Talk:Photoreceptor cell

Poor style overemphasizing new discovery
Overuse of words like "novel" (5 times), and praise like "highly significant", "pioneering", "exciting" eg: "It is important to note that older textbooks will not contain yet the most exciting discovery in the field of human photoreception and vision. " ... "These non-rod non-cone photoreceptors in general are discussed later below." are bloated and detract from the quality of the article. Also many unnecessary dates ("in 2007", "2008" etc) in narrative style. The section Ganglion cell (non-rod non-cone) photoreceptors may need to be moved to it's own article if it is so significant —Preceding unsigned comment added by Theshadow27 (talk • contribs) 03:11, 20 March 2009 (UTC)

1st reply: i definitely agree with this oppinion. shortly after starting to read the intro i wasn't sure anymore if it was a general article on PRCells or this ganglion type cell that was recently found to be able to detect some light as well. —Preceding unsigned comment added by 81.107.43.84 (talk) 23:07, 21 April 2009 (UTC)

Error under Histology?
The histology section states, "Closest to the visual field (and farthest from the brain) is the axon terminal," and, "Finally, closest to the brain (and farthest from the field of view) is the outer segment, the part of the photoreceptor that absorbs light." I'm not an expert in this subject, but the positions of these parts relative to the brain seem to be reversed. —Preceding unsigned comment added by 76.182.91.31 (talk) 17:57, 15 June 2008 (UTC)

Actually, the article's statement is CORRECT. Though it seems very counterintuitive, the rods and cones are at the most posterior (towards the brain) end of the retina, and they send their signals away from the brain, because the bipolar, amacrine, and horizontal cells are anterior (towards the cornea) of the rods and cones, and the retinal ganglion cells are anterior to bipolar, amacrine, and horizontal cells. It's weird, but I believe the article discusses the advantages of this. My reference (sorry it isn't available online) is: Perception (Fifth edition), by Randolph Blake and Robert Sekuler (2006). It's a university textbook about psychophysics and the study of perception, with a very large amount of information about vision and the visual system. Miroku Sanna (talk) 18:06, 31 March 2009 (UTC)

I added a link to the retina article, hopefully clarifying this issue (Horuskemwer (talk) 16:54, 26 March 2011 (UTC))

Proposed merge
The proposed merge with Photoreceptor cell is being discussed at Talk:Photoreceptor cell.--Srleffler 04:27, 27 June 2006 (UTC)

Signal transduction pathway
I think "signal transduction pathway" would be easier to read if each number did not rephrase in parenthesis what it just stated. —The preceding unsigned comment was added by Tjerman (talk • contribs) 10:25, 14 September 2006 (UTC).
 * There was recently a merge with another article that contained virtually the same information. This section still needs to be cleaned-up. Feel free to lend a hand if you have the time! -AED 15:52, 14 September 2006 (UTC)

More than 2 types of photoreceptors in humans!
Hi,

There are more than 2 types (rods and cones) of photoreceptors in humans. The 3rd is the photoreceptive ganglion cells in the Ganglion Cell layer. See any Foster paper from 2003.

Thanks I've just finished the reading for my clocks essay and it's quite rewarding to correct everybody who, evidently hasn't!


 * ) —The preceding unsigned comment was added by 144.82.106.47 (talk) 19:11, 11 January 2007 (UTC).

Invertebrate Photoreceptors
Not sure if this is the right place, but the lack of an invertebrate photoreceptor article detailing the differences indicated in this article seems...not very good? Unfortunately I don't have any expertise in this area--maybe the mention of a few references or external links would be enough to rectify the omission. I came here looking for some information on the operation of eyespots in freshwater planaria, and seem to have encountered a dead end.

128.189.240.255 06:05, 15 February 2007 (UTC)


 * I have just encountered the same problem 9 years later (!) looking for octopus photoreceptors. I've been doing a bit of research but I wonder if someone with more knowledge can tell me whether the rhabdom is analogous to the rods and cones, i.e. is the rhabdom a photosensitive cell? DrChrissy (talk) 20:27, 30 April 2016 (UTC)

Disambiguation needed?
As a molecular biologist, the way I think about photoreceptors is in a molecular sense, e.g. rhodopsin, phytochrome, and cryptochrome, and not as cells. I think this page would need to be disambiguated for that meaning or expanded by a section on the molecular meaning of photoreceptor. Some plant photoreceptors, e.g. phototropin, actually link here which makes no sense at all since plants don't have neurons or a retina. I can see how "photoreceptor" seemed to be a simpler term than "photoreceptor cell", but it is also ambiguous for photoreceptor molecules (which exist in many organisms all the way from bacteria to plants) and the page currently doesn't reflect that. - tameeria 16:15, 5 March 2007 (UTC)

I found that besides "photoreceptor protein" or "photoreceptor molecule", some pages also use the term meaning "photoreceptor organ" (e.g. ocellus, eyespot). So with three distinct biological meanings (molecular, cellular, organ), I think there really needs to be some sort of disambiguation here. Incidentally, redirecting photoreceptors, microbial here makes as little sense as redirecting the plant photoreceptors to this page. - tameeria 00:33, 6 March 2007 (UTC)

I've added a disambiguation page. However, I've also noticed that this page started out talking about photoreceptors in a molecular sense and many links here reflect that meaning (e.g. photopigment, photoreceptors, microbial etc. It has changed significantly from those earlier versions and now the original content is lost as it talks exclusively about photoreceptor cells at the expense of photoreceptor molecules, rendering many of those links nonsensical. I would suggest moving this page back to photoreceptor cell to reduce confusion and use this page to give an introduction to molecular photoreceptors instead, as originally intended when the page was created. - tameeria 21:10, 16 March 2007 (UTC)

Requested move
These two pages were merged a while ago, but only after the "photoreceptor" page underwent a change in topic. Originally, it was about "photoreceptor proteins" instead of "photoreceptor cells" (see here). It was at some point disambiguated for "photoreceptor cell" (see here) and then the protein content was dropped completely and the article evolved basically into a content fork of "photoreceptor cell" (see here) and consequently was merged with that page. As a result, many incoming links created over the course of the page's existence (e.g. plant and bacterial photoreceptors) now don't make sense at all (plants and bacteria don't have neurons, obviously).

I would suggest moving the current page back to "Photoreceptor cell" and replacing it with the content of Photoreceptor (disambiguation) as incoming links can mean a number of things besides photoreceptor neurons (e.g. photoreceptor molecules, organelles, organs etc.). I would guess that "photoreceptor cell" and "photoreceptor protein" are at least equally likely meanings for the term, being the "predominant" meaning only in their respective fields (neurology/cell biology versus biochemistry/molecular biology). Therefore, I think "photoreceptor" should be a disambiguation page pointing to these different meanings.

If anyone has comments or concerns about this proposed move, please feel free to discuss them here. - tameeria 19:41, 17 March 2007 (UTC)


 * Moved. In order to maintain the edit history of the pre-merge "photoreceptor cell", I have moved it into the talk namespace at Talk:Photoreceptor cell/July 2006, and its talk to Talk:Photoreceptor cell/July 2006 talk. --Stemonitis 11:46, 23 March 2007 (UTC)

Local Graded Potential
I created a new page for Localized graded potentials and I am going to place a link to it under see also. Hope nobody objects. Paskari 18:44, 27 March 2007 (UTC)

Problem with absorbance curves
(I posted the same remarks on the image page, trying to find someone who knows about these)

I replaced these curves in the English wikipedia article on cone cells, because they have several problems:


 * 1. They are unsourced, so can't be verified.
 * 2. They show curves that are not even quite unimodal, unlike anything in the literture.
 * 3. The curves don't fall off as much as expected, esp. at 400 nm, so are useless as in indication of visual sensitivity
 * 4. It's really unclear whether these "asborbances" are supposed to like "responsivities". They don't look it.  Maybe absorbances are supposed to be different from responsivities, and if so we should say so, but what I've seen suggests they should be the same.

Does anyone know where they came from, so we can check and adjust them, and say more clearly what they represent? Dicklyon 16:25, 30 September 2007 (UTC)

Almost three years passed.... no response.... I think these curves must be deleted because of nonsense they cause. I suppose, somebody confused these curves with the curves that display the absorbance of pigments or something. Unfortunately, this plot travels through the borders: e.g. it could be found in russian wikipedia - without any explanations (exactly like it is in english). I tried to find the answer here, so, english-speaking people also do not know where that came from. 195.209.74.224 (talk) 07:54, 6 April 2010 (UTC)

These curves certainly should not be deleted and are not nonsense, they can be found in any textbook. They are not supposed to be unimodal, they are not statistical distributions, but the result of point measurements of how much cone activity is produced by stimulation from a single wavelength source at fixed intensity. Surely there are better visual depictions of the graph, but this one seems adequate. I rewrote the discussion of how to interpret them in an attempt to clear up meaning of the graph. (Horuskemwer (talk) 17:00, 26 March 2011 (UTC))

Further clarification: I looked into it and the most detailed sources I've seen give absorbance curves that are inferred from experiments involving the degree of responsiveness of the cell when flashed with fixed intensity light at different wavelengths. This info dates from 1995, though (I added a reference), so if a method for measuring absorbances directly has appeared since then, someone should put a reference to that in. (Horuskemwer (talk) 18:12, 26 March 2011 (UTC))


 * Like the commenter from a few years ago, I'm puzzled by the appearance of the absorbances graph in the section "Humans". I'm no expert, but having said that, I've never seen the graph drawn like that -- I've always seen it as drawn here on the cone cells page: that is, with the left endpoints (not just the right endpoints) at a height of zero, and as the above commenter said, unimodal (not because of anything to do with a statistical distribution, but because that's the way the cells respond -- less response the farther the frequency is from the peak response frequency, descending monotonically to zero response). The graph in this article has a source given, and it appears on p. 505 of that source; but look at the graph on p. 509 of that source -- it fits with what I'm saying about monotonicity on each side of the peak (though it doesn't follow the curves all the way down to zero).  Should that graph (or the one in the cone cell article) be the graph that we use in this article? I think the one in the cone cell article is very clear and typical, but it doesn't have a curve for the rods. Duoduoduo (talk) 01:29, 1 June 2011 (UTC)

Ganglion cell part too long!
I think this part has too much information. At least more than should be expected from the wikipedia. It wasn´t written in a neutral enough fashion, IMHO, so I edited it a bit. Citotoxico (talk) 02:51, 23 May 2008 (UTC)

MK: I agree with this. especially in the introduction it should not take that much space.

I rephrased the first paragraph of this section, in an attempt to give it a more encyclopedic style. To me, this short paragraph would be enough to cover the topic of intrinsically photosensitive Retinal Ganglion Cells (ipRGC) in this article. Readers with special interest in this topic should be directed to the article dedicated to ipRGC for the details. I did not remove the rest of the section myself, as too many changes and deletions in one step by one person might be perceived as vandalism, resulting in global reverting of the changes and thus hindering progress. Hopefully this first step will encourage others to pursue the clean-up work in this section. Lessato (talk) 11:55, 24 April 2009 (UTC)


 * I worked on the 3rd paragraph, up to 'citation needed', but it still needs a lot more work. There's no reason to include researches names in this section, that info should go in an article on "the discovery of ipRGC" or a page on the researcher. This section is still filled with narrative and does not meet style requirementsTheshadow27 (talk) 15:55, 27 August 2009 (UTC)

Merging Cone Cell and Rod Cell to Photoreceptor Cell
Cone Cell and Rod cell articles have very similar content. It might be a good idea to merge them together. Fangfufu (talk) 04:24, 15 December 2008 (UTC)

Bad idea. Then you will have to sort the material for the two different cell types. Photoreceptor Cell can point to rod and cone cell in its links area, thus each can be fully developed irregardless of the other. Radzewicz (talk) 21:07, 31 January 2009 (UTC)

I came to find out if rods or cones were the B&W ones. Paragraph 3 talks about "that's why you don't see color at night", without the article getting to explaining cones vs. rods first, and is thus confusing.

Suggest leading off with "There are many types of photoreceptor cells." then immediately jump into rods and cones. Finish up the intro with brief listing of other types. — Preceding unsigned comment added by 67.149.59.83 (talk) 13:28, 8 November 2012 (UTC)
 * I also have been unclear as to which of the two are for color vision, and the sentence now present, "In humans, there are three different types of cone cell, distinguished by their pattern of response to different wavelengths of light." now clears it up for me: CONES ARE FOR COLOR. A useful mnemonic! UnderEducatedGeezer (talk) 00:53, 13 December 2018 (UTC)

Orphaned references in Photoreceptor cell
I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of Photoreceptor cell's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "Kandel": From Cone cell:  From Rod cell: Kandel E.R., Schwartz, J.H., Jessell, T.M. (2000). Principles of Neural Science, 4th ed., pp.507-513. McGraw-Hill, New York.  

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT ⚡ 14:26, 1 February 2009 (UTC)
 * Done. - Hordaland (talk) 12:03, 9 March 2009 (UTC)

Do rods detect color at all?
I was thought that rods cannot detect color at all and only produce white sensation. But this article says they "do not detect color well".--MathFacts (talk) 09:31, 14 December 2009 (UTC)


 * It is an odd way to put it; but it would also be odd to say they don't detect color at all. Cones don't detect color, either; color comes from comparing the responses of several cone types, and rods do participate in that as well, to some extent.  Probably we should look at some sources for a better way to put it.  Dicklyon (talk) 23:30, 14 December 2009 (UTC)

The way it is written is how my college bio-psychology class handles it. I don't think this is a problem at all. Indolering (talk) 20:16, 12 December 2010 (UTC)

I have tried to clarify this point by distinguishing between color experience and light receptivity. Strictly speaking, none of the photoreceptor cells detect "color" directly - rather, color is calculated from comparing their responses. The point about the role (or not) of rods in color experience is a good one, but I think controversial. I suggest only discussing the role of cones in color vision (as their role in this is better understood) unless an expert on this topic comes along. (Horuskemwer (talk) 17:07, 26 March 2011 (UTC))

'Burn in' color phenomena
Is there a term for the occurrence when one stares at a light or a bright surface and then looks away and/or closes ones eyes; of that magenta shadow of the bright object as an initial color splash, slowly fading into its inverse of a mint green after-glow? 74.209.54.156 (talk) 08:23, 17 July 2011 (UTC)

Dark current
The "dark current" hyperlink in the section of the same name directs the reader to a disambiguation page with three options, the only relevant one being "Dark current (biochemistry)" which redirects the user to this page. Until an article dedicated to the topic is created, I suggest that the hyperlink be removed in order to avoid this kind of circular behavior. 128.135.6.108 (talk) 04:37, 24 January 2012 (UTC)
 * Done.  Thanks.  --Hordaland (talk) 06:55, 24 January 2012 (UTC)

Fig 1B
Fig 1B direction of light is wrong, and RPE layer mislabeled. see http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/ 129.237.101.199 (talk) 17:23, 6 September 2014 (UTC) 129.237.101.199 (talk) 17:25, 6 September 2014 (UTC)


 * Thank you for pointing this out.
 * We do agree that the direction of light in 1A is correct.
 * I will (try to) contact the person who uploaded the image. I intend to suggest that an image-file with just the 1A part of the image we have now, would do, IMO.
 * --Hordaland (talk) 04:03, 7 September 2014 (UTC)
 * Yes, I see the issue, the bipolar cells are not correctly labeled and the entire image is flipped. I uploaded this image from a CC-BY book a number of months ago, I will see if they have corrected the image in their newer edition. I suggest we use 1A for the time being. -- CFCF  🍌 (email) 13:17, 7 September 2014 (UTC)
 * It isn't updated, so it seems I will have to update the image myself–and it might be a little while until I have time to do that. -- CFCF  🍌 (email) 13:25, 7 September 2014 (UTC)

So, I rotated the image and added captions for some other structures. Please do comment on the new image. -- CFCF  🍌 (email) 13:53, 7 September 2014 (UTC)

leftover "in addition"
Certain owls, such as the tawny owl, have a tremendous number of rods in their retinae. In addition, there are about 2.4 million to 3 million ganglion cells in the human visual system, 1 to 2% of them photosensitive.

I don't understand this transition. Perhaps the phrase "in addition" is leftover from some long-ago version. &mdash; MaxEnt 12:21, 27 February 2018 (UTC)
 * I don't think it was really meant as a transition at all, though it does seem to clearly read that way, but was rather more likely a matter of a slightly poor choice of words, intending to be a continuation from the initial sentence in that section (about rods & cones in humans). I changed the wording of the second quoted sentence to, "In the human visual system, in addition to the photosensitive rods & cones, there are about 2.4 million to 3 million ganglion cells, with 1 to 2% of them being photosensitive.", to attempt to clarify. UnderEducatedGeezer (talk) 01:58, 13 December 2018 (UTC)

Image of photoreceptors cell and direction of light is backwards
Change image on the bottom, invert light direction Npapadonis (talk) 00:53, 29 May 2022 (UTC)

S M L vague
(Disclaimer: I’m a Web surfer, not a scientist.)

The Photosensitivity section says “Humans have three classes of cones (L, M, S) that each differ in spectral sensitivity and 'prefer' photons of different wavelengths (see graph)”.

However, the referenced graph (Normalized human photoreceptor absorbances) has no mention at all of those L M S classes and, instead, identifies the curves (in the legend) as ‘Blue cones’, ‘Green cones’ and ‘Red cones’.

Are they the same thing? If so, perhaps either the graph should be revised, or something like “Those ‘preferred’ wavelengths of S-, M-, and L-cones are commonly associated with the colours blue, green, and red, respectively” could be added to the article text.

Addendum: I just looked at the code for that section on the article’s Edit page and see that the file link to an earlier version of the graph has been retained (in a code comment, so that the image is no longer displayed).

That obsolete graph does give both L/M/S designations (directly labeled on the curves) and the colour names (auxiliary tags below the wavelength axis identify the spectral ranges corresponding to ‘violet’ through ‘red’), which confirms that they are directly related. Thus, the curves could appropriately be labeled L/M/S. Indeed, that may even be the technically preferred terminology, as I suspect that “Blue[/Green/Red] cones” (the labels in the current graph) might be a colloquial way to refer to them. (The older graph is not as pretty, but I do prefer that it associates colours with ranges of the spectrum, rather than with curves that span its entire width.) Starling2001 (talk) 17:17, 28 June 2023 (UTC)