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Deja vu

F. Frank LeFever flefever at ix.netcom.com
Sat Feb 27 12:44:40 EST 1999


One of these days, I'll bring home proper citation for my comments in
Int. J. Neuroscience (c. 5 yrs ago?), summarizing Mortimer Mishkin's
talk in a NYNG conference I had organized.  Among other things,
discussed two-way comounication in cortical streams carrying input from
visual cortex to hippocampus, and back out again to posterior
association cortex, problem of distinguishing between current percepts,
hallucinations, and vivid memories.

In that context, cited Hughlings Jackson's descriptions of "uncinate
fits", i.e. seizures arising in the uncus, with "dreamy states"
sometimes involving aberrations in the sense of familiarity--not only
dlefal vu, but also jamais vu (things well-known to you which "feel"
unfamiliar, strange).

Usually, the problem is put in terms of a specific event which seems to
be re-experienced, because of the strong sense of familiarity each
detail of the event SEEMS to evoke.

I emphasize "seems to evoke", because one of his footnotes reports a
very articulate and thoughtful patient who describes a very strong
sense of familiarity, but--of what, he did not know.

I think this is an important clue.  My belief is that coincidence
between current events and previously experienced events provides a
necessary and sufficient signal for the uncus to "excrete" a sense of
familiarity.  Given the numerous ways in which thresholds can be biased
in the nervous system, the uncus may be too ready or not ready enough
to "excrete" familiarity in a given situation; given multiple
possibilities for "short-circuits" and aberrant signals, its
"excretion" may become dissociated from normal recognition processes.

Given the human mind's incessant need to make sense of experience, it
is not surprising that an aberrant/dissociated sense of familiarity is
asscribed to whatever else is happening: the experience is rationalized
as "this has happened before"; and more sophisticated arguments
(invoking Einstein at times) follow...

F. Frank LeFever, Ph.D.
New York Neuropsychology Group













In <36D73CA3.530F at uswest.net> "David B. Held" <dheld at uswest.net>
writes: 
>
>Howdy,
>
>	Perhaps this is another dead horse that has been senselessly
beaten
>here, but are there any neurophysiological explanations for deja vu? 
>I've heard theories ranging from the somewhat plausible: Event is
>anomalously stored in LTM rapidly, thus creating the sensation of
>familiarity, as it accesses the instant "memory"; to the
>not-so-plausible: Deja vu is experienced when your timeline loops onto
>itself, and touches a different temporal point, giving your mind
access
>to information from that time.
>	Does the first explanation have any truth to it, or is there a
better
>explanation?
>
>Dave
>
>-- 
>David Held, Chief Programmer   "As far as the laws of mathematics
refer
>Business Computing Solutions    to reality, they  are not  certain;
and
>email: dheld at uswest.net         as far as they are certain, they do
not
>web: www.uswest.net/~dheld      refer to  reality."  -  Albert
Einstein




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