A couple of quick questions, then some thoughts. (1) Are the seeds in the same voxel in all subjects? (2) How big are the seeds? The analysis that you have done is not the typical analysis that others have reported. If you notice, almost all papers use Z-scores as the second level input; rather than the con_ images. To get the Z, you need to convert the t-statistic image to an r-value and then use the fisher Z-transform to get a Z-score. However, it is probably useful also to do the analysis with the con images, although there could be scaling issues. In the past, although not published, I converted to percent signal change to make all the voxels on the same magnitude scale. 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 Office: (773) 406-2464 ===================== This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is intended only for the use of the individual or entity named above. If the reader of the e-mail is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that you are in possession of confidential and privileged information. Any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If you have received this e-mail unintentionally, please immediately notify the sender via telephone at (773) 406-2464 or email. On Thu, May 12, 2011 at 11:31 AM, Cornelia McCormick < [log in to unmask]> wrote: > Dear SPM users, > > I am analyzing resting state data of a group of healthy individuals > with a seed-based approach. In my regression model, I added the > extracted timeseries of the seed voxel as well as a few other > regressors (motion parameters, CSF, WM). The first level analysis > (t-test) shows strong activation in the common default mode areas. > However, when I set up the second level random effects model (all con > files combined in a one-sample t-test), there is no activation left. > No even the seed voxel lights up anymore. There is clearly some > mistake in setting up the second level analysis but I don't know what. > Does anybody have an idea? Any help would be aprreciated! > > Thanks a lot, > Cornelia >