From: Patrick Wilken (patrickw@cs.monash.edu.au)
Date: Wed Nov 18 1998 - 18:02:35 MST
Anders:
Thanks for the clarification. My background is psychology; my main area
being higher-level vision so I certainly am not an expert on the
neuroscience side of things (though of course everyone interested in these
issues is slowly drifting into the vortex of cognitive neuroscience).
>I was thinking in this context of structural change in the sense of
>deviation from normal neural structure (i.e dead neurons), and
>functional change in the sense of deviation of normal function. The
>distinction is admitedly blurred, and might not even be perfect for a
>"wet" system like the brain.
I understand your definition, but isn't it likely to cause confusion? Cell
death is only one extreme end in the spectrum of structural change that
occurs in the brain. All long-term memory formation (and for that matter
forgetting) causes structural change. Chronic drug use obviously causes
structural change (and by your definition is OK to be called that as its
not normal), but long-term mood changes probably cause similar up or down
regulation of specific neurotransmitters. Aren't mood changes part of
normal functioning? Just because the change is occurring at a level we
can't detect doesn't mean that it isn't structural, and it certainly
doesn't mean we won't have the technology to detect such changes in the
future.
>True. But many functional differences do not cause the neurons to
>change noticeably from normal (i.e. I can come to believe that the
>earth is flat; it is a stupid belief and corresponds to some changes
>in my synaptic connections, but no neurons need to die for me to think
>it).
Sure you are going to see some quick and very reversable changes in brain
structure (e.g. my belief the traffic light is red), but this doesn't mean
long-term structural change is not part of normal brain function. For
instance Nikos Logothesis has done nice work training up macaques on unique
wireframe objects (basically distorted coathangers). He finds that in
infereotemporal cortex (IT) that, just like the infamous face cells
detected there, the macaques develop wireframe coathanger cells. This is
not just a functional change, but a long-term structural change in the part
of the brain associated with object recognition.
best, patrick
-------------------------------------------------------------------------
Patrick Wilken http://www.csse.monash.edu.au/~patrickw/
Editor: PSYCHE: An International Journal of Research on Consciousness
Secretary: The Association for the Scientific Study of Consciousness
http://psyche.cs.monash.edu.au/ http://www.phil.vt.edu/ASSC/
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