replies to replies to a question

James Woodson jwoodson at ucla.edu
Thu Nov 7 20:22:05 EST 1996


>> old *****************

>> The hippocampus is not, I repeat NOT a known locus of "working memory.
>> Individuals like Brenda Milner's classically hippocampal H.M. can remember
>> phone #s, and carry on a relatively coherent conversation with whomever is
>> in the room at the time, therefore, there is NO deficit in working memory.

>ok, if this is what you mean by working memory.

New:  This is the currently accepted definition of working memory.  7 +/- 2
digits/items, occasionally enhanced by "chunking" items into one coherent
group.  Fades fast without constant rehearsal or repetition.  See any up to
date text like those by Pinel, Carlson, or Kandel et. al.

>> Additionally, most olfactory input goes a) directly to olfactory cortex, or
>> b) to the amygdala (not directly to the hippocampus. Furthermore, the
>> hippocampus in both the rat and human is NOT close to the olfactory bulb.
>> It curves around (in the rat) dorsocaudally underneath the cingulate cortex
>> and (in humans) projects down into the temporal lobes.  Perhaps Mr. Blue
>> meant to say the hippocampus in humans is somewhat proximal to the
>> olfactory cortex in the insula, hidden by the temporal lobes.

>yes, proximal

New:   No harm intended, no harm done.

>>  More recent
>> work on the hippocampus (See Kim & Fanselow, 1991) suggests that it is
>> involved in the transition from short term to long term memory known as
>> consolidation,

>this is what I meant by working memory.

New:  Review your terminology:  there is a big difference between working
memory and consolidation.  In addition, there is a big difference between
sensation, perception, acquisition, utilization, consolidation, storage,
and retrieval, all of which are involved in learning and memory.
Generalizations accomplish virtually nothing.

>> which can take from minutes to weeks depending on the
>> complexity of the stimulus or context and of course, on the species
>> involved.
>> To elucidate on the nature of the relative differences in size between the
>> hippocampi in rat and human, the main difference between rat and human does
>> not appear to be in knowledge acquisistion but in ability to both STORE and
>> MANIPULATE knowledge.

>Rats usually out preform humans in mazes.  Since they have more and we
>have less is this then the reason.  I focused on olifaction because this
>is likely to be the MOST important sense they have and use.
>We could at birth destroy the olifactory lobes this may reduce the
>ratio in rats if the hippocampus is heavily involved in memory considation
>for olifaction.

NEW:  Except for the well known fact that rats have about 1000x our sense
of smell, the rest of your above statement is unjustified by empirical
evidence. = Speculation.

>>  Our overgrown cerebral corticies give us just that
>> ability.  The hippocampus is believed NOT to be a locus of memory storage.
>agreed.
>> Rather, it is currently thought to be a processing station or relay, and
>> therefore, may actually serve a lesser role in humans than in less
>> cortically dependent species.

>agreed.  The question remains why is the ratio LARGER for rats?
>What would you guess?  Ron Blue

Ron, Ratios are relative, right?  In comparison to our corticies, rats
hippocampi  are much smaller by several orders of magnitude.  Just as other
subcortical structures can be overridden or circumvented by our cortical
functions which are unavailable (to our knowledge) in other mammals, it may
also be possible that some forms of memory acquisition and consolidation
are hippocamally independent due to our extensive neocortex.  There is
support for this in the learning of implicit or non-declarative tasks by
hippocampal individuals such as H. M.  See work by Larry Squire if you are
interested.


James Woodson* (jwoodson at ucla.edu)
Dept. of Psychology - Behavioral Neuroscience
University of California at Los Angeles
405 Hilgard Ave.
Los Angeles, CA 90095

 "Verbosity leads to unclear, inarticulate things."
                --Vice President Dan Quayle, 11/30/88

*Research in Learned Helplessness, Adenosine,
 Anatomical Sex Differences in the Brain (SDN-POA), and Sexual Motivation

 Standard disclaimer: Las opiniones de este mensaje son
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