Re: New Scientist on memory

Date: Sat 31 May 2003 - 20:19:39 GMT

  • Next message: Lawrence DeBivort: "RE: New Scientist on memory"

    > > From: "Lawrence DeBivort" <>
    > >
    > > Recalled from what?
    > From the past. Memory is the recall of events from the past. This is
    > the common sense view, and it's rapidly becoming the only viable
    > scientific view as well.
    > > From:
    > >
    > > > Though the author himself doesn't seem to realize it, the evidence
    > > > discussed in this article abolishes the notion that the brain
    > > > alone is responsible for memory. Every time we recall something,
    > > > the relevant memory trace in the brain is completely erased and
    > > > then "reconstituted" from scratch. If memory is nothing more than
    > > > stored information in the brain, there would be no way of
    > > > recreating the memory once it's been erased. The only explanation
    > > > is that we literally recall the past (often making mistakes in the
    > > > process) enabling us to reconstruct the memory after the neural
    > > > trace has been destroyed. Memory must be taken at face value-- as
    > > > a recollection of the past-- rather than simply the retrieval of
    > > > information from cerebral vaults. We may regard neural traces as
    > > > pointers to memories rather than the memories themselves.
    > > >
    > > > --TD
    > > >
    > > The article states that memory is not 'erased' so much as it is
    > > 'redynamized';
    > Let's take another look at the article:
    > > To study memory consolidation, researchers interfere with steps in
    > > the fixing process in order to test their influence on long-term
    > > recall. While doing this kind of work, researchers including Karim
    > > Nader of McGill University, Montreal, and Joseph LeDoux of New York
    > > University noticed something odd. They trained rats to associate an
    > > electric shock to their paws with a darkened box. The rats learn
    > > that the box is "nasty" and
    > freeze
    > > the next time they are put back. If, a few days after training, the
    > animals
    > > were given a drug to stop protein synthesis before being reminded of
    > > the conditioning stimulus - the sight of the training box - it made
    > > no difference to their ability to remember it. The memory seemed
    > > fixed and safely stored. But if the rats had a brief reminder of the
    > > stimulus just before the drug was given, then a memory that should
    > > have been fixed and stable seemed to be erased.
    > Every time you remember something, the relevant "memory trace" in your
    > brain is erased. Ordinarily, you simply re-establish the trace,
    > perhaps in modified form, in the act of recalling the event from the
    > past. But if something interferes with your ability to re-establish
    > the trace, such as a drug that stops protein-synthesis, you lose the
    > memory. The trace, which had already been erased, is now gone for
    > good. It's in the gap between recall, when the neural trace has been
    > liquidated, and the moment the trace is re-established, that the true
    > nature of memory is revealed. During that gap, your brain cannot help
    > you remember. It's up to you.
    > > But if the rats were reminded of the sight of the box just before
    > > the drug was injected, the result was precisely the opposite. Now
    > > the protein-blocking drug created amnesia.
    > When you recall something-- and the memory trace is instantly
    > destroyed-- you can still remember the event, but if you lack adequate
    > protein to re-establish the trace on the basis of your recollection of
    > the past, you'll never remember it again. The next time you try, the
    > neural trace will be gone, and you'll have no way of "tuning in" to
    > the memory.
    > > At both the synaptic level and the anatomical level, it was as if
    > > the consolidated memory had been released and needed to undergo the
    > > whole fixing process again if it were to be remembered.
    > If memory is contained in the brain, and the neural trace has been
    > "released," how can the memory be fixed again? On what basis is the
    > "fixing process" carried out? It can only be on the basis of our
    > recall of the past event itself.
    > Memory requires two things:
    > 1. a memory trace in your brain to point you to the memory
    > 2. your direct recollection of the past, on the basis of which you
    > re-establish the trace for later recall.
    > > The protein filaments that give
    > > the cells their internal shape have a half-life of just a few
    > > minutes. And the receptor proteins that stud the synapses need
    > > replacing every few
    > days.
    > > As Joe Tsien, a neurobiologist at Princeton University in New
    > > Jersey,
    > says,
    > > the brain you have this week is not the one you had last week. Even
    > > the
    > DNA
    > > needs to be repaired. So if "you" are essentially a pattern of
    > > synaptic connections, a tangled web of memories, then there is a big
    > > problem of how this pattern endures. "I don't know how people ever
    > > got this static
    > picture
    > > of the brain," says Tsien. "A memory trace would have to be a
    > > dynamic
    > thing
    > > just because of molecular turnover."
    > Memory is the basis of enduring self-identification. If memory were
    > nothing more than a pattern of synaptic connections, our sense of
    > enduring selfhood would indeed be illusory. But the pattern of
    > synaptic connections is not the memory itself, any more than "88.9 FM"
    > is identical to the songs you hear when you tune in to that frequency.
    > Enduring self-nature is not an illusion. We are not
    > auto-hallucinations.
    > > And the more you think about it, the more such dynamism makes sense.
    > > Susan Sara of the Pierre and Marie Curie University in Paris, who
    > > found indications of a reconsolidation effect in her own experiments
    > > in 1997,
    > says
    > > the real problem for the brain is not how well it can preserve the
    > > past
    > but
    > > how successful it is at integrating new learning with old learning.
    > Memories
    > > exist to make sense of the present - to recognise and understand the
    > world -
    > > and the brain needs to be able to optimise all its circuits,
    > > strengthening or generalising some connections while weakening or
    > > erasing others. Reconsolidation may seem a radical and unnecessary
    > > step for a brain that just wants to be a dormant warehouse. But,
    > > Sara says, if a memory becomes completely plastic every time it is
    > > roused, then it can be refiled in a carefully updated way. Active
    > > choices can be made about whether to merge the old and the new - or
    > > by contrast, to reinforce their separateness.
    > What kind of a storage system allows for stored information to become
    > "completely plastic" every time it's recalled? Wouldn't it make more
    > sense to simply modify it each time instead of erasing it and
    > "reconstituting" it from scratch? Sara is right about the importance
    > of memory remaining fluid so as to keep up with ever-changing
    > contexts. And this is why memory is not based on a storage system.
    > I think memory research is in a kind of twilight zone right now.
    > Researchers are unwilling to give up their old views despite the fact
    > that we now know memory is irreducible to the brain, and a neural
    > storage system doesn't even make any sense in the first place, given
    > the demands for flexibility. It just goes to show that a meme-- in
    > this case the culturally-ingrained habit of considering memory in
    > terms of neural information-storage-- is currently stronger than our
    > ability to examine this issue reasonably.
    > Ted
    The memory is not erased, it is simply 'fluidified', that is, 'unfixed' from its memory storage moorings. But it is still there during the active remembrance. It must be 'refixed' if it is to remain, and that usually happens by the very act of remembrance. However, this 'refixing' process can be interdicted by certain drugs. In this case, the 'unfixed' memory simply dissipates, thatis, it is forgotten, rather than being
    'refixed' in memory storage.
    > ===============================================================
    > This was distributed via the memetics list associated with the
    > Journal of Memetics - Evolutionary Models of Information Transmission
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    > see:

    =============================================================== This was distributed via the memetics list associated with the Journal of Memetics - Evolutionary Models of Information Transmission For information about the journal and the list (e.g. unsubscribing) see:

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