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Deja vu

Nick Medford nick at hermit0.demon.co.uk
Sat Feb 27 13:19:12 EST 1999

In article <7b9au8$bhl at dfw-ixnews4.ix.netcom.com>, F. Frank LeFever
<flefever at ix.netcom.com> writes
>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 point. Clinically the deja-vu experience
often has this "elusive" quality. Furthermore some of the odd feelings
associated with epileptic "auras", while not usually classified as deja-
vu, have this kind of feel to them.
>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.
As a neurocognitive model this is certainly more plausible- or more
refined,perhaps- than Sergio's idea. Seems to allow for deja-vu in both
epileptic and normal brain states. But what does "excreting familiarity"
really mean?! Do you have any refs on possible neurochemical substrates
for this?
>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>
>>      Perhaps this is another dead horse that has been senselessly
>>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
>>to information from that time.
>>      Does the first explanation have any truth to it, or is there a
>>David Held, Chief Programmer   "As far as the laws of mathematics
>>Business Computing Solutions    to reality, they  are not  certain;
>>email: dheld at uswest.net         as far as they are certain, they do
>>web: www.uswest.net/~dheld      refer to  reality."  -  Albert

Nick Medford

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