Talk:Microtubule
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Removing Penrose/Moving

I had a conversation with a friend of mine this past weekend about this article, and because of the Penrose section he pointed out that this was a perfect example of why Wiki articles really can't be trusted for information beyond pop culture. Frankly that's the last straw for me since I feel like I've added evidence against Penrose as if I'm arguing with him when he really doesn't have any knowledge of microtubules. So I've decided that this information needs to be removed from this article. If anyone disagrees I'd like you to consider moving the section to the article about Penrose, since this theory is more about Penrose's personal philosophies about the nature of consciousness than about any actual scientific studies done on the topic. Kablamo2007 21:27, 26 February 2006 (UTC)

I've removed the section again after it was readded. While Roger Penrose's speculation on quantum consciousness are famous they are in no way authoritative, widely accepted, conform to the evidence, or have ever been empirically tested. In short, don't belong in an encyclopedia. For specifics see my post from a long time ago at the bottom of the talk. If you would like to include the topic in an article on Penrose or his theories then that is the appropriate place. Please, discuss this topic on the talk page before readding the section. 132.162.208.59 Kablamo2007 20:36, 18 October 2006 (UTC)

Perhaps some link to the Orch-OR article would be in order? Any discussion can take place there. I propose this because I wanted to review Penrose's theory and had some trouble locating the Orch-OR article: both this article and the Roger Penrose one didn't link there. I'll fix it for the Penrose one, but leave any modification of this page up to you guys and gals. --tijmz 14:59, 8 December 2006 (UTC)

Can something be said about the rebuttal of Max Tegmark's argument? I find it unusual that someone would post an isolated rebuttal of Hameroff's calculation, while neglecting what Hameroff has said about Tegmark's calculation. --DoYouKnow 3:00, 3 January 2007 (UTC)

I'm going to continue to work on this article, I don't research microtubules myself (which is good, because that might skew my vantage point for contributing), but I'm in biology/biochemistry... I separated a "structure" section from "organization" ... I'll be back to work on it more later... The so-called "theory of consciousness" has no business in this article... it should be removed entirely or reduced to a very small statement linking to a stub pertaining to it.IlliniWikipedian 17:34, 19 December 2005 (UTC)

a GDP-bound tubulin in the middle of a microtubule cannot spontaneously pop out.

This is incorrect. Microtubules are known to have the ability to subunit exchange within the polymer, but the occurence of these exchanges are infrequent enough to not endanger the stability of the polymer. -- user:Kablamo2007

Microtubules radiate from the centrosome.

The organization centres that microtubules come from are sometimes called centrosomes, but I think that's more often restricted to the centrioles. These only give rise to microtubules involved in mitotic division, and not those in flagella and axopodia, or those supporting the cell. There could be a connection, but some cells don't even have centrioles, e.g. plants. I'm going to err on the side of caution and remove it unless some better description is given. -- Josh

Actually where a centrosome is present it is the dominant site of microtubule nucleation and it is definitely fair to say that microtubules radiate from the centrosome. The centrosome organises a microtubule array in both mitosis and interphase in animal cells. AND the microtubules of the axoneme are nucleated and organised by the basal body, which is a modified form of the centrosome. The centrioles are a component of both the centrsome and the basal body.

Basal bodies are related to the centrosome, but in most books they aren't the same thing. The centrosome page flatly states that plants don't have centrosomes, and they do have microtubules. As such, making it look like all microtubules come from centrosomes is a mistake.

...however there is growing experimental evidence for a connection between quantum effects in microtubules and the mechanisms of consciousness.

Could we get a reference for this? It really sounds questionable to me. ---

move this to talk.

...however there is growing experimental evidence for a connection between quantum effects in microtubules and the mechanisms of consciousness.

At least mention what the evidence is.

Roadrunner 01:51, 3 Apr 2004 (UTC)

shrinkage vs retraction:

I changed "retraction" to "shrinkage". Depolymerizing microtubules do not usually retract. Depolymerization is the loss of monomers from one end, whereas retraction is a backward movement (or shifting/sliding) of the whole microtubule - an event which is not usually associated with depolymerization. In other words, microtubules can for example depolymerize and protrude at the same time, and it would appear, as if the microtubule would not change at all. However, all kinds of behavior (retraction vs. protrusion and depolymeriztion vs polymerization) can be disected and visualized by a technique called fluorescent speckle microscopy. Another often used expression to describe depolymerizing microtubules is the word "shortening"

This article is categorized under organelles, which microtubules are not. Should we change it? And, oh yeah, the consciousness thing is VERY questionable. --Delldot 22:48, 8 October 2005 (UTC)

I have no objection to removing this article from Category:Organelles. The "consciousness thing" is already marked as being on the scientific fringe. However, it is a famous proposal and I think it has a place in this article. Fringe ideas serve useful functions in science. There is nothing wrong with wikipedia showing that scientists can "think outside of the box" and that science does not break down when controversial ideas are discussed. Once in a while, a fringe idea even turns out to be correct. --JWSchmidt 01:29, 9 October 2005 (UTC)

Fringe is one thing. Penrose really knows nothing about how microtubules work. He started out with a conclusion in mind, that quantom effects could explain conciousness, and searched for something he could fit to his already made conclusion. That is psuedoscience to start with your conclusion in mind and fit the evidence to it. I stil think that the info should be left up with sufficient evidence that the strong scientific consensus is that it is dead wrong. Always good to openly debunk the talking heads for this kind of "science". I mean the fact that so many people take What the Bleep Do We Know!? seriously is reason enough to be worried for the future of science as a public endeavor in this country.Kablamo2007 06:10, 4 November 2005 (UTC)

What about Hameroff's reb

I agree that it is far better to explain why most scientists think microtubules are not central to consciousness than to ignore the issue. In my view, a hypothesis can only really become part of a pseudoscience if it is not subjected to critical analysis. The microtubule article should have some references for the "Microtubules and theory of consciousness" section. There should be discussion of the content of references that contain published microtubule-related quantum consciousness proposals and discussion of the content of articles that critically evaluate those microtubule-related quantum consciousness proposals. --JWSchmidt 13:20, 4 November 2005 (UTC)

Unfortunately I've never seen a concise single argument against Penrose published. Mostly I think this is because scientists in the field see it as immediately nonsense and see no reason to respond to something published as popular science. Penrose's idea has never been in the peer reviewed literature where they would feel compelled to respond (mostly because a reviewer would never let something like that through). I'll put all the reasons why I can see it doesn't work here and you decide if they belong in the article:

A Refutation of Penrose's Gödelian Case Against Artificial Intelligence (2000) http://citeseer.ist.psu.edu/320350.html This is watertight, and the fact that it destroys his central argument makes the rest of his musings unravel as irrelevant.

1. Microtubules are too large for quantum coherence. The inside of a microtuble is large enough to allow many water molecules and even some drugs such as the cancer medication taxol bind inside the microtubule. Right there is an obvious example of why microtubules don't produce conciousness. If quantum coherence inside the tubule could even occur then someone taking a drug like taxol should exhibit problems with cognitive functions of conscious.

2. While tubulin has two possible conformations, these conformations are not equally likely throught the microtubule. In fact the entirety of the tubule except the outside ring is one state while the outside ring is the other. Without the ability of the microtubule to click through these two states (the 1's and 0's of quantum computing) there is no basis for quantum consciousness.

3. Microtubules are present in all cells and in all eukaryotes. If they are the source of consciousness than why is yeast not conscious in the same sense that we are.

4. Finally, Penrose's argument is only based on the fact that he decided long before picking on the microtubule that consciousness must be a quantum phenomenon. While this may or may not be true, he has targeted the microtubule not out of real understanding of how it functions, but because it was the first thing that he could find that might fit his already formed theory. That's just bad science. Kablamo2007 07:57, 5 November 2005 (UTC)

The Penrose hypothesis, even though it is highly improbable (and most probably wrong) SHOULD be mentioned in the entry. Why? Because it exists (i.e. it was published and people can read it). An encyclopedia should cover as much content as possible. Someone who is reading Penrose's book could then consult Wikipedia, read the Microtubule entry, and learn that the scientific community has largely rejected Penrose's arguments. With references to authoritative work/opinions on the question. What's the point of not covering scientific work just because it is wrong? Then, shouldn't we remove coverage from famous hoaxes and scientific errors such as the Piltdown man, the Ptolemaic system or Lamarckism? This would be a dangerous path to follow. Hugo Dufort 05:43, 20 November 2006 (UTC)

And by the way, it IS possible to find refutations of Penrose's hypothesis coming from PhDs and experts. For instance, the following article has been published : http://psyche.cs.monash.edu.au/v2/psyche-2-03-klein.html So merely saying that Penrose's theory is "untouchable" by serious researchers is not a sufficient argument for totally ditching Penrose's theory out of the Wiki. It deserves to be criticized. -- Hugo Dufort 06:06, 20 November 2006 (UTC)

With reference to the citeseer link, the argument is not quite so clear cut. The authors argue that Penrose has not made his case. However, in the final paragraphs of the paper, the authors start to attack some proponents of strong AI (LaForte, Hayes and Ford) for demonstrating the same weaknesses as Penrose and failing to prove the consistency of Strong AI and Godel. In the final paragraph one of the two authors, Selmer Bringsjord, comes out of the closet as being 'in complete and utter agreement with Penrose that it is possible to drive the denial of Strong AI from Godelian facts'. Persephone19 21:27, 27 October 2007 (UTC)

MT and consciousness??

I strongly object putting a half-cooked theory into a encyclopedia. It has make its way to the textbook first. The molecular or even neuronal nature of consciousness is still a big controversy. Or even the definition of consciousness itself. And I found here stating that it came out of a nanotube? Objection!

11:11, 16 December 2005 (UTC)Jumpingrat

I'd agree with you, but JW Schmidt has said that because of the fame of Penrose that it should be addressed. I would like you to look at my earlier post in the talk about the reasons why it's a crackpot theory. I have yet to try to incorporate them into the article, because they're not something I can really site.... its just what I know is obvious from having undergraduate biology courses. If you could help by writing a good rebuttal paragraph and adding sources I think it would be nice. I do think this article needs to address and firmly rebut Penrose sense I've had a smart friend who's a neuroscience major interested in cognition come to me thinking this theory was "it" and myself having worked with a tubulin-like protein having to explain the reasons why penrose doesn't understand the microtubule. A well written paragraph explaining those points would be good for any readers of Penrose coming here for more information. Kablamo2007 04:34, 25 December 2005 (UTC)

As someone with a 10 year old BSc, but never done biology since high school, I got to this article when a non-scientific friend pointed me to the Hameroff site and asked me if it made sense to me. Being me, I looked him up here and one of the first links in the Hameroff article is to here. I learned 10x more from the explanation that Kablamo2007 wrote than I got from the main page. IOW, yes, lay people come here wondering if the science is credible. I think it would be appropriate to have a section about why microtubules aren't a QC thing. And I think it would be better to put it and mark it citation needed than to have nothing there. Ricky 13:10, 22 August 2006 (UTC)

Microtubules and quantum consciousness

Information is being regularly reverted about this subject, even though one editor actually acknowledges the subject is well known. The subject gets 66,900 Google hits from many proper sources, so there is no reason to continually remove the subject entirely. This will have to go to mediation if other parties continue their blanket removal of the subject. wikipediatrix 00:31, 19 October 2006 (UTC)

Neutrality of the quantum conciousness section

Okay, this section currently reads something like "Yeah, it exists, and it's completely wrong". There should be at least a small blurb about what the theory proposes, and any evidence that does in fact support it, if anyone feels qualified to do that.Nathanww 03:00, 22 February 2007 (UTC)

At this time there is no lab science in support of the theory. No microtubule researchers are interested in the topic at all since most don't see how it could work given the present knowledge about microtubules. The current "evidence" for the theory is just the theoretical requirements for quantum coherence which are addressed in the Orch-OR article and as of now there are theoriticians who have said they could never work for the time-scale, size/temperature of microtubules. Besides that fact is that microtubules don't work the way the theory assumes with two equally likely states... the states are not equally likely. I'm fine with the section being tagged... its my opinion that it should go, but it keeps coming back Kablamo2007 16:38, 28 February 2007 (UTC)

I'm just a biology student and I haven't really put any research into this matter, but the section about "Microtubules and consciousness" seems awfully misplaced and I don't understand what it's doing in this article. 130.243.248.239 15:42, 22 March 2007 (UTC)

Keep it, but be skeptical

I think the point is that the Penrose story is pretty much the only logically coherent story of consciousness that science has so far proposed -- sure it's way beyond the fringes and wacky and very very speculative -- but it is the /only/ story we have. Surely every living person on the planet is interested in what consciousness is, and unless they walk away from science altogether and sign up for some religious or new-age fiction then this is the best we currently have to offer. It's wacky, far-fetched, and not accepted by anyone, but its still currently the only, and therefore best, theory we have. —The preceding unsigned comment was added by 84.51.150.211 (talk) 08:53, 6 April 2007 (UTC).

I think you should mention the Penrose theory and link to another page where a more thorough examination of it can be made aside from this main article on MTs. I would do the same for any other notable past or present theory that relates or refers to the MTs.

Only theory? Whatever happened to intracellular electrical discharge triggering the release of chemicals from brain cells, that are sensed by other brain cells? Doesn't that count as such a theory, especially given the observation that drugs that alter, disrupt, or enhance this process produce observable, frequently repeatable changes in the emotional status of human beings? If microtubules were going to play any role at all, I'd be much more interested in hearing how they serve to alter the propagation of charge down the length of a neuron! 70.162.81.229 19:54, 24 July 2007 (UTC)

I just stumbled over this article looking for some info about microtubules and must say, that the Penrose-part is really irritating. I think you should mention that a theory, not supported by the scientific community exists and link to it, that should keep the conspiracy theory people from deleting it. (I'm not doing it myself as i'm no biochemist and do not really know much about this topic) As for presenting far-fetched, wacky theories as "science", it think that is a really bad idea and i would more likely associate that with new age-fiction than with science. --134.76.210.206 08:19, 25 July 2007 (UTC)

Penrose again

The microtubule/quantum consciousness thing has no place here, I've removed it. It is a wild speculation unsupported by anything. The statement that "the Penrose story is pretty much the only logically coherent story of consciousness that science has so far proposed" is absolutely not true (see the Wikipedia page on consciouscness for logically coherent theories of consciousness that are actually supported by evidence). We may as well say here that unicorn horns are made of microtubules. 137.132.243.141 —Preceding comment was added at 03:25, 17 October 2007 (UTC)

Why not make a link to quantum mind? --JWSchmidt 03:31, 17 October 2007 (UTC)

So, I just re-added the Penrose section. Not to be troublesome, I promise! Actually, I agree that it should NOT be part of this article. The theory is bunk, and at most should get a VERY SKEPTICAL article of its own, or maybe be resigned to a reference in the Penrose article. Before we delete it, I just want to make sure that most of the people CURRENTLY working on this page agree with the decision (since this seems to be the standard way to do things around here). --AaronM 02:46, 18 October 2007 (UTC)

There are dozens if not hundreds of fascinating, well-researched things microtubules ACTUALLY DO IN REALITY that are not part of the article (which contains very little on actual microtubule function). Including the most far-fetched and unsupported function for microtubules ever published (though never in a peer reviewed forum) is severely distorting. Having one piece of quackery claiming a function for which there is no evidence is ridiculous. It's like like having an article on radios that says "Radios make sound. Although many are skeptical, the government might be using them to read my mind."137.132.243.141 08:40, 18 October 2007 (UTC)

The Penrose/Hameroff take on microtubules lies well within the Wikipedia guidance for inclusion of non-mainstream of fringe theories. This says that the theory should be referenced extensively, in a serious manner and in mainstream publications. In particular debunking or disparaging comments, which are legion for this theory are in fact adequate to establish notability of the theory. The fact that many scientists reject or ridicule the theory is not really relevant in this context, so long as it is made clear that it is speculative. I think a few sentences giving a more detailed explanation of the processes proposed should be added. A paragraph on the various refutations could follow this, but in the interests of neutrality, attempts to reply to these refutations should not, as is common in the popular literature, be totaly ignored, for instance the Hagan, Tuszynski, Hameroff response to the better known Tegmark article on decoherence. Persephone19 21:04, 27 October 2007 (UTC)

The point is not whether it is allowable, the point is that it makes it a bad article. The entries should strive to accurately and concisely represent what is known and understood about microtubules. This entry is severely unbalanced, because it omits the many things microtubules DO do and gives space to something that a tiny number of people speculate, with no evidence, that they MIGHT do.24.252.32.54 22:54, 12 November 2007 (UTC)

The answer would seem to be to expand the main part of the article, which does seem skimpy for such an important component of cells. It goes without saying that the article should fully describe the known mechanism and function of the microtubules. However, I can't see that this precludes discussing speculative material. Given the widespread, if mainly critical coverage given to the Penrose'Hameroff proposal, many readers may access the article with the hope of getting more information on the theory. If anything it could do with fuller discussion, for instance the reasons for scepticism, as part of a more comprehensive article. Persephone19 11:18, 13 November 2007 (UTC)

Motor proteins and MAPS affecting MT dynamics

I think the article is a bit sparse on describing motor proteins interacting with MT, and should definitely give some space to microtubule associated proteins (MAPS) that can influence the dynamics of microtubules. Such MAPS can favour either a catastrophe or rescue state. Examples of these are numerous, such as XMAP215 (a MT 'polmymerase') and XKCM1 (a MT 'depolymerse'). In general, MT polymerases and depolymerases play important roles in enabling MT dynamics to be altered depending on the requirements of a particular cellular process. —Preceding unsigned comment added by 131.111.244.145 (talk) 08:12, 12 September 2007 (UTC)