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Deja vu

Nick Medford nick at hermit0.demon.co.uk
Sat Feb 27 13:04:40 EST 1999

In article <36d80278 at news3.us.ibm.net>, Sergio Navega <snavega at ibm.net>
>David B. Held wrote in message <36D73CA3.530F at uswest.net>...
>> Perhaps this is another dead horse that has been senselessly beaten
>>here, but are there any neurophysiological explanations for deja vu?
>Glad to see you concerned with neuroscience! I've seen some of your
>thoughtful posts in comp.ai.philosophy (some months ago we were
>discussing about inductive forms of reasoning) and I had agreed with
>your comments.
>In my vision, Deja Vu is just another illusion. The main point is that
>one of the important activities of our brain is to reduce the
>complexity of what we sense. If I ask you to draw an apple, you will
>not draw yesterday's exemplar, nor the one you ate last week. You
>will probably draw a copy of an internal "model", a categorized
>concept that your brain have, trying to join most of the relevant
>aspects of what you think it is to be an apple.
>In this regard, most of what we perceive is "stored" using such
>"stylized" representations. We do that not only regarding objects,
>but also situations. Roger Schank proposed models in which we
>store "scripts" of several daily situations. While his model may
>need some modernization, I agree that much of our vision of the
>world is represented stories drawn upon high-level invariants
>(cf. Gibson).
>This is what I see as the root of Deja Vu. There are so many
>situations in our life in which we *recognize* high-level aspects
>that match so well with previous experiences that we "feel"
>like living that moment again. It is, obviously, an illusion.
>So far, this is cognitive psychology. As for neuroscience, I'm
>not sure. I guess one way or another neuroscientists will have
>to explain what cognitive science discovers and then we will
>obtain a grounded explanation for Deja Vu and many other
>Sergio Navega.
This is ingenious, but I don't really buy it. At least, while I can see
that this might explain *some* deja-vu experiences, I can't believe it's
the whole story, since these experiences often occur in association with
other neuropsychiatric phenomena like olfactory and gustatory
hallucinations, or motor disturbances (eg stereotypies). I'm referring
particularly to complex partial seizures here. Moreover there are
definite neurophysiological (EEG) abnormalities associated with such
attacks. It's hard to see how your model can explain deja-vu in these

Since such attacks usually affect temporal lobe structures involved in
memory storage and retrieval, it's not surprising that memory
disturbances should be a feature, but I've not seen a truly convincing
explanatory cognitive model of such disturbances. I'd be delighted if
someone could direct me to one, since this is a fascinating area.

Nick Medford

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