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Dear SPM Users and Authors: I still have not heard back from anyone regarding my message from March 30, so I thought I would reiterate my problem and ask if anyone else has ever tried viewing the images which SPM performs its statistics on and whether or not they found the same random patterns of zeros as I did. I tried for the first time recently to use the "generate normalized image data" option in SPM which should allow me to generate and save the images resulting from the application of the global normalization, scaling and gray matter threshold (in the statistics portion of SPM). I used a multi-subject, different conditions (PET) design type with 6 subjects and 2 conditions each (a drug and a placebo). I used proportional scaling with a gray matter threshold of 0.8 and an uncorrected F threshold of 0.99. Upon viewing the resulting PET images, I discovered that they showed a random pattern of voxels throughout the brain with values of zero, having no relation to white or gray matter areas. These patterns were the same for every one of the images generated (even across subjects). The realigned, normalized and smoothed (at FWHM of 12x12x12) PET images I entered into my design matrix had no such pattern/problem. Once again I ask if anyone has observed such a phenomenon before and whether anyone would know the cause. I am concerned as I am not sure why such patterns would be generated and how SPM statistics would handle these random zeros when performing its analyses. I would be more than happy to ftp my pre and/or post statistical analysis images to anyone who would be willing to take a look at them. Thank you in advance for your help, Leann Kinnunen Department of Psychology University of Chicago %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%