Working memory

F. Frank LeFever flefever at ix.netcom.com
Thu Mar 19 22:49:22 EST 1998


In <1998031807310801.CAA15177 at ladder01.news.aol.com> uwilwantme at aol.com
(Uwilwantme) writes: 
>
>Have we forgotten that you cannot completely localize function to ONE
area of
>the brain? 
>
> Also important... the intricate connections of the hippomcampus AND
the
>prefrontal cortex.  If you block NMDA receptors of the hippocampus,
you disrupt
>working memory (yes, Frank, in an animal model...but think about PCP
users;
>Highfield, Nixon, & Amsel, 1996; Behavioral Neuroscience). 


My point is not "animal model" vs. "human model", but about SOME KINDS
of animal models vs. others.  The paradigms typically used with rats
operationally define ONE pheomenon for which people have used the term
"working memory" (cf. my original post oon this subject).  The
paradigms used with monkeys define different phenomenb, for which the
term "working memory" has been used by yet OTHER people.  (e.g. Pat
Goldman-Rakic's paradigms and Joachim Fuster's paradigms)

Take-home lesson: don't get too hung up on words.  A rose is a rose is
a rose, but "working memory" is NOT "working memory".  Only agreement
among OPERATIONAL definitions would let one say that "working memory"
is "working memory".  If  you are not familiar with the term
"operational definition", derived from Percy Bridge's (Bridgman's? my
semantic memory is failing me in my dotage) injunction to physicists
early this century  (in "How to Make our Ideas Clear", I believe), and
long-adopted (but sometimes misunderstood) by psychologists, then this
itself needs too be addressed before we procede further.

I do not think PCP intoxication is a good model in this context (nor is
NMDA signalling exclusively in the hippocampus, for that matter).

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).

As said in an earlier post, "working WITH memory" (Fuster's
restatement, I believe; cf. Baddely's more extended description,
earlier) emphasizes the prefrontal role in TEMPORARY choices among
long-term and immediate memories for USE during execution of a task,
and as such may modulate activity in the hippocampus OR in parietal
cortical association areas.

Frank
NYNG









  NMDA receptors are
>involved in a putative molecular model of learning and memory, LTP. 
Typically,
>when you interfere with LTP, you interfere with memory. 
Interestingly, LTP
>occurs primarily in the hippocampus and most is NMDA receptor
dependent.   I
>don't think you can rule out the involvement of the hippocampus with
the
>molecular  information out there.




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