Dear David,
Saying it another way: The temporal dynamics of the network of neuronal
activation will be confounded with the hemodynamic delay. And of course
this hemodynamic delay is probably regionally different for very
non-neuronal reasons, so one must be careful in making conclusions based
upon timing. Like Thomas Nichols, I've also found delay differences upto
and even greater than 5 seconds within an individual for a simple
event-related visual task (there are also shape differences). In addition,
the temporal dynamics can change significantly within the same "run".
These results are written up in two papers if you're interested (although
these papers are very methods focused and the emphasis is on signal
processing).
Cheers,
Vince
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Vince D. Calhoun, MA, MS, PhD Student (UMBC), Research Engineer
WORK: Johns Hopkins Medical Institutions, Psychiatric Neuro-Imaging
600 N. Wolfe St., Meyer 3-166, Baltimore, MD 21287-7362
VOICE: (410) 955-7861, FAX: (410) 614-3676
WWW: http://www.welch.jhu.edu/~vcalhoun
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"An author [or researcher] should never conceive himself as bringing into
existence beauty or wisdom which did not exist before, but simply and
solely as trying to embody in terms of his own art some reflection of
eternal Beauty and Wisdom...And always, of every idea and of every
method the Christian will ask not, 'Is it mine?' but 'Is it good?", CS Lewis
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