusk allow it to blend in seamlessly with any background it encounters, but it is effectively color blind, at least if color vision depends on comparison between cell types. [Some new research](http://dx.doi.org/10.1101/017756) suggests that "color blind" cephalopods like the cuttlefish _can_ sense chromatic information using an optical trick.

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"Some new research, however, suggests…"?

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"Some new research, however, suggests…"?

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
> _Eye of Australian giant cuttlefish (Sepia apama). [Photo](https://www.flickr.com/photos/rling/5101121081/in/photostream/) by Richard Ling / [CC BY-NC-ND 2.0](https://creativecommons.org/licenses/by-nc-nd/2.0/)_
Cuttlefish eyes make use of some interesting properties of light. Specifically, their pupils are unusual W-shaped slits that amplify chromatic aberration, the way light of different wavelengths bends slightly differently. Chromatic aberration explains purplish fringes sometimes seen in photographs: short wavelengths (blue light) get refracted or bent more than long wavelengths (red light)[^1]. Eliminating these "errors" is hard in any optical system, whether it's eyes or cameras. For the cuttlefish, this aberration signal actually provides valuable color information that is undetectable with only a single photoreceptor type.

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"slits, which amplify chromatic aberration or the way…"

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"slits, which amplify chromatic aberration or the way…"

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
Unlike the round human pupil, the squiggly pupil of the cuttlefish lets in light peripherally, off of the optical axis. This means the chromatic effects -- how differently the incoming wavelengths are focused -- are enhanced. Through its normal accommodation (focusing), the cuttlefish can _infer_ the colors of the environment, effectively using the distance it needs to focus as a clue to color.
For this system to work, the environment of the cuttlefish has to be full of cues to help it accommodate, like shadows and texture. Moreover, these features have be fairly sharply segregated spectrally (that is, neighboring objects need to be different and non-overlapping in hue), and fortunately for the cuttlefish they are. With its ersatz color vision mechanism the cuttlefish can't distinguish a broad flat field of a single color, though.

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color-vision? I really think it should be hyphenated here and above, but the decision is yours.

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color-vision? I really think it should be hyphenated here and above, but the decision is yours.

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
For this system to work, the environment of the cuttlefish has to be full of cues to help it accommodate, like shadows and texture. Moreover, these features have be fairly sharply segregated spectrally (that is, neighboring objects need to be different and non-overlapping in hue), and fortunately for the cuttlefish they are. With its ersatz color vision mechanism the cuttlefish can't distinguish a broad flat field of a single color, though.
Through computer simulations with different spectral inputs and pupil shapes, the researchers conclude that color information is in principle available to the cuttlefish. This may be the elusive mechanism to explain how cuttlefish make the spectral discriminations that are compatible with their vivid displays and camouflage abilities. New kinds of color vision tests, ones that don't presuppose opponency or comparison mechanisms, are needed to experimentally determine the color sensitivity of cuttlefish vision; according to the simulations, the cuttlefish eye can distinguish colors unambiguously, as long as objects are at least 0.75 meters away. This kind of analysis of annular pupils also raises the question of how other species, such as certain dolphins, might make use of the cuttlefish's optical trick for color discrimination.

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Link to definition of "opponency"?

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Link to definition of "opponency"?

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
Through computer simulations with different spectral inputs and pupil shapes, the researchers conclude that color information is in principle available to the cuttlefish. This may be the elusive mechanism to explain how cuttlefish make the spectral discriminations that are compatible with their vivid displays and camouflage abilities. New kinds of color vision tests, ones that don't presuppose opponency or comparison mechanisms, are needed to experimentally determine the color sensitivity of cuttlefish vision; according to the simulations, the cuttlefish eye can distinguish colors unambiguously, as long as objects are at least 0.75 meters away. This kind of analysis of annular pupils also raises the question of how other species, such as certain dolphins, might make use of the cuttlefish's optical trick for color discrimination.
Playing off sensitivity in one domain (color) against another (focal length) is an ingenious adaptation to compensate for apparent sensory deficits. Studying these adaptations, such as the [diversity of pupil shapes in nature](http://jov.arvojournals.org/article.aspx?articleid=2142714), demonstrates that the eye has evolved to be exquisitely tuned to its surroundings.

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"such as" seems a bit off. Do you mean to say, "as seen in the diversity of pupil shapes"?

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"such as" seems a bit off. Do you mean to say, "as seen in the diversity of pupil shapes"?

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@neuroamanda: Reads very well! Some small comments inline, above. Implement as you see fit. :)

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RaoOfPhysics commented May 13, 2015

@neuroamanda: Reads very well! Some small comments inline, above. Implement as you see fit. :)

More edits from AR
Incorporated some suggested changes
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RaoOfPhysics May 14, 2015

No hyphens. Sigh. :P

No hyphens. Sigh. :P

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
_A suggested biological color vision mechanism exploits optics_
From humans to mantis shrimp, the key to seeing in color is to compare. With at least two different types of wavelength-sensitive cells in the eye, you can start to distinguish different parts of the spectrum, and thus different colored objects in the environment. The more photoreceptor types you have, the more precisely you can interpret the incoming light, depending on how finely or evenly the [photoreceptor sensitivities are spaced on the spectrum](https://arthropoda.files.wordpress.com/2010/03/human-vs-mantis.jpg). Humans are trichromatic, with three kinds of cone cells well-tuned to the short, medium, and long wavelengths of our diurnal environment. The mantis shrimp has 16 photoreceptor types, suited to both its vibrant patchwork body coloring as well as its bright surroundings. The question then is, how many photoreceptors does the cuttlefish, [a squid-like underwater chameleon](https://www.youtube.com/watch?v=SfkhEm3LfvE), have?

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Picking nits here, but there is a subtle difference between "different colored objects" and "different-colored objects".

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Picking nits here, but there is a subtle difference between "different colored objects" and "different-colored objects".

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
For this system to work, the environment of the cuttlefish has to be full of cues to help it accommodate, like shadows and texture. Moreover, these features have be fairly sharply segregated spectrally (that is, neighboring objects need to be different and non-overlapping in hue), and fortunately for the cuttlefish they are. With its ersatz color vision mechanism the cuttlefish can't distinguish a broad flat field of a single color, though.
Through computer simulations with different spectral inputs and pupil shapes, the researchers conclude that color information is in principle available to the cuttlefish. This may be the elusive mechanism to explain how cuttlefish make the spectral discriminations that are compatible with their vivid displays and camouflage abilities. New kinds of color vision tests, ones that don't presuppose [opponency](http://en.wikipedia.org/wiki/Opponent_process) or comparison mechanisms, are needed to experimentally determine the color sensitivity of cuttlefish vision; according to the simulations, the cuttlefish eye can distinguish colors unambiguously, as long as objects are at least 0.75 meters away. This kind of analysis of annular pupils also raises the question of how other species, such as certain dolphins, might make use of the cuttlefish's optical trick for color discrimination.

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Make use of the cuttlefish's optical trick or make use of optical tricks similar to that of the cuttlefish?

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Make use of the cuttlefish's optical trick or make use of optical tricks similar to that of the cuttlefish?

Show outdated Hide outdated _posts/2015-05-16-prism-break.md
Through computer simulations with different spectral inputs and pupil shapes, the researchers conclude that color information is in principle available to the cuttlefish. This may be the elusive mechanism to explain how cuttlefish make the spectral discriminations that are compatible with their vivid displays and camouflage abilities. New kinds of color vision tests, ones that don't presuppose [opponency](http://en.wikipedia.org/wiki/Opponent_process) or comparison mechanisms, are needed to experimentally determine the color sensitivity of cuttlefish vision; according to the simulations, the cuttlefish eye can distinguish colors unambiguously, as long as objects are at least 0.75 meters away. This kind of analysis of annular pupils also raises the question of how other species, such as certain dolphins, might make use of the cuttlefish's optical trick for color discrimination.
Playing off sensitivity in one domain (color) against another (focal length) is an ingenious adaptation to compensate for apparent sensory deficits. Studying these adaptations, for example the [diversity of pupil shapes in nature](http://jov.arvojournals.org/article.aspx?articleid=2142714), demonstrates that the eye has evolved to be exquisitely tuned to its surroundings.

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RaoOfPhysics May 15, 2015

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Not sure "ingenious" is the appropriate adjective: it seems to imply some "intelligence" at play…

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RaoOfPhysics May 15, 2015

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Not sure "ingenious" is the appropriate adjective: it seems to imply some "intelligence" at play…

neuroamanda added a commit that referenced this pull request May 16, 2015

Merge pull request #27 from neuroamanda/add-article
All edits for first post done

@neuroamanda neuroamanda merged commit 2a9856f into apostilb:master May 16, 2015

@neuroamanda neuroamanda deleted the neuroamanda:add-article branch May 16, 2015

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