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The only problem that I could face might be labeling the common areas. Is there anyway of labeling bin maps of 1s?

You can use imcalc to convert the thresholded t-map to 1s and 0s with the equation: i1>0.

When you add the maps together:
Voxels with a value of 1 will have only task effect 1, voxels with a value of 2 will only have task effect 2, voxels with a value of 3 have both tasks effects (aka the conjunction).

 

Is this an accepted way of reporting it?  

Yes.
 

The other two questions that I have are: 

1- can the conjunction analysis be done t the subject level and then do it at a group level?

If you do it at the first-level, there is no way to bring the conjunction map to the group level. You could ask how many subject show the conjunction though.
 

2- if I do a one-sample t-tests of con images that are repeated measurements ( 2 from each subject), can I correct for non sphericity here ?   Would this be correct?

No. It would not be correct. one-sample t-tests can only have 1 image per subject. If you have more than one image per subject you have violated the assumption of the one-sample t-test.


Regards,

AS

On 31 Oct 2013, at 07:21 pm, "MCLAREN, Donald" <[log in to unmask]> wrote:

Aser,

You can't do a conjunction contrast at the group level because SPM can't give you the between-subject effects if you have multiple images per subject in the model. However, if you want to compute the conjunction, you could do 2 one-sample t-tests and then threshold each map, convert the thresholded maps to 1s and zeros, then use imcalc to determine the overlap with the equation: i1+2.*i2. The resulting image will have a value of 3 in any voxel that is common at the group level.

Hope this helps,

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Postdoctoral Research Fellow, GRECC, Bedford VA
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Thu, Oct 31, 2013 at 12:32 PM, fMRI <[log in to unmask]> wrote:
Hello all,

I would like to know how I can do a conjunction analysis at the group level.

I have two contrast images from each subject.

Can I do  conjunction  contrast to see the common effect at the group level? If yes how can I do it practically?

Regards,

Aser