I'm trying to use temporal derivatives with hrf in an event-related
analysis but am having trouble figuring out how to code the contrasts
correctly. If there are two event types then there will be four different
covariates. Which of the four are the temporal derivatives? I looked
through the documentation and the matlab code but the answer was not
evident to me. In the archives, an FIL answer posted on 10/28/98 regarding
temporal derivatives says that "a contrast of [0 1 0 -1] for two different
event-types can be interpreted as a difference in HR onset for the two
event-types" which implies to me that the order is cond1 deriv1 cond2
deriv2 since if the order was cond1 cond2 deriv1 deriv2 then this contrast
would involve only condition 2 and its derivative. However, in a message
on 4/28/97 regarding temporal derivatives it was stated that the order is
cond1 cond2 deriv1 deriv2.
Which is it? Or does this mean that the order is different for
event-related analyses and conventional analyses? I am very confused and
getting this wrong would have unfortunate results to say the least. Thank
you very much for your help.
Joe
--------------------------------------------------------------------------------
Center for Neuroscience
1544 Newton Ct.
University of California
Davis, CA 95616
Phone: 530-757-8865
Fax: 530-757-8827
E-mail:[log in to unmask]
www: http://neuroscience.ucdavis.edu/dien/
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|