Anders:
>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/