Re: Memory is not infinite
- From: "*Hemidactylus*" <ecphoric@xxxxxxxxxxx>
- Date: 21 Apr 2006 21:05:31 -0700
r norman wrote:
On Wed, 29 Mar 2006 08:22:35 -0700, dkomo <dkomo871@xxxxxxxxxxx>The ecphory is indeed as important as the engram itself. It's in the
wrote:
Cyde Weys wrote:
I've always learned that memory is infinite, both in the number of things
you can remember and in how long you remember it .. the catch, they say, is
that the associations get overwritten and although it may all be stored
somewhere in there, there's no practical way to retrieve it. I learned
this in Psychology in high school and also in Human-Computer Interactions
in college. But it always rang false to me.
Turns out I was right! From Science News 2006-03-18, Vol. 169 pg. 165,
"Grown-up Connections" -- Researchers did experiments on mice and monkeys
where they used a special infrared imaging technique (combined with a
genetically-modified cell labeling substance) to image the connections of
axons and dendrites in synapses in the brain. They discovered a remarkably
high turnover rate in the synapses: up to double digit percentages per
month! So, over the course of a year, more than half of the synapses
resent originally would be gone and replaced with new connections!
So yeah, it appears the brain can't remember infinite things because it
needs to scavenge old connections for new memories, and also, memory length
is hardly infinite. You might almost say it has a half-life! Like, I
remember very few things from when I was in elementary school - and the
things I remember are all very important moments that I've thought about a
lot since then, reinforcing them. The rest of the day-to-day memories ...
utterly gone. Whereas I can still remember a lot of trivialities of day-
to-day life from a year ago.
So how does this explain the fact that during brain surgery when parts
of an awake patient's brain are stimulated by electrodes, they recall
with full and vivid sensory detail memories from their earliest lives
that they hadn't accessed before the surgery? Or is this just an urban
myth? Penfield, I believe, was the first neurosurgeon to report on this
phenomenon.
Also, I have memories from childhood popping up all the time, seemingly
for no apparent reason, as do a lot of people. They may be a bit hazy,
but they are definitely real. I think the conclusions you drew above
are oversimplied to say the least.
Cyde's musings are rather a bit oversimplified, to say the least.
Cyde argues two points: first that memory is not infinite in extent or
in duration, second that the problem with aging is that the actual
memory storage is erased, not merely the retrieval ability. The
evidence is that brains recycle and regenerate synapses.
It is quite true, as many have pointed out, that everything except
mathematical concepts must be finite in extent although they may be so
large as to be essentially "unlimited in practice". Similarly
everything must be finite in duration since we can predict an end to
the universe.
But the second point is more difficult. The recycling of synapses may
in fact retain their function; just as the material in bone is
recycled without changing the structure or function of our skeletal
systems. Because there is active turnover of specific synapses does
not prove that memory is necessarily lost. Also, if this synaptic
revision is altering function, it could well be that it is the recall
mechanism that is being recycled to make available new connections and
the memory, itself, is still intact.
cueing. Ask the right question and you might trigger a golden oldie.
There's the difference though between recognition and recall. You might
not be able to bring a decently detailed memory of a past event to the
foreground even with great effort, but you might recognize something
about it as its on the tip of your tongue. That's why multiple choice
are often easier than essay.
One problem with cueing is the miscue. If asked in a leading way one
might remember things that didn't happen. Plus two or more fuzzy
fragments from long ago might fuse to form a distorted composite, much
like this post I'm typing :-) That serves as a creative spark as you
juxtapose things that are seemingly disparate into a "new" way of
thinking. Aha!
So-called flashbulbs. Remember what I was doing during the Challenger
That would agree with the
traditional dogma that Cyde originally learned. Finally, it may well
be that some, even many, memories are lost in this kind of reformation
but that there are others that, for one reason or another, are
preserved indefinitely
and Columbia disasters fairly well.
Touche. Ain't nothing necessarily inferior about psychology, though I
and that, in the human brain there are enough
of these permanent memories to be considered "unlimited". Finally, it
would be a bit more impressive if Cyde's recollections were based on
neurobiology courses, not on high school level Psychology or college
level computer engineering courses.
suppose high-school level gen psych and college level neuropsych are
two different creatures altogether. Neurobiology is cool but it's a bit
removed from the everyday where social psych is more appropriate. Not
mutually exclusive, but the average person might find more "emergent"
psych material more useful in understanding themselves than learning
the nitty gritty of synaptic connections, though some neurochemistry
can't hurt when it comes to knowing how neurotransmitters ,
neuromodulators etc influence behavior.
.
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