Hi All --
We are analyzing data from a multi session study in which we want to
remove the effects of time from our analysis (i.e. perform a t contrast on
conditions of which one occurs later than the other, without seeing
effects simply due to the passage of time, i.e. learning, fatigue, etc.).
WeŽve tried an interaction contrast [-1 -1 0 0 1 1]*[-1 1 -1 1 -1 1]=[1 -1
0 0 -1 1], but are not sure this is what weŽre looking for. Instead of
observing the areas in which our effect was greater in the late condition
than in early, weŽd like to control for these effects. One idea was to
create an F contrast to model the effects of time (i.e. [1 2 3 4 5 6],
calling this "effects of time"), and then run one of our contrasts,
masking exclusively against "effects of time". Would this provide us with
a map of voxels in which our experimental conditions have effect,
excluding properly late vs. early time points? If not, are there other
suggestions as to how to do this?
Thanks very much,
Jamil
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