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Brain surface

John Hasenkam johnh at faraway.hgmp.mrc.ac.uk
Fri Oct 15 06:53:34 EST 2004


"Matthew Kirkcaldie" <m.kirkcaldie at removethis.unsw.edu.au> wrote in message
news:m.kirkcaldie-314C95.10523415102004 at tomahawk.comms.unsw.edu.au...
> In article <416e6482 at dnews.tpgi.com.au>,
>  "John Hasenkam" <johnh at faraway.> wrote:
>
> > It's not justified, it is just a current limitation of the technologies.
> > This is being overcome. It is always good to be aware of such
limitations.
>
> What limitation would that be?  fMRI, for example, can image anywhere in
> the head with equal ease.  The original poster was correct in saying
> that neuroscientists' attention is centred on the cortex, and not for
> technical reasons.
>
> For the original poster: much of the "higher" cognitive abilities are
> thought to be handled by the cerebral cortex, which is the outer surface
> of the brain.  There are plenty of us who are interested in what happens
> in the rest of the nervous system, though.
>
>       Cheers,
>
>          Matthew.

Thanks for the correction Matthew, like the original poster I was under the
impression that fMRI was limited. Perhaps you can help me with another
concern in relation to fMRI. I have noted in a number of articles that
images produced for a given task can vary quite considerably. One study,
which I can no longer find amongst the thousands on my hard disk, even
asserted that the imaging can be affected by steriod levels. Another study,
which I can reference, on language processing across the menstrual cycle,
demonstrated quite striking changes in the various regions, though certain
key regions remain activated, there was a surprising spread and difference
in regional activation across the menstrual cycle. I can provide the
reference and pdf if you like. Would appreciate any comments you have on
these matters because to me, at present, such findings raise interesting
questions regarding localisation and how general physiological changes can
impact on brain activity. This concern was heightened recently when I read
an unpublished paper citing that replicability in PET and fMRI is difficult
to achieve. The author asserted that replicability was all but absent. When
I found his web page he had posted various editor responses and none of
these indicated a challenge to his paper, rather that he needed to do more
work, or it was not appropriate for that particular journal. The only reason
I read this paper is because I had noted this lack of replicability
mentioned in quite a few other papers, though only in passing.

Your opinion on these matters would be appreciated,


John.
ps, hope you get some rain down there soon, here in SE QLD dry as dust ... .






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