Questions on memory storage...

Ruadhan O'Flanagan rof at
Sun Aug 11 07:04:03 EST 1996

csorg at (Chris sorg) writes:

>	I'm curious as to how the brain stores memory. As to specifics, I know
>this is a pretty broad question with more theories than answers, but I have 
>a few specific questions in mind:

>	(1) Is the brain the ONLY place where memories are stored, or
>	can nerves throughout the body have memory? 

It sort of depends on what type of memories you mean. Memories can exist
in nerves throughout the body in the form of habituation and sensitization,
which can serve, for example, to dull reflexes such as the gill-withdrawal
reflex of the marine snail Aplysia Californica(habituation). Alternatively,
sensitization(which could occur after a particularly noxious stimulus to
the tail of Aplysia), can cause the same reflex to be heightened. The
mechanisms for these have been studied in detail.

However, if the sort of memory you refer to is our more familiar type of
memory(memories which we can recall and think about etc.), then these are
pretty much restricted to the brain. The reason is that in order for a person
to think about a particular memory, the frontal cortex must be able to send
signals to the area where that memory is stored, and those signals must
then propagate back to the frontal lobe. Motor efferents etc. have only
indirect methods of "reporting" back to base(e.g. through the activation
of proprioceptive sensory neurons).
>	(2) Can nerve ganglia act as "small brains" for activities such
>	music playing and gymnastics, ie complex muscle movements?

These are a bit more complicated than the other functions performed by the
various parts of the brain, because the temporal nature of the tasks makes
it impossible for single sets of simultaneous pulses to suffice. There are
more theories than explanations about this. 

My two cents can be seen at 

>	(3) Is the old, outdated idea of engrams back 'in' as a way of
>	viewing memory storage in the brain? Is memory grouped in sets
The elusiveness of the engram caused it to lose popularity a while ago. Some
theories of memory use variants of the idea, but the patterns must necessarily
be delocalised.

>	(4) Biological mechanisms for memory: are they neurochemical
>	changes, physiological changes (such as denser dendritic 
>	connections), both, or none of the above?

Most of the identified mechanisms of learning seem to involve physiological
changes, such as dendritic growth etc, but neurochemical changes are often
part of this process. Long term potentiation in the hippocampus is a good
example of this.

>	I guess until I wrote this I thought I had some minor understanding
>of memory, now I realise I probably know nothing. Any help or books or
>whatever would be of great assistance to me. TIA!

You are not alone. What is "known" about memories, particularly explicit
memory, amounts mostly to vague implications of various parts of the brain.

Ruadhan O'Flanagan

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