Mike,

on the group level , SPM will only analyze voxels for which data from all subjects is available. So if you have relevant motion, signal dropouts, or spatial normalization inaccuracies, this will explain "border regions" not completely covered on the second level. You could use the spm movie function to check all individual con images going into your analyses.

Cheers,
Marko
[log in to unmask]" class="GroupWiseMessageBody">

 


--
____________________________________________________
Prof. Dr. med. Marko Wilke
 Facharzt für Kinder- und Jugendmedizin
 Leiter, Experimentelle Pädiatrische Neurobildgebung
 Universitäts-Kinderklinik
 Abt. III (Neuropädiatrie)

Marko Wilke, MD, PhD
 Pediatrician
 Head, Experimental Pediatric Neuroimaging
 University Children's Hospital
 Dept. III (Pediatric Neurology)

Hoppe-Seyler-Str. 1
 D - 72076 Tübingen, Germany
 Tel. +49 7071 29-83416
 Fax  +49 7071 29-5473
 [log in to unmask]

 http://www.medizin.uni-tuebingen.de/kinder/epn/
____________________________________________________

>>> Mike <[log in to unmask]> 12/27/16 9:38 AM >>>
Hi,

I used spm8 to analyze fMRI data. After preprocessing, first-level model estimation and contrast setting, I used an uncorrected threshold of p = 1 to let all voxels "activated", and, as expected, I found that each subject's fMRI data completely cover the whole brain.
However, for the group contrast (one-sample t-test to see group mean activation), I also used an uncorrected threshold of p = 1, but I found that the whole brain was not completely covered, although the group activation pattern was nice (see attached figure).
Does anyone know why?

Thanks. Mike