May I ask help with operational details in SPM2?
Two groups of subjects were each studied twice over time, and the
fMRI data were analyzed with standard RFX methods. We are able to
examine the change over time in each group, with either paired
t-testing or Imcalc [i2-i1] approaches.
The goal is to determine whether the change in one group is different
from the change in a second group. The crux of the Q is that change
is examined in a 2-tailed way, could be up or down.
We approached the goal by comparing the [i2-i1 maps], by group, using
a 2-sample t-test. However, significant activation present in maps
generated with this approach could indicate that the first group had
relatively greater increase over time, or it could indicate that the
second group had relatively greater decrease over time.
What steps would one take in SPM2 to disentangle these two
possibilities? Thanks,
Steve
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