Thank you Donald. I am curious what you (or others) think of the
approach of creating minimum beta value images at the first level and
then doing a one-sample t-test on those images. Would this be a method
for testing the conjunction of effects at the second-level?
-------------------------------------------------------------------------------
Bob Spunt
Postdoctoral Fellow
Social Cognitive and Affective Neuroscience Labs
Department of Psychology
University of California, Los Angeles
That process is correct.
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
=====================
On Mon, Feb 27, 2012 at 3:32 PM, Bob Spunt <[log in to unmask]> wrote:
> Dear SPM experts,
>
> I apologize if I missed this on previous posts to the listserv, but I have a
> quick question regarding testing the conjunction of the parameter estimates
> (i.e., condition effects implicitly compared to baseline) at the second
> level. Assume I've estimated the effect of two conditions, A and B, for
> every subject at level. Is the following procedure valid?
>
> 1. Run one-sample t-tests on the parameter estimates for A and B for the
> group and compute the spmT images for the positive effect.
> 2. Compute a minimum statistic image from the spmT images for the one-sample
> t-tests for A and B (which includes the minimum statistic value at each
> pixel).
> 3. Draw inferences from the thresholded minT image.
>
> On a related point, I have used Donald McLaren's approach to create binary
> images for each subject separately, then sum these images to get an image
> representing the proportion of the group showing the conjunction effect.
> However, this method does not permit an inferential test. Would an
> alternative method involve computing minimum contrast images for each
> subject and then taking those images up to the second level?
>
> Thanks for any tips!
>
> Bob
>
> -------------------------------------------------------------------------------
> Bob Spunt
> Postdoctoral Fellow
> Social Cognitive and Affective Neuroscience Labs
> Department of Psychology
> University of California, Los Angeles
>
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