Hippocampus - a question

G K GRAY gord at homostudy.win-uk.net
Sun Nov 10 17:41:49 EST 1996

In article <56013i$bc9 at news.ycc.yale.edu>, A J Harrington (apence at pantheon.yale.edu) writes:
>Ron Blue (rcb1 at LEX.LCCC.EDU) 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? - snip
>: > 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
>Working memory is mediated through the prefrontal cortex, not the
>hippocampus, although the areas are connected.  The hippocampus is usually
>thought of as the mechanism for storing memories.

There appears to be some doubt here!

>As to the original question, while the rat hippocampus is *relatively*
>larger, the human hippocampus is _much_ larger by actual volume than the
>rodent version.  Differences in relative size are due to the dramatic
>increase in cortical volume in primates.  An even more dramatic example of
>this is the basal ganglia.  In rat brain coronal sections, the
>caudate-putamen looks like it takes up almost the whole brain.  But that's
>simply because the cortical areas aren't well developed.

        When, at least 40 years ago, computer developers hijacked
the term "memory", applying it to wired-in hardware - not to the
*information contained therein*, they left the door open for decades
of confusion in brain science. This was adding injury to insult
(not vice-versa!) so we are still facing the task of recovering
lost ground. 
        Only now are we recognising structure and function in orders
of memory. For example, Zeki and others are showing that in the
visual and auditory systems there are separate cortical areas
devoted to separate reporting of stasis and rapid movement - e.g. 
V1 and V5 respectively. However, we still do not know any principle
that tells us precisely how the initial distinction is made in
either system between "stasis" on the one handm and movement that
may be life-threatening on the other. What physical principle(s)
could be involved in distinguishing between threat and innocence in
the enviroment? 
        Mandie's contribution, while very informative, does not
concern this issue.

Cheers! Gord 

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