synaptic plasticity question, etc.

Mark Mattson mpm at seqanal.mi.uky.edu
Thu Jan 27 10:11:30 EST 1994


BARRY MANOR, NO DOUBT. (exb0405 at csdvax.csd.unsw.edu.au) wrote:
: Something I'm curious about.  During the course of the adult lifetime, say even
: from minute to minute, does synaptic topography change dynamically ?  Are
: synapses 'broken' and formed as part of normal ongoing brain function ?

: When speaking of 'protien systhe{is' as a basis for some aspects of memory,
: what exactly is meant ?  

: Now my 20 cents worth.  I agree that we've really got to get away from this
: reductionist stuff when studying the brain- comparisons with digital computers
: have got to stop !  I believe that due to the inherent compexity of this organ,
: the massively parallel dynamically adaptve processing for which our information
: theory lags so sadly (behind digital info theory), we will not ever be able to
: describe brain function in reductionistic terms.  One way perhaps todescribe
: brain function would be to build a 'brain' (whatever the technology) that
: becomes self-aware and is able to learn for itself.  This way we could make use
: of the fact that for parallel networks we do not have to fully understand the
: 'structure' underlying the information processing (cf. serial systems,  i.e.
: algorithms).  I mean, how can we ever hope to describe something which employs
: 10E11 neurons and 10E12 connections ?  Time for a paradigm shift.

To answer your questions: Yes, most evidence suggests that we are constantly
changing our synapses.  This is certainly a part of some kinds of learning
(particularly, motor learning) and may also be happening in response to cell
death which destroys existing circuits.  And for your second question, when
people talk about protein synthesis being involved in memory, they typically
are searching for a theory to explain the persistence of memory over long
(on a cellular scale) time periods.  Early LTP theorists often proposed that 
any changes that form the physiological correlates of longterm memory must 
involve changes in the cells' phenotype through alterations in the complement
of proteins being expressed, i.e., some new genetic program of expression.
This idea waned over the last decade or so but saw some revival when Curran
and others noticed that the transcription factor fos is induced under 
conditions which generate LTP.

Also, I agree with your bashing of reductionist modeling.  You might feel
justified when you read about the ideas espoused by Gerald Edelman at the
"What is Life" meeting in Dublin (Sept. '93) described in an article ("What
Are We?...") in the January '94 issue of Science.

Best regards,
Steven W. Barger, Ph.D.
Sanders-Brown Center on Aging



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