Hippocampal role in working memory?

Kevin Spencer kspence1 at uiuc.edu
Mon Jan 26 15:42:14 EST 1998

"Working memory" is a very nebulous concept, and for it to have any
useful meaning, it needs to be rigorously defined.  I imagine that 20/20
didn't try to define working memory.  As for HM, as I remember, his
short-term memory was intact as defined by digit span.  But if he
wasn't allowed to rehearse information, he forgot it very quickly, much
more quickly than neurologically-healthy people would.  So I think it's
accurate to say that HM had a "working memory" deficit, related to
his hippocampal damage.

I know of some evidence for a hippocampal role in working memory
in the human event-related brain potential (ERP) literature.  Intra-
cranial recordings from several labs (McCarthy, Halgren, and others)
has shown that an ERP similar to the scalp-recorded P300 component
is generated in the hippocampus.  The P300 is thought to be related
to a "context-updating" function involved in working memory.  A
hippocampal analog of a similar component, the "novelty P3", has
also been found.  And in addition, Knight has found that people with
damage to the posterior hippocampus don't have scalp-recorded
novelty P3s.

Kevin Spencer
Cognitive Psychophysiology Laboratory
Dept. of Psychology and Beckman Institute
University of Illinois at Urbana-Champaign
kspencer at s.psych.uiuc.edu

Jeremy Leipzig <jeremyl at mindspring.com> wrote in article
<34CB97D8.41E8143A at mindspring.com>...
>     A few weeks ago there was a spot on 20/20 which discussed the
> effects of aging on working memory.  The experts they interviewed were
> claiming that a progressive degeneration of the hippocampus was
> responsible for declines in working memory.
>     I've always understood that the hippocampus was only involved in
> consolidation - or transfer into long term memory.  My undergrad
> neuroscience textbook also states that the ubiquitous ex-hippocampal
> patient H.M.'s short-term memory was "intact."  H.M. suffered from
> anterograde amnesia, specifically in declarative memory.
>     What are your thoughts on this matter?
> --
> Jeremy Leipzig         http://www.mindspring.com/~jeremyl       
> (919)469-0936
> 1204 Kilmory Dr. Cary, NC 27511                        
> jeremyl at mindspring.com

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