# Memory Replacer: Remove old neurons containing useless information and replace them with new neurons **URL:** \ **Category:** Factual Questions\ **Created:** [February 9, 2013, 1:26pm UTC](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782 "2013-02-09T13:26:34Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![RaftPeople](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)\ **Post date:** [February 12, 2013, 2:31am UTC](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782/21 "2013-02-12T02:31:36Z")
> [@njtt](#): > > Yes, while it is in situ, but remove the neuron from its place in the brain and all that structure, the arrangement of axonic terminals and where they terminate, is gone. They are just blowing in the wind. The “information” their arrangement once embodies will not stay with the neuron when you remove it from its place, so in an important sense, the relevant sense, this information is not “in” the neuron. The value of the information is dependent on it’s location, but the information is there. > [@](#): > > Um, no. The DNA most certainly does not change. That is the whole point of DNA. > > Gene expression is _not_ a change in DNA. It is a (temporary, dynamic) change in RNA and protein, and (once again) there is no good reason to think that anything distinctive about the condition of a particular neuron’s RNA and protein will survive the cell being removed from its place in the brain. Again, it will not carry with or “in” it any information relevant to any memories it contributed toward encoding whilst it was in place. > > The DNA in the cell does carry data, of course, but not data relevant to any particular memory. Yes, it most certainly does. Here’s one of many many papers on the subject: [**Covalent Modification of DNA Regulates Memory Formation**](http://www.google.com/url?url=http://scholar.google.com/scholar_url%3Fhl%3Den%26q%3Dhttp://www.med.upenn.edu/ins/Journal%252520Club/Fall%2525202008/David%252520Sweatt/Miller%252520and%252520Sweatt%252520Reprint.pdf%26sa%3DX%26scisig%3DAAGBfm2AHfzhmLuK1KN9dKcJVKKF8dS3QA%26oi%3Dscholarr&rct=j&sa=X&ei=96cZUde9EKLFigLkyoDIDA&ved=0CC0QgAMoATAA&q=dna+methylation+memory+formation&usg=AFQjCNEYW14FcXStzlzr5YcbWXyYKCyVeg&cad=rja) Excerpt from abstract: “DNA methylation is a covalent chemical modifi-cation of DNA catalyzed by DNA methyltrans-ferases (DNMTs). DNA methylation is associ-ated with transcriptional silencing and has been studied extensively as a lifelong molecular information storage mechanism put in place during development. Here we report that DNMT gene expression is upregulated in the adult rat hippocampus following contextual fear condi-tioning and that DNMT inhibition blocks memory formation. In addition, fear conditioning is asso-ciated with rapid methylation and transcrip-tional silencing of the memory suppressor genePP1and demethylation and transcrip-tional activation of the synaptic plasticity gene reelin, indicating both methyltransferase and demethylase activity during consolidation.” ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [February 12, 2013, 12:05pm UTC](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782/22 "2013-02-12T12:05:10Z")
> [@RaftPeople](#): > > The value of the information is dependent on it’s location, but the information is there. > > Yes, it most certainly does. > > Here’s one of many many papers on the subject: > [**Covalent Modification of DNA Regulates Memory Formation**](http://www.google.com/url?url=http://scholar.google.com/scholar_url%3Fhl%3Den%26q%3Dhttp://www.med.upenn.edu/ins/Journal%252520Club/Fall%2525202008/David%252520Sweatt/Miller%252520and%252520Sweatt%252520Reprint.pdf%26sa%3DX%26scisig%3DAAGBfm2AHfzhmLuK1KN9dKcJVKKF8dS3QA%26oi%3Dscholarr&rct=j&sa=X&ei=96cZUde9EKLFigLkyoDIDA&ved=0CC0QgAMoATAA&q=dna+methylation+memory+formation&usg=AFQjCNEYW14FcXStzlzr5YcbWXyYKCyVeg&cad=rja) > Excerpt from abstract: > “DNA methylation is a covalent chemical modifi-cation of DNA catalyzed by DNA methyltrans-ferases (DNMTs). DNA methylation is associ-ated with transcriptional silencing and has > been studied extensively as a lifelong molecular > information storage mechanism put in place > during development. Here we report that DNMT > gene expression is upregulated in the adult rat > hippocampus following contextual fear condi-tioning and that DNMT inhibition blocks memory > formation. In addition, fear conditioning is asso-ciated with rapid methylation and transcrip-tional silencing of the memory suppressor > genePP1and demethylation and transcrip-tional activation of the synaptic plasticity gene > reelin, indicating both methyltransferase and > demethylase activity during consolidation.” Meh. Sure, we are all simplifying what is in fact a highly complex and dynamic situation here. The point is that your nitpick at what **Stranger** said was far more misleading, in the context, than the minor and appropriate oversimplifications in **Stranger** ’s post. Talk about the DNA changing, especially in the context of how neurons store memories, and even a well informed layperson is going to think you are talking about changes in base sequences, and actually storing memories in nucleic acids (which, once upon a time, was a serious theory of how the brain stored memories), not essentially temporary regulatory modifications like methylation. In any case, the pattern of methylation (and other possible “changes” in the DNA molecule, such as conformational ones) although it may well be relevant to specifying that the neuron should function as a neuron (as opposed to some other cell type) is most unlikely to be specifically related to the precise number and arrangement of synapses of the cell in situ, the thing that is actually believed to carry information embodying specific memories. The DNA, as methylated or otherwise, is not (and never was) telling the axon terminals exactly where to go. Indeed, if it did we would not be able to form memories. ---
**Author:** ![RaftPeople](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)\ **Post date:** [February 12, 2013, 4:40pm UTC](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782/23 "2013-02-12T16:40:14Z")
> [@njtt](#): > > Meh. > > Sure, we are all simplifying what is in fact a highly complex and dynamic situation here. The point is that your nitpick at what **Stranger** said was far more misleading, in the context, than the minor and appropriate oversimplifications in **Stranger** ’s post. I disagree. It’s misleading to claim the neuron contains no data. The neuron contains the current connections to other neurons (as do the other neurons) and the strength of those connections (as do the other neurons). These are the data (some of the data). > [@](#): > > Talk about the DNA changing, especially in the context of how neurons store memories, and even a well informed layperson is going to think you are talking about changes in base sequences, and actually storing memories in nucleic acids (which, once upon a time, was a serious theory of how the brain stored memories), not essentially temporary regulatory modifications like methylation. That’s why I put the “gene expression” in parens, to give a clue in a couple words what type of change was happening. > [@](#): > > In any case, the pattern of methylation (and other possible “changes” in the DNA molecule, such as conformational ones) although it may well be relevant to specifying that the neuron should function as a neuron (as opposed to some other cell type) is most unlikely to be specifically related to the precise number and arrangement of synapses of the cell in situ, the thing that is actually believed to carry information embodying specific memories. The DNA, as methylated or otherwise, is not (and never was) telling the axon terminals exactly where to go. Indeed, if it did we would not be able to form memories. You appear to be assuming something, I’ve never posted anything about telling axon terminals where to go. This was my original point with regard to changes to DNA and gene expression: “to maintain synaptic connections at the new level over the long term” Increased production of proteins are required to maintain the increased connection strength (based on what I’ve read). Even if more current info changes the exact mechanism, the bottom line is that changes to the neuron somewhere (in the nucleus, in the dendrites, wherever) maintains the new connections strength. And that connection strength is data. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [February 12, 2013, 7:12pm UTC](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782/24 "2013-02-12T19:12:52Z")
> [@DSeid](#): > > The other bit is that there is little doubt that memories are compressed and then recreated filling in the gaps with stuff that we make up as we remember but are sure is real. Or, more likely, what we say we remember is a combination of an abstracted notion of what we believe occurred and a confabulation built from other traces of other memories. We probably do not remember anything in a secure, relatively permanent, photographic way, but rather more like a history of an event as told by hundreds of people at the same time, despite the occasional impression that it is otherwise. ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [February 12, 2013, 7:53pm UTC](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782/25 "2013-02-12T19:53:37Z")
[quote=“Stranger\_On\_A\_Train, post:6, topic:649782”] Long term memory is not stored in individual neurons, but rather in the connections that are formed in between neurons… Thanks Stranger, for the information. Very enlightening! [Previous page](https://boards.straightdope.com/t/memory-replacer-remove-old-neurons-containing-useless-information-and-replace-them-with-new-neurons/649782.md?page=1)