From: Alex Ramonsky (alex@ramonsky.com)
Date: Sat May 31 2003 - 06:12:36 MDT
Brett Paatsch wrote:
>[snip] Neurons (nerve cells) with
>dendrites, axons etc are "constantly" changing shape connecting and
>reconnecting with each other
>
This is synaptogenesis. We don't make many new neurons after childhood
but we can increase or decrease the number of connections between
neurons and the number of receptors for neuro and other chemicals.
> in relation to intracellular signalling (which
>would turn genes on and off).
>
Specific genes are activated to achieve LTP (long term potentiation).
LTP is involved in several kinds of memory formation.
> Genes don't *directly* make anything
>structural in a cell, structural like a dendrite, rather the structure of
>the
>cell is altered as a result of interactions from proteins (cytokines,
>hormones etc) they cause other particular proteins (the physically
>structural components of cells) to be expressed, transported to the
>relevant site in the cell and assembled into the structure or made into
>an enzyme (a working protein). The whole thing is dynamic not static.
>
Spot on.
>
>Already memor*ized* information is unlikely to require the same sort
>of physical construction of connections - they're already there.
>
Every time you recall a memory, you have to produce certain proteins in
order to keep it in long term storage afterwards. If I inject you with a
glutamate blocker right after you finish reading this, you won't be able
to remember this email. If you go out somewhere new, you'll have
difficulty navigating the same route tomorrow because you won't remember it.
> Maybe
>though, there is some level of maintenance activity required for us to
>retain the connections (memories) that are in place as the protein
>physical constructs would certainly degrade over time.
>
Only if the synapses decrease in number. This can only happen if they're
not used, (you might say, 'charged' regularly, or if they're interfered
with by, for example, glutamate blockers. The lifespan of a long term
memory is dependent on its synaptic connections. The number of these we
make depends on the weighting of the sensory input by emotion and
imagination.) But any memory is updated and changed according to your
current beliefs, ideas and motivations every time you recall and resave
it (You cannot recall without a resave).
> Perhaps accessing
>a memory is stimulation enough to cause some sort of minor maintenance
>or reinforcement construction to be done with expressed proteins.
>
Yes it is. Both a pre- and a post-synaptic cell must be firing to be
'important' enough to make a long term memory. There's lots more, but
I'll leave it at that for risk of getting boring.
Ramonsky
>
>But, hey, I'm getting out of *my* depth here pretty quick and stand
>ready to be corrected.
>
>-Brett Paatsch
>
There's lots more, but I'll leave it at that for risk of getting boring.
Ramonsky
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