Hello! I have the same problem than previously reported in 2002 (see mail
below). I would appreciate any advice how to handle the problem
Thanks
nadine
>> We have been examining the mask.img produced from a second level random
>> effects analysis (one-sample t-test) across 14 subjects. We find it a
bit
>> alarming to see that the mask.img falls well within the perimeter of the
>> MNI template brains in all 3 dimensions. We suspected that this results
>> from variation across the individual 14 subject mask.imgs created at the
>> first level analysis, which in turn results from variation in the
>> normalization to the template EPI brain across subjects. Confirming
this,
>> when we overlay the individual subject mask.img images, there are small
>> variations between subjects in the perimeter or edge of the brain,
visible
>> in all planes.
>>
>> Since the mask.img created at the second level analysis comprises the
>> intersection of all of the individual subject masks, the result is group
>> mask that is smaller than the most of the individual masks and is also
>> smaller than the template. The concern is that the second level
analysis
>> masks out a significant layer of cortical gray matter because of this
>> cross-subject variation."
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