function of hippocampus

[Randall C. O'Reilly]

Ken Miller <ken at phy.ucsf.EDU> writes:
> With respect to recent postings about models of hippocampus and
> memory, I'd like to toss in a cautionary note.  A recent report
> (Elisabeth A. Murray and Mortimer Mishkin, "Object Recognition and
> Location Memory in Monkeys with Excitotoxic Lesions of the Amygdala
> and Hippocampus", J. Neuroscience, August 15, 1998, 18(16):6568-6582)
> finds no deficit in tasks involving visual recognition memory or
> spatial memory with lesions of hippocampus and amygdala.  Instead,
> deficits in both cases are associated with, and only with, lesion of
> the overlying rhinal cortex.

One general take on the division of labor between the rhinal cortex
and the hippocampus proper is that the rhinal cortex can subserve
"familiarity" based tasks (e.g., recognition), and the hippocampus is
only necessary for actually recalling information.  Familiarity might
be subserved by priming-like, small weight changes that shift the
relative balance of recently-activated representations.  In contrast,
the hippocampus proper seems particularly well suited for doing
pattern completion, where a cue triggers the recall (completion) of a
previously stored pattern.  This requires storing a conjunctive
representation that binds together all the elements of an event (so as
to be recalled with a partial cue).  Both familiarity and recollection
can contribute to recognition memory, but having just familiarity can
presumably get you pretty far.  There is a growing literature that
generally supports this distinction, some refs included below.  I
can't comment as to how this relates to spatial navigation.

				- Randy

@article{Yonelinas97,
  author    = {Yonelinas, A. P.},
  title     = {Recognition memory {ROCs} for item and
    associative information:  The contribution of recollection and
    familiarity.},
  journal   = {Memory and Cognition},
  pages     = {747-763},
  year      = {1997},
  volume    = {25}
}

Aggleton & Brown, in press.  Episodic Memory, Amnesia, and the
Hippocampal-Anterior Thalamic Axis.  Behavioral Brain Sciences,
(penultimate draft available from BBS ftp site).

@incollection{OReillyNormanMcClelland98,
  author    = {O'Reilly, R. C. and Norman, K. A. and McClelland, J. L.},
  editor    = {Jordan, M. I. and Kearns, M. J. and Solla, S. A.},
  title     = {A Hippocampal Model of Recognition Memory},
  booktitle = {Advances in Neural Information Processing Systems 10},
  year      = {1998},
  publisher = {MIT Press},
  address   = {Cambridge, MA}
}

this is available as: ftp://grey.colorado.edu/pub/oreilly/papers/hip_rm_nips.ps

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