Talk:Hippocampus

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You may want to revise the section about the hippocampus being phylogenically old. In fact, all of cortex is phylogenically recent. The hippocampus develops from telencephalic tissue, the most phylogenically recent section of neural tissue. The hippocampus is phylogenically "older" than neocortex, but midbrain and hindbrain regions (pons, medulla, etc) likely evolved much earlier.

I think the phylogenetic history of the hippocampus should be extended and moved to its own section. "Emergence from the archipallium" is a bit technical. Maybe this needs some introductory explanation. Washington irving 10:15, 26 Feb 2004 (UTC)

Maybe, we should use more accessible phrases such as "more recent in evolutionary terms" rather than "phylogenetically younger".

The component parts of the hippocampus need to be described. I can't find any references to presubiculum, subiculum, prosubiculum, or the CA segments.

Contents

[edit] Hippocampus and penis size

Does anyone have any cites for the claim about the relationship between hippocampus and penis length? If so it should be expanded and made more clear if not we should delete the reference to this somewhat dubious sounding claim.

[edit] Hippocampus

Is there any physical link between the Hippocampus and the Hypothalamus? That is, are they or aren't they indepedent of one another? --Tothebarricades.tk 03:56, May 12, 2005 (UTC)

There is a physical link between both. There are a number of fiber track that run through the lateral hypothalamus to the fornix and into the hippocampus. This physical data has also been shown behavioraly through fear conditioning studies. Goferwiki 10:18, 16 Jun 2005 (UTC)

[edit] Anatomy note

Is it sure that the hippo. is part of cortex or subcortex? Anyone of you could answer to this (trivial) question, please? --Eletto

The CA fields, dentate gyrus, and subiculum are classified as allocortex. The presubiculum, parasubiculum, and entorhinal cortex are classified as periallocortex. Much of the rest of the corical mantle is isocortex (there are a few other regions, like parts of orbitofrontal and piriform that are not isocortical, as I recall). 128.197.81.223 20:50, 13 July 2006 (UTC)
Oops, that was me. I wasn't logged in apparently. Digfarenough 20:51, 13 July 2006 (UTC)

Nice job, indeed. Thanks a lot. --Eletto 03:55, 20 September 2006 (UTC)


I added a section on some details of hippocampal anatomy, but I'm not sure how much detail should be included as this is an encyclopedia, not a neuroscience textbook. Anyone know what the limit is? I could write much more about electrophysiology of hippocampus as well as current models about its function and anatomy and so forth and can provide good references for both the new information and for information already mentioned in the article... Digfarenough 02:24, 17 August 2005 (UTC)

Nice work, Digfarenough. My philosophy on this is to write as much as I can. Another user and I are both heavily reworking cerebellum right now. Head over there and you will see the amount of detail we've included. Be as thorough as you can! Semiconscious (talk · home) 05:45, 17 August 2005 (UTC)

[edit] Very big POV problem

I came to this page looking for information on the hippocampus, as in the creature from Greek mythology, and was very disappointed to find an entire article dedicated wholly to one rather obscure use of the word. While the usage in medicine/anatomy is certainly important, it has absolutely nothing to do with what most people understand a hippocampus to be. The only information on this page relating to the mythic hippocampus is "In Greek mythology, the hippocampus ("horse-like sea monster") was a mythical monster, half horse, half sea-monster. One of them pulled Poseidon's chariot. It looked like a horse with the rear part resembling a fish or dolphin." This page gives the overall impression that the medical usage is the more important one and therefore deserves top-billing, while in truth neither usage is "more important" than the other, and the mythological usage is doubtless by far the most common outside of medical circles.

Either the medical/anatomical usage needs to be moved to its own page (as the mythological usage dramatically overshadows the medical usage), or all uses need to be moved to their own pages, leaving this page as a disambiguation. --Corvun 11:42, August 22, 2005 (UTC)

  • Admittedly I'm a neuroscientist, so I am biased, but I'm sure your claim that "the mythological usage dramatically overshadows the medical usage". In Greek mythology, hippocampus is a minor character, whereas in the brain the hippocampus is one of the most important structures about which every student in biology, psychology, etc. knows, as it is what is responsible for formation of memories. A quick Google check shows that the words "hippocampus brain" return about 675,000 hits, whereas "hippocampus Greek" gives only about 22,400 and "hippocampus mythology" only about 5,830. If you can find evidence that this 30:1 ratio of usage is incorrect, then I'd love to see it.

Anyway, the English transliteration for the Greek mythological creature is "hippocamp", correct? So shouldn't that page include the piece about the Greek mythology version, and not "hippocampus"? Semiconscious (talk · home) 15:25, 22 August 2005 (UTC)

I'm aware of the importance of the hippocampus in medicine/anatomy (including psychology). I may not be a neuroscientist, but I took biology and psychology classes in school and am therefore aware of the important role that the hippocampus plays. But aside from those people who actually end up pursuing a career in medicine, I sincerely doubt that anyone first thinks of this usage when hearing the word "hippocampus". All a quick Google search shows is that there are more articles on the part of the brain than on the mythological creature, which is expected since an extinct mythology is finite and experiences few if any new additions whereas the field of medicine is in constant, almost violent flux.
As far as the issue of linguistics is concerned, whether or not the English transliteration should be rendered as "hippocamp" isn't very relevant, considering this is not how the word is generally transliterated. However, names in mythology often have important allegorical, metaphorical, or even literal meaning which is important to the understanding of that which they refer to; names in medicine have no such importance. Whether hippocampus or hippocamp, the name is significant, whereas the part of the brain known as the hippocampus could just as easily be called the figgle-foogle and mean exactly the same thing. The term is completely insignificant in that context. Obviously, this isn't about which term is "correct". They are both correct and should be presumed of equal import if we are not to support a particular POV. The only issue is which usage is more common, and outside the field of medicine/anatomy, the usage that takes up the bulk of this page is effectively non-existent. --Corvun 02:01, August 23, 2005 (UTC)
  • You're arguing that the mythological name is significant (more than the well-defined, immutably named anatomical definition), yet you also are claiming that the English transliteration isn't important and it doesn't matter if it's "hippocampus" or "hippocamp". You can't argue both sides simultaneously, and a wikipedia search can't redirect a user to the nebulous quality embodied by the Greek mythological character. You argue that a Google search only proves that the anatomical definition has more references. Well if there are far more references, then wouldn't that make it a more likely Wikipedia search as well? I've given at least one qualitative piece of evidence, and all you've countered with is a personal feeling regarding what you think people would probably be searching for. That's not evidence.
This is all a moot point right now anyway as there isn't even an article on the Greek mythological creature. There's a hippocampus_(mythology) page that redirects here, and there's the List_of_Greek_mythological_creatures that has the name in a list. This can't be more important creature in mythology than a currently heavily-studied, heavily-taught important piece of anatomy. If you can't argue against my attempt at quantification, and continue to counter with a belief that is not-provable, I don't really know what else to say. Semiconscious (talk · home) 03:07, 23 August 2005 (UTC)
You know very well I wasn't arguing "both sides" of anything, and your claim that I was is a distortion that completely ignores the issue raised by equivocating transliteration with etymological definition -- two very, very different things. I'm not here to provide "evidence" for anything. All I'm saying is that there definitely needs to be a separate page for Hippocampus (anatomy), and possibly needs to be a separate page for Hippocampus (mythology) even if it's a stub. If we can't agree on which usage is more common, it seems sensible to split the difference per my suggestion. Keeping a page on Hippocampus filled with information on a single, obscure use of the term used nowhere outside of medicine and anatomy should not be an option. And if you feel the same is true for the Hippocampus from mythology, then obviously this page needs to be a disambiguation rather than being used for one or the other. --Corvun 04:12, August 23, 2005 (UTC)
Clearly I don't know very well you weren't arguing both sides of anything. If it had been clear, I wouldn't have said it. What purpose do I have to lie here? If you're not here to provide evidence for anything, then we aren't getting anywhere, are we? You seem to be arguing two sides of a similar point. You aren't giving any information beyond "I think my way is better" which is not a way to make a convincing point. I'm not saying I don't think there shouldn't be a hippocampus (mythology) article — of course there should be — I just think it's such a minor definition compared to a topic that is overwhelmingly researched by people of all walks of life and scholarly interest.
From what I've shown, the two topics seem to be far from "equal import" as you say. I think the top of the current, anatomical hippocampus page should have a link to "hippocampus (disambiguation)" under the main header. But then again, I don't really care about this; I just think you're incorrect in your statement and acting rather illogically by not offering any proof and arguing based upon your feelings. If you want to track down all the pages that reference the anatomical hippocampus and relink them to hippocampus (anatomical), and write a hippocampus (mythology) page, and then make the hippocampus page a disambiguation page, then we should wait to get others' input, perhaps taking this to arbitration. Numbers are important here, and I've tried to offer some. We're not going to get anywhere, so I'm curious to hear what the Wikipedia powers-that-be think of this. What do you say Mr. Corvun? Semiconscious (talk · home) 17:41, 23 August 2005 (UTC)
Semiconscious, you went ahead and made the argument I decided against making when I first saw Corvun's claims. After some thought, I decided against it, as it's hard to say which usage of the word is more common, since the groups who use the different meanings don't seem to overlap much. Personally I know a fair amount of greek mythology and I don't recall ever hearing about the Hippocampus, but that doesn't mean anything. Corvun's argument that the name of the brain region is unimportant but that the mythological beast's name really matters is quite silly, but his point about the creature having only a single line at the bottom of this long article still stands. Because this article also mentions a third and fourth usage of the term, for the seahorses and a Harry Potter character, apparently, I think a disambiguation page is called for as the best solution. Furthermore, because, after years of wikipedia being up, the anatomical term has developed into a full article while the mythological term remains three sentences, I think it's fair to let the anatomical term keep the main Hippocampus entry. I think that reflects a general agreement that the anatomical term is the primary meaning in use these days. Digfarenough 13:18, 25 August 2005 (UTC)
Herein lies the POV problem. Semiconscious, the point I was making, which in your over-eagerness to "debate" you completely missed, is that neither use of the term is "more correct". Digfarenough, of course my argument that the name of the brain region is unimportant is silly, and so by intent. The both of you seem to be immersed in a sea of peripheral issues and are unable to stand back and look at things with a NPOV. It is not our place to decide which usage is more important. Deciding that the anatomical term is the "primary meaning" and that "it's fair to let the anatomical term keep the main Hippocampus entry" is POV. This is the big POV problem. This is why I didn't just make a separate disambiguation page to begin with, because the disambiguation page belongs in this namespace. --Corvun 03:50, August 26, 2005 (UTC)
The more common usage for hippocampus is the anatomy definition by far. Even the dictionaries agree (both the dictionary dictionary.com and the Oxford dictionary), never mind the numbers on Google which Semiconscious has already quoted. If anything, this page should stay and any other pages such as hippocampus (mythology) should be linked off this page or hippocampus (disambiguation). I expect that the vast majority of people doing a search for the word "hippocampus" would be looking for the brain structure. It's like the article for Sydney - it obviously should be about the city of Sydney in Australia, therefore there is a small line at the top for Sydney (disambiguation) - instead of having the main page of Sydney be a disambiguation page itself for Sydney, Australia and other meanings of Sydney. That's the way to do it. Alex.tan 19:41, August 26, 2005 (UTC)
  • Alex.tan: thanks for the info. This is the exact point I was trying to make. Corvun, I understand the point you have been repeatedly making, despite your somewhat rude indication otherwise (e.g., "in your over-eagerness to 'debate' you completely missed"). In my last comment I suggested exactly the solution Alex.tan is proposing now. I'm not sure why I'm getting this slightly hostile reaction from you. This is not an instance of non-NPOV, no matter how many times you say it is. There are many other pages that do exactly what Alex.tan and I suggest, hence the existence of disambiguation pages on wikipedia.
  • Anyway, I've now created a hippocampus (disambiguation) page since you wouldn't comment on this idea and chose instead to just kept reiterating the same point. If you still disagree or just keep making the same argument, I will request arbitration and we can take this to a vote, because we're just going back and forth at this point and you don't seem to be taking any steps to fix the situation or address any of the stronger counter-arguments. I really am sorry that I seem to be upsetting or annoying you; I've tried to be calm, rational, and address your arguments and apologize if I'm giving you the impression that I'm not understanding you. Semiconscious (talk · home) 21:49, 26 August 2005 (UTC)
And yet again, Wikipedia's NPOV policy has been flushed down the toilet. And people still wonder why Wikipedia is the laughing stock of the internet. --Corvun 22:34, August 26, 2005 (UTC)
  • You are a very confusing person. What's going on here; why are you being so hostile and negative? I am really working to resolve this with you, so please help me out. Where in the NPOV policy page does it state that every topic with multiple meanings must point to a disambiguation page, despite wide disparity in usage between the two terms? I've read and reread the thing, and I can't find anything to that extent. If you show me where in the policy it states I am wrong, I will back down and stand by your side.
  • And where does "the laughing stock of the internet" thing come from? Semiconscious (talk · home) 23:09, 26 August 2005 (UTC)

Consensus seems to be that this page should be about the anatomical entity, and that remaining meanings, including Corvun's mythological creature, should be disambiguated from it. There is no violation of NPOV here - the only problem is priorisation. This kind of problem is typically solved by community consensus. I've seen these debates on several other pages, and it is always a matter of emphasis. I thoroughly disagree with the "laughing stock of the internet" appellation. Apart from being wrong (Wikipedia is heavily cited, even by the reliable news agencies) it also reflects a massive misunderstanding of the power of Wiki in general. I think a retraction would be appropriate. JFW | T@lk 21:52, 27 August 2005 (UTC)

Im probably a bit late for this - but you say the hippocampus region is only important if you are persuing medicine? You said yourself you learned about it in psychology, and knowledge of it is extremely important in many other fields. If you are going to say that, then who aside from a greek mythologist would need to know what hippocampus creature was? I think learning and memory is a more important part of the world today than greek mythology is. This region of the brain is responsible for you knowing what the hippocampus mythological creature is.thuglasT|C 23:22, 25 February 2007 (UTC)

[edit] Location/Image

I think it would be good if someone could add to the caption of the first picture: is this a view from below or above, and where is the front? AxelBoldt 06:48, 18 May 2006 (UTC)

Done. --David Iberri (talk) 19:03, 18 May 2006 (UTC)

[edit] Merge from cornu ammonis

Cornu ammonis is another name for the hippocampus and is used to identify its different regions. Besides the few other bits of info on that article, is there much more to say? If not, I propose that info be merged here. --David Iberri (talk) 02:21, 24 May 2006 (UTC)

Hm... I can't think of any reason not to merge it here and redirect. I don't recall the last paper I read that made a major distinction between cornu ammonis and hippocampus (except, I suppose, for some anatomy papers where the authors want to be very clear). Given that the dentate gyrus only sends outputs to the hilus/CA4 and CA3 and that, from a gross anatomical perspective, they are basically one unit, I support merging. Digfarenough 23:11, 12 July 2006 (UTC)
Actually, I have a better idea. I was just writing up some more detail about the hippocampal subregions and it occurred to me that it may end up having more detail than the actual hippocampus article should have. Perhaps, instead, we should include only a simple description of the connectivity and such of the subregions on this page, then put more detail about CA1-3 or 4 on the cornu ammonis page, expand the dentate gyrus page, and then link to those two from this page. Probably should expand the subiculum too and include that. I don't know the subiculum terribly well though, and I don't know a lot about interneurons in any of these areas, so I may need assistance with some of the detail. I'll finish writing up the CA1-4 info tonight and put it up tomorrow. I think that given how well studied the hippocampus is, there should be plenty of information to spread across the pages. However, if you think we should put it all here at first until it gets too long, I'd also support that (but when it does get too long, I think the cornu ammonis page is a good place to put some of the information). Digfarenough 00:13, 13 July 2006 (UTC)
I like your idea of giving an overview here and then linking elsewhere for details. But I'm wondering whether the subfields should be discussed at Cornu ammonis or whether CA should just redirect to Hippocampus. I'm leaning towards the latter because of the synonym issue. We could put the detailed CA anatomy at, say, Hippocampal subfields. What do you think? --David Iberri (talk) 14:20, 14 July 2006 (UTC) P.S. Great additions over at Cornu ammonis.
I think the Hippocampal subfields article is a good idea. Since I already discussed the hilus/CA4 on the CA page, which is more often considered part of the dentate gyrus, it makes sense to go ahead and add a list of the strata in DG and a new subfield entry for the fascia dentata. So Cornu ammonis should probably be moved to Hippocampal subfields. Here's a question though: should the subiculum be discussed on Hippocampal subfields? I'm not as familiar with it so I don't have much to say about it. In my mind, the terms go as follows. The dentate gyrus contains the fascia dentata and the hilus. The hippocampus proper contains fields CA1 through CA3. The subiculum is just the subiculum (the presubiculum and parasubiculum are poorly named, as they are quite different than the subiculum). The hippocampal formation then contains the dentate gyrus, the hippocampus proper, and the subiculum. Cornu ammonis contains CA1 through CA4 if one goes by Lorente de No's convention. So in a sense there's no neat and clean way to separate these things out, as there's a fair bit of overlap in many naming conventions. I guess the easiest thing to do is, on the hippocampus page, give a brief breakdown of the hippocampus into DG, CA1-3, and Subiculum (letting CA4 be part of DG), and have that link to a main article called Hippocampal subfields. Whew.. that was a lot... Digfarenough 18:24, 14 July 2006 (UTC)
That's my understanding of the anatomy too. Regardless of the overlap, which is probably unavoidable, I support the organization of articles you suggested. Also, to answer your question, I'd give the subiculum its own article and reserve Hippocampal subfields for CA1-4. Cheers, David Iberri (talk) 20:00, 14 July 2006 (UTC)
I've gone ahead and done the move to Hippocampal subfields, with a brief note there about Subiculum that links to its main article. I am just about to make a few more changes to reflect the new title and will make some slight changes on this article to reflect the move. If you care to help out in an easy way, would you mind helping me go through the pages that linked to Cornu ammonis [1] and making them redirect to hippocampus? I'm not sure how much time I have right now, so if you could take a look when you get a chance, I'd be much obliged. Otherwise I'll get to it at some point this weekend. Digfarenough 20:24, 14 July 2006 (UTC)
I'm a bit busy at the moment, but will chip in when I get a chance. Cheers, David Iberri (talk) 06:29, 16 July 2006 (UTC)
(dropping back on the indentation). 'Tis no problem, I just redirected cornu ammonis to the hippocampus article and that took care of all the links. My guess is that it's safe to just leave it like that. Digfarenough 17:41, 16 July 2006 (UTC)

[edit] Reproductive cycle?

On June 8 2006, an IP user added the claim "The hippocampus also plays a vital role in the reproductive cycle." I am not familiar with this claim. Does anyone have a reference for it? This IP address was apparently warned twice for vandalism a few days later (and vandalized the amygdala article the same day as this addition), which I take as further evidence to question this addition. I will remove it pending a reference. Digfarenough 20:57, 13 July 2006 (UTC)

I've never heard this claim before. A PubMed search for hippocampus reproductive cycle gives only a handful of results. --David Iberri (talk) 14:37, 14 July 2006 (UTC)

It is not directly related, this comment should be removed. People with damaged hippocampus regions function very normally, they just forget stuff cant form new explicit memories. thuglasT|C 23:24, 25 February 2007 (UTC)

[edit] Hilar mossy cell

Mossy cells of the hilus are mentioned in the article. It would be great to have a separate article about them, if they deserve it. I've read that the loss of this type of cells is somehow implicated in temporal lobe epilepsy. --CopperKettle 12:08, 9 September 2006 (UTC)

[edit] Hormonal issues?

I recall distinctly from research a couple of decades ago that hippocampectomised Sprague-Dawley rats exhibited elevated [3x normal] levels of ACTH, thus implicating the hippocampus in a basic feedback mechanism. I've seen nothing since then following this issue, nor do I see anything on these pages discussing [what may be]the more basic functionality of the hippocampus, particularly in its relation to hypothalamic function. It may also be that having abandoned that vocational path after my degree, I've missed further work in that area. Obviously, the expected behavioural effects of this expected elevated ACTH level does not seem to be present in humans, were the results consistent with those reports. Comment, please? —The preceding unsigned comment was added by Nyuszika45 (talk • contribs).

I can only comment, can't really answer your questions as ACTH-related matters (and molecular things in general) are outside my area of expertise. The hippocampus these days is generally accepted to be primarily involved in episodic memory (especially in humans, but in animals too). The dorsal half or so of the hippocampus receives a lot of spatial and sensory input, so it is thought to primarily represent spatial memory (but more and more the spatial memory is shown to be modulated by cognitive demands of tasks). Ventrally, the hippocampus is more closely associated with parts of the amygdala and seems to be related to fear conditioning, among other things. That, I think, is where the link to ACTH would come in, as fear is clearly related to stress, and stress in general has been shown to have effects on the hippocampus (e.g. reducing levels of neurogenesis in the dentate gyrus). In the past couple decades it seems that the focus has gone from the hippocampus just being yet another structure in the limbic system (i.e. Papez circuit sort of things) to being a significant structure in memory (episodic and, to a lesser extent, emotional). To summarize: although there are still researchers examining the sort of thing you mention, it seems to me that the bulk of the field has been concentrating on more general memory aspects (but that may only be because that's the research I do) so there is less emphasis on stress in general. Certainly if you know of relevant research, it would be worth adding to the article. digfarenough (talk) 16:24, 30 September 2006 (UTC)

In 1972, E. Endroczi’s work, “Limbic System, Learning and Pituitary Adrenal Function” was published by Akademai Kiado in Budapest. This work cited not just Endroczi’s work but other contributions prior to this date in establishing evidence pertinent to his research and that supportive work predating the book. Endroczi’s work showed quite different, often perseverative behaviour of rats with extensive hippocampal lesions. Concurrently, the work reviewed showed marked effects of ACTH infusion in facilitating shuttle-box learning. However, the most interesting aspect was the demonstration that hippocampectomised rats demonstrated a significantly higher level of plasma corticosterone than control rats, as well as the elimination of the normal diurnal fluctuations. When tested for exploratory activity, the hippocampectomised rats showed considerably more activity than controls, but this active state was characterised as more perseverative than exploratory. The hippocampectomised rats showed a significant deficit in passive avoidance learning. It is interesting that normal [non-treated or sham-operated] rats given various doses of corticosterone and hydrocortisone 30 to 120 minutes prior to passive avoidance learning sessions performed significantly better than hippocampectomised rats.

While much of this early work indicates a clear impact of hippocampal ablation on learning in simple tasks and routine behaviour, the increased routine [but not directive] activity seems indicative of a state where information is not processed and while the corticosterone levels may infer heightened activity levels, the actual behaviour is less focused than that of normal controls.

At the time, I hazarded an hypothesis that emphasised the consideration of heightened activity and commensurately decreased perceptual acuity as being implicated in the learning deficits displayed by hippocampal rats. However, the NIH did not seem to agree at the time. I have not followed up on this hypothesis or the others that might come to mind considering a potential learning-hormonal relationship. Knowing that there are effects of hormonal states that confound learning abilities, it might be postulated that hippocampal ablations generate confounding conditions. However, I’m sure that this issue has been thoroughly examined in the years since I did this work. So, while I am not aware of the answers, that does not mean that this question has not been considered. It is also obvious from the extensive work done with human subjects having accidental hippocampal damage that serious short-term memory function virtually disappears with hippocampal damage. However, I have not seen anything on hormonal states of hippocampal damage patients.Nyuszika45 01:58, 23 November 2006 (UTC)Douglas Schulek-Miller

[edit] Move Anatomy further down?

Excellent article. I would only suggest that you move the (excellent) Anatomy section further down. While it's interesting to me, and while I would refer to it myself if I were reading a journal article and wanted more details, it's fairly technical, and you'd have to be pretty familiar with brain circuitry to get through it or understand why it was important. OTOH, the sections on role in memory and history are immediately understandable to a non-specialist reader. Nbauman 01:44, 21 January 2007 (UTC)

That seems quite reasonable. I'll go ahead and do that. Thanks for the suggestion! digfarenough (talk) 18:31, 21 January 2007 (UTC)

[edit] Memory

The start of this article explains what types of memory a lesion to the hippocampus will affect (declaritive, episodic, etc.) and what it will not affect (procedural, etc.). A much simpler catagorization would be -Lesions prevent formation of explicit memory and -Lesions do not prevent formation of implicit memory these two catagories were founded on lesional studies of the hippocampal area (and anterograde memory loss of a disorder caused by long-term alchoholism (which i forget the name of) primarily and should surely be included in the article. I thought about doing it myself, but i wanted to run this by other editors and i also find the wording difficult to edit. thuglasT|C 04:51, 27 February 2007 (UTC)

Sadly, those two articles are in a sorry state. I still think explicit and implicit should be included as the main catagorization however. thuglasT|C 04:56, 27 February 2007 (UTC)

To be technical, there are some forms of implicit memory that hippocampal lesions impair, trace conditioning, for instance (though I think Larry Squire argues that that only occurs when the subjects are aware of the contingency). There's also evidence of other roles of the hippocampus in implicit memory [2], and evidence for implicit learning of contexts [3]. As far as I know, the jury is still out on that claim, though you could look at Larry Squire's work, as he does a lot on the link between the hippocampus and explicit/implicit memory. digfarenough (talk) 18:19, 27 February 2007 (UTC)

I have read a lot on the hippocamous and e/i memory. If by trace conditioning you mean mirror tracing tasks - all patients i have heard of with destroyed hippocampi are able to do this. I also know people are able to recoginise songs and be conditioned through puffs of air to the eye and many other classical conditioning teststhuglasT|C 01:39, 28 February 2007 (UTC)

By trace conditioning, I meant something like this: [4]. Probably one of the better reasons for using episodic memory instead of explicit memory is that explicit memory refers to both semantic and episodic memory (and also: what is explicit memory in animals? I suppose it depends on your definition... granted, Tulving seems to still believe that only humans have episodic memory, though the recent paper from Clayton's lab might be the final nail in that coffin). I recall there being some evidence that HM has slowly formed new declarative memories, suggesting either a lack of a hippocampus greatly slows down creation of new declarative memories or that he still has a small amount of function hippocampus remaining. That's sort of an aside, though. But I think the fact that the hippocampus is needed for contextual fear conditioning shows that its role isn't purely in explicit memory (though, again, I could be wrong: maybe contextual conditioning would only occur in humans if they are aware of the contextual contingency). digfarenough (talk) 20:58, 28 February 2007 (UTC)

Are you certain that HM had absolutely no hippocampus? I somewhat recall there being a very small proportion left - perhaps this would explain HM forming new declarative memories. Also, ive breifly read ethology articles maintaining animals do have episodic memory. I personally believe that people dont believe it exists because its hard to prove. Reminds me of strict behaviourism. thuglasT|C

Yeah, I'm sure animals do (well, fairly sure). If they don't, the paper I'm about to submit might be met with skepticism... There was also a paper by, I think, Fortin, Agster, and Eichebaum in 2004 or so doing ROC analysis on rats that showed differential contributions of recollection and familiarity, suggesting at least an episodic-like process. But the Clayton paper is what provides really good evidence, I think. That might be true about HM, I forget, and I'd have to upstairs to ask someone who'd know, which I'm too lazy to do at the moment. :) digfarenough (talk) 21:22, 28 February 2007 (UTC)

[edit] Location - misleading

The hippocampus is not part of the the temporal lobe; to my knowledge, it is located structually within(under-ish) but still seperate in classification from the temporal lobe which is a part of the cortex which the hippocampus is NOT (it is part of the limbic system). Best way i can explain this is that the hippocampus is jelly in a doughnuts crust but it is not part of the crust.thuglasT|C 05:04, 27 February 2007 (UTC)

I dunno, I think it's fair to say it's part of the temporal lobe. In both rats and humans, it's right next to entorhinal cortex and subiculum (see the last figure in the article, for instance). But the hippocampus is indeed cortex, it just isn't neocortex. digfarenough (talk) 18:10, 27 February 2007 (UTC)

I was wrong - it is part of the cortex, but it is NOT part of the temporal lobe. It is under it. the temporal lobe is a lobe, the hippocampus is part of the limbic system which is not a lobe. The hippocampus evolved far before the temporal cortex was there as the temporal lobe deals with extremely complex functions (face perception in the infrotemporal cortex) and the limbic system (while equally amazing) deals with less evolved functions such as learning that we are less aware of such as learning emotion and motivation. thuglasT|C 01:36, 28 February 2007 (UTC)

(Computer crashed in mid-reply!) Basically I was saying: limbic system is not really a thing, it's a grouping someone came up with. Notice that orbitofrontal cortex is considered part of the limbic system, which is clearly neocortex and part of the frontal lobes. Also, the temporal lobe contains primary auditory cortex and, e.g., birds have both an analog of primary auditory cortex as well as one of hippocampus, so the two may have grown up together, in a sense. Certainly the Clayton paper I've mentioned shows that birds seem to have episodic memory. If you do change the wording, you shouldn't say "under" but rather something like "medial to". In humans the hippocampus is indeed ventral and medial to other temporal cortices, but in rats it's just medial, not really ventral (since in rats the hippocampus is rotated a bit and flipped upside down, as I recall, compared to humans). digfarenough (talk) 21:26, 28 February 2007 (UTC)

You said the limbic system isnt really a thing... to me if many papers/textbooks maintain is a grouping i would think it is a 'thing' is as if the system was not very closely related in function, structure, or evolutionary time line it probably would not be grouped together.

I was thinking under anyway, but i was trying to think of a better word. Maybe what we could compromis at is located structurally inside (or below/under) the temporal lob. I just don't like the idea of people thinking it 'located inside' means it is a region in the temporal lobe. This sounds good to me - what about you I apologize if it sounds like i am arguing - i just like to think about brains. :) thuglasT|C 21:48, 28 February 2007 (UTC)

You might be interested in this paper by Murray and Wise [5], arguing whether it is useful at all to talk about the "medial temporal lobe." I mention it because that paper along with Swanson and Petrovich (1998) argue that the amygdala isn't even a single thing, but rather just a term for a collection of anatomically nearby structures. That's just to say that traditional groupings of things sometimes have to change in light of newer data. Personally I still hear lots of people refer to the hippocampus as being part of the medial temporal lobe, so I have no problem with claims like that. Even the Murray and Wise paper isn't saying that the HC isn't part of the medial temporal lobe, they're just arguing that the MTL isn't a system with a single function, but rather a collection of functionally distinct components, which I also agree with. digfarenough (talk) 22:06, 28 February 2007 (UTC)

ill read that as soon as i get home - is adding structurally good for you? its good for me. this to me suggests it is not the same as the temporal lobe... thuglasT|C 23:04, 28 February 2007 (UTC)

Yeah, that sounds fine with me. digfarenough (talk) 23:45, 28 February 2007 (UTC)
Hm, the new wording sounds odd to me. "Structurally inside" is awkward and to me doesn't carry any different meaning than "in". I don't see any problem with considering the HC as part of the temporal lobe, as I've never heard the temporal lobe described as an exclusively neocortical structure. --David Iberri (talk) 00:38, 1 March 2007 (UTC)
I agree its a bit awkward i couldnt find a better wording. I guess the way i want to say it is the heart is located structurally 'in' the skin, but not categorically. Whatever - if more than one person doesnt agree - revert it. thuglasT|C 16:35, 1 March 2007 (UTC)

I tried to make it better. Dig im going to leave this one up to your approval. thuglasT|C 23:00, 1 March 2007 (UTC)

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