fact check - cells multiplying in the brain?

[dtilque]

@njtt

The fact that neurogenesis occurs to some degree in parts of the brain “involved in memory and learning” (actually that would be pretty much all the brain), is not itself evidence that neurogenesis is involved in the process of memory and learning. It almost certainly isn’t in any relevant way.

I disagree. From what I’ve read, neurogenesis seems to be an important part of creating long term memories.

As to your last claim, i would like to see the cite, as what you are implying seems very unlikely to me. Laying down a memory can, and normally does, happen very rapidly. Neurogenesis, especially the growing of a new cell to the point of size and morphological complexity where it can do anything cognitively useful, is bound to be a much slower process. I find it pretty much unimaginable that neurogenesis plays any role in the formation of particular memories, although it may play a role in preparing the brain for further learning of a particular sort, or something like that.

Unfortunately, I can’t find the cite. It was something I read in Science News maybe a year ago. SN has recently done a major remodeling of their website and searches on it don’t seem to find anything from before this year.

However, I did find this paper (pdf) from a few years ago summarizing what was known then.

Thousands of new neurons are added into the adult hippocam-
pus each day. However, most of the new cells do not survive. In
fact, over half of them, if not more, die within just a few weeks of
their birth. One of the most effective ways to keep these cells from
dying is by learning.

OK, this paper is about learning rather than just any novel experience, as the other paper reported. However, learning falls under the category of novel experience so there’s not really a conflict here. The earlier paper stressed learning because that’s what they had the rats in their experiments do.

Anyway, it’s my strong impression that new cells get incorporated into the brain as part of making long term memories. The brain constantly makes new cells in the hippocampus, but only those within a certain age (about 1 week old) get incorporated in these memories.

[njtt]

@dtilque

I disagree. From what I’ve read, neurogenesis seems to be an important part of creating long term memories.

I think you cannot have understood what you have read very well.

@dtilque

However, I did find this paper (pdf) from a few years ago summarizing what was known then.

OK, this paper is about learning rather than just any novel experience, as the other paper reported. However, learning falls under the category of novel experience so there’s not really a conflict here. The earlier paper stressed learning because that’s what they had the rats in their experiments do.

Anyway, it’s my strong impression that new cells get incorporated into the brain as part of making long term memories. The brain constantly makes new cells in the hippocampus, but only those within a certain age (about 1 week old) get incorporated in these memories.

Did you even notice the title of that paper? It is called “Use it or lose it: How neurogenesis keeps the brain fit for learning” [emphasis added]. It is not saying that neurogenisis is part of the learning process itself (which would be absurd, for the reasons I gave previously), it is saying that neurogenesis (in certain brain regions) prepares the brain for subsequent learning. It provides new cells, that in themselves embody no particular information, but whose connectivity may then be shaped into a meaningful form by subsequent learning processes (or, if not, the cell dies). This is essentially what I suggested in my earlier post:

@njtt

I find it pretty much unimaginable that neurogenesis plays any role in the formation of particular memories, although it may play a role in preparing the brain for further learning of a particular sort, or something like that.

I was speculating at the end there, but your cite suggests that my speculations (based on my general understanding of how the brain works) were broadly correct. It does not contradict me, as you seem to imagine, and it certainly does not confirm what you (and HazelNutCoffee’s friend) appear to be suggesting, and what I am denying, i.e., that neurogenesis is part of the learning process itself. If you still do not grasp the important distinction here, consider the difference between making paper and printing a book. It is the latter process that encodes information. The former (paper making) does not, and it is not part of the printing process itself, although, if you do not have a sufficient stock of paper already to hand, it is one of the necessary preliminaries that make printing possible.

[dtilque]

@njtt

I think you cannot have understood what you have read very well.

Perhaps. Or perhaps I read it with a more critical view than you did.

Did you even notice the title of that paper? It is called “Use it or lose it: How neurogenesis keeps the brain fit for learning” [emphasis added].

After reading the article, I came to the conclusion that that title is misleading.

It is not saying that neurogenisis is part of the learning process itself (which would be absurd, for the reasons I gave previously),

Well, you showed that what I posted in my first response was incorrect. I agree, it was. And it was most likely incorrect because I misremembered an article I read maybe a year ago.

OK, here’s what I got from the paper: New neurons are generated by the hippocampus every day, several thousand of them, although the amount varies depending on various environmental factors. When something new is learned, some of those new neurons that are about a week old are incorporated into the brain as new long term memories. Or rather the cells plus their connections and no doubt new or modified connections of older neurons are the new memories.

Now the hippocampus is a specialized part of the brain, so the new memories only have to do with its functions, which seem to be pattern matching and timing. Memories of other things are no doubt generated in other parts of the brain and may not involve new cells. Although for some things that rats don’t have (notably language) we have no idea if new cells are involved in those or not.

it is saying that neurogenesis (in certain brain regions) prepares the brain for subsequent learning. It provides new cells, that in themselves embody no particular information, but whose connectivity may then be shaped into a meaningful form by subsequent learning processes (or, if not, the cell dies). This is essentially what I suggested in my earlier post:

As far as I can tell, “shaped into meaningful form by subsequent learning processes” is a fancy way of saying these new cells are incorporated into memories.