What do neurons of the rat hippocampus encode? How do we know this?
Propose an original follow-up experiment to expand on what is
currently known.

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Request for Question Clarification by andrewxmp-ga on 05 Jan 2005 15:04 PST

Hi

I've been working on this answer for an hour or so now, and should
have it completed shortly.  Just a few things- a) the short answer to
the first question is "we don't know what hipocampal neurons encode" 
We just don't.  There are intreaguing leads, however, and I will
describe those in detail.  b) this "original follow up experiment"-
how detailed must this be?  A grant proposal can be a hundred pages,
yet a short overview of the same proposed experiment could be a
paragraph or two.  Please clarify what sort of depth you
require.....otherwise i'm aiming for 1-2 pages approximately.  Thanks.

-Andrewxmp

Rats who perform a maze task will complete the task with greater speed
after increased repetition of the task. Rats with a damaged
hippocampus will not be able to display this ability to learn the task
unless they were trained to complete the task previous to the damage. 
This indicates that the hippocampus is involved in encoding long term
potentiation (LTP).
Researchers at USC have studied slices of rat hippocampus and have
analyzed input signals which ellicit an output and have encoded this
model into a silcon chip.  This chip could potentially mimic the
activity of the hippocampus. A logical followup would be to bypass a
damaged hippocampus of a rat with this chip, hoping to see if the
subject can recover and demostrate new LTP.

It's not a secret as to what the HIPPOCAMPUS does- it is responsible
in encoding memories. I am specifically concerned with single neurons
within the hippocampus.

LTP, a strengthening of synapses between neurons discovered by Bliss
and Lomo, is perhaps the easiest to induce in the hippocampus.
Therefore, researchers use a preparation consisting of slices from the
hippocampus to investigate this phenomenon. The major problem with
this preparation, however, is that it assumes the hippocampus only
transmits information in a 2 dimensional fashion (See Amaral & Witter,
1989). Given the 3 dimensional projections of axons into and within
the hippocampus, a 2 dimensional transmission of information is more
likely to be the majority than the minority (The minority being the
dentate gyrus). Therefore, the answer to what hippocampal neurons
encode is more likely to be found from in vivo work. Also, it is
inappropriate to say "the hippocampus is involved in encoding
long-term potentiation".

I appreciate your attempt to answer the question, but it appears this
topic is beyond your scope of expertise.

I apologize if my answer was below the scope of what you were looking
for.  It was the five second explanation of what five minutes of
googling could scrape up.  Five more minutes scraped up this review on
the hippocampus and neuronal response:
http://www.psych.ubc.ca/~bchristie/PSYC461/Papers/Eichenbaum1999spatial.pdf

Good luck with getting an appropriate and satisfying answer.

I made a mistake....the 2-D transmission of infomation is the MINORITY
(dentate gyrus granule cell projection) not the MAJORITY