sturla.molden at svt.ntnu.no -- delete this (Sturla Molden) writes:
> >Certainly there are many situations where amnesics show no conscious
> >recollection of a previous experience but still show strong implicit
> >effects on their behavior.
>> I personally hate the term "conscious recollection" as it has no
> operational definition. In most instances "conscious recollection"
> means "verbally reporting", as pointed out by Case Wanderwolf in a
> review paper in Biobehavioral and Neuroscience Reviews (I don't have
> the exact reference in my head, but I can look it up). That a human
> can "recollect something consciously" means that it can give a verbal
> report of the event. The question is whether something has to be
> verbally reportable in order to be conscious. Try e.g. to describe a
> particular odour. How does a perfume smell? This task is extreemely
> difficult, nevertheless few would argue that olfaction is
> "unconscious". And what about aniamls and aphasics, are they all
> "zombies"?
Well, in this case I would be quite happy to accept "verbal reporting"
as an operational definition -- it's what I had in mind anyway. The
simplest operational distinction between explicit and implicit memory
is that explicit memories can be probed verbally (though this isn't
quite the way Larry Squire puts it).
I don't think, incidentally, that the odor example is actually all
that strong. If an odor is conscious but indescribable, a human
subject would say, "Yes, I smell something, but I can't describe it."
If the odor is not conscious, the subject would say, "Odor? I don't
smell any odor!" There is a clear difference.
Anyway, the essential point is that there are many examples of
amnesics responding to questions by professing ignorance but showing
by their behaviors that they have retained some traces of the
experience.
> I am personally sceptical to the entire concept of "memory".
> There is no organ that taskes care of sensing, nor are there any
> organ that take care or perceiving. Common knowledge for any zoologist
> is that evolution doesn't produce general purpose mechanisms, it
> produces specialized solutions to particular problems. I think
> nauroscientists should begin to listen to zoologists like Rüdiger
> Wehner and cognitive psychologists like Randy Gallistel who have been
> pointing this out at various occations. I am convinced that evolution
> did not produce the hippocampus for the sake of recollecting
> consciously. Rather, it did probably had something to do with solving
> a particular ecological problem, that is, achieving a goal by
> processing a particular type of information in a particular manner. So
> hippocampal models should emphasise information processing and
> descision making ther than conscious recollection.
I agree with substantial portions of this but you are certainly
overstating the case with regard to general mechanisms. Take, as one
of many possible examples, the mechanism of synaptic transmission,
which is much the same, all the way down to the molecular level, in
every part of the brain and in species ranging from planaria to
hominids. The most dramatic example of a general-purpose mechanism,
perhaps, is the use of DNA to encode the structure of all of the
proteins that are used anywhere in the body. Less impressively, but
more to the point, the neocortex seems to maintain a similar
architecture across areas whose functional roles differ quite widely.
It would be reasonable, then, for there to be a general neocortical
mechanism of long-term memory that would apply across a variety of
cognitive domains.
Of course I agree with you that the hippocampus did not evolve for the
sake of producing conscious recollection. I do, however, think that:
1) there is a distinctive type of memory called episodic memory, which
can be defined operationally; 2) there is reason to believe that
the acquisition of new episodic memories requires a functioning
hippocampus.
-- Bill
