Dear List:
Our question is how to use a parametric modulation analysis to
examine the relationship between a physiological variable (blood
pressure) and BOLD activation while also taking into account the
effects of our experimental conditions.
Our design involves 3 conditions: A resting state, an easy task and
a difficult task. We obtain one measure of blood pressure for each
condition.
We can analyze the data to provide condition related effects (hard
task versus easy task, or rest, or other combination) and we can
analyze the data to provide the overall effects of blood pressure by
using blood pressure as a parametric modulator of the BOLD response
across conditions. We can mask the results of this parametric
modulation analysis with the results of our condition analysis,
which we believe will reveal those brain regions in which BOLD
activation is uniquely related to blood pressure, but not to the
basic effects of condition.
What we really want to do, however, is find a means of describing
the task by parametric interaction (somewhat like a conditions and
covariates analysis with PET where the covariate is allowed to
interact with condition). How do we do this and is this even a
sensible question?
Many thanks,
Pete, Stuart and Lena.
UPMC MR Research Center
PUH B-804
200 Lothrop Street
Pittsburgh
PA 15213
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