Hippocampus - replies to a question

Ron Blue rcb1 at LEX.LCCC.EDU
Thu Nov 7 13:57:51 EST 1996

On 7 Nov 1996, James Woodson wrote:
> >On Thu, 7 Nov 1996, Michelle Lim wrote:
> >> Hi there. I'm new to this newsgroup so please bare with my simplicity. I
> >> have a very basic question that I would like to put forth and perhaps
> >> get some answers. Comparatively speaking, the rat has a larger
> >> hippocampus than us humans - am I right in saying this? If so, why? No
> >> offence to the rat but you would think that humans would have a larger
> >> hippocampus, not only because we are relatively much larger but do we
> >> not have "more" memories to save?
> >>
> >> Michelle
> >A question I would not have normally thought about.  Hummm...
> >Rats main sensory imperative is probably olifaction.  Humans are low
> >on this one.  Hippocampus is probably a mechanism for "working memory"
> >a special type of short term memory.  The hippocampus is close
> >to the olifactory lobe this might be the reason for the relationship.
> >Ron Blue
> NEW*****************
> 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.
> 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
>  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.
> 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.
>  Our overgrown cerebral corticies give us just that
> ability.  The hippocampus is believed NOT to be a locus of memory storage.
> 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
> 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
> personales y no comprometen las dependencias a cargo de la firmante.

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