Working memory

F. Frank LeFever flefever at ix.netcom.com
Sun Mar 22 21:38:17 EST 1998



Perhaps it is my fault for putting that paranthetical clause in an
ambiguous place in the section quoted below: it is of course the
long-term memories that are the outcome of a long process initiated by
LTP; "working memory" as in Baddely's original verbal description and
as further defined by Fuster's and Goldman-Rakic's (two different)
operations apear to involve different phenomena, processes, and
anatomical relations than the kind of "working memory" Sturla seems to
be talking about.

(bytheway: has no one besides me read anything but rat literature or
anything since c. 1988? I think even in the rat literature they have
been less keen on the "spatial" intrepertation of hippocampal function
lately; the original model may say more about the kinds of tasks people
use with rats rather than about the hippocampus, even a rat
hippocampus.     more specifically, has anyone read else read anything
by Fuster or by Goldman-Rakic, or any of the human
clinical/experimental studies of "working memory"?  is any one else out
there familiar with Trails B?  given the contrast between the
relatively undeveloped rat "prefrontal" cortex--in the rat it is so
well hidden it was mistaken for the cingulate for many years--and the
profound importance of the prefrontal cortex of higher primates, anyone
discussing "working memory" without a good knowledge of
primate--including human--neuropsychology is not playing with a full
deck.)

Well, back to the points below.

Rather than thinking of some "longterm" memories lasting longer than
others, all the lesion studies and parallel cellular-level studies
suggest it is not fruitful to think of memories starting as "longterm"
but somehow in some cases being "lost"; memories may indeed be "lost"
eventually, but the most fruitful lines of research point to LTP as
merely the STARTING point of a PROCESS memory formation which continues
for weeks, months, years (these being the time-scales of various
retrograde amnesia gradient lab experiments and "experiments of
nature".

F. Frank



In <3512ca28.1765860 at news.ntnu.no> stumol at stud.ntnu.no (Sturla Molden)
writes: 
>
>On 20 Mar 1998 03:49:22 GMT, flefever at ix.netcom.com(F. Frank LeFever)
>wrote:
>
>>LTP has been suggested chiefly as the basis for formation of
long-term
>>memories, not "working memory" in the sense I have emphasized
>>(initiating a process which continues over a rather long period).
>
>LTP has been suggested to be involved in memories that rely on
>neural plasticity rather than dynamic change in neuronal activity.
>This also include some memories that are task-specific and not
>permanently retained. Such memories require continously updating. This
>was what Olton (1985) ment by his working memory view of hippocampal
>function. And it is and operational definition. E.g. you go to the
>store and remember to by a bottle of milk, but two days later it's all
>gone. If Patient HM was to purchase a bottle of milk, he would have
>forgot why he went to the store when he got there. 
>
>I think in these sence, "working memory" is more like an "intermediate
>term memory", enduring but futile. Whether such working-memory has a
>physiological foundation that differs from long-term memories (that
>are not lost, ore are they?) is also an unsettled question.
>Neccesarily, long-term memories are shuttled through a hypothetical
>intermediate-term store (Rawlins' [1985] buffer?), so interfering with
>working-memory also interfer with  long-term memory. There are also an
>interpretational problem with this categorical model of memory. The
>"power-law of memory" from cognitive psychology doesn't yield this
>prediction. My guess is that working-memories in this sence is just
>long-term memories that are lost with a higher rate than the memories
>we term proper "long-term memories". In this sence there are no
>completely permanent memories, memories are just lost at a different
>rate (some very slow). Speaking in favour of the categorical model,
>electroconvulsive therapy also cause some retrograde amnesia, hower,
>this may also be interpretated  in the way that these memories are
>just weaker (the reason why they are lost at a faster rate) and
>therefore more affected by the ECT. An interesting question is what
>modulate(s) the persistance of long-term memories.
>
>The distinction between short-term memories and long-term memories are
>more clear-cut. Short-term memories are dependant on dynamic changes
>in neuronal activity, long-term memories require plasticity. But from
>my point of view, splitting up enduring (plasticity-dependant)
>memories into different classes according to their stored time is a
>conceptual construct that may prove to be devoid of a true
>physiological foundation.
>
>And speaking of memeories, are there any operational definitions of
>"impicite/procedural" and "explicite/declarative" memories? I think
>the common aggreement that "memories we are conscious about are the
>explicite ones" is a bit sloppy, afterall, what does it mean -
>physiologically speaking - to be mentally "conscious" of something? I
>would like to see a definiton that  relate the two forms of memories
>to something that can be objectively measured (in both man and
>animals). I would be grateful if anyone would give me a reference to
>litterature dealing with this  matter in a proper way. 
>
>
>Sturla Molden
>
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