# Difference in 2nd-level contrasts

I have a repetition suppression / enhancement study. Alternating video stimuli are presented as follows:

A B A B

I compare the first and last presentations to measure the suppression or enhancement effect. Like so:

``````#       A  B  A  B
C1  = ' 1  0  0 -1'
C2  = '-1  0  0  1'
``````

So the T-image of C1 shows suppression effects, and the T-image of C2 shows enhancement effects.

Now what I would like to do is see where these two T-images differ.

One way I could do this is to binarize the thresholded images, then do a boolean exclusive-or of the two. Voxels that are different between the two will be true, and voxels that are equal will be false.
Is this an appropriate way to do this?
Is there a better way?

Thanks

Given that C2 = - C1, the two images will be exact opposite of each other, so they should not have any positive voxel in common.
Best,
Bertrand

You’re right!
I’ve been looking at the T-images of them both, which are different.
Thanks!