Dear all,
We have been analyzing a dataset where there was a significant difference
between the reaction times of the two groups in our task (15 in each
group). In an effort to probe the effects of this difference, I added a
new EV with the demeaned reactions times for each subject.
Some interesting between-group blood flow differences disappeared,
indicating that these were related to the reaction time (e.g. the longer
the reaction time, the more blood flow to this area). Some between-group
differences remained the same, indicating these were not related to the
reaction times.
Interestingly, there is now a new area of activation in the between-group
contrast following the addition of the reaction time covariate. We are
trying to understand what this might mean. Does this mean that activity in
this area was negatively correlated with reaction times (the faster the
performance, the more the blood flow)? Or is there some more complicated
relationship?
Thanks,
Dost
|