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> I ran VBM analysis for Grey matter for some subjects but in the MSU print > out of the activated clusters it shows a lot of white matter activation. > Now I only ran grey matter segments so I dont understand why the MSU is > showing a lot of white matter. Could anyone help me on that. The t statistic is proportional to the ratio of the mean difference between the groups, to the square root of the residual sum of squares. Even if the region of maximum difference is right in the middle of the grey matter, this implies that the blobs tend to shift slightly towards regions of lower residual variance. Grey matter has higher variance, leading to the blobs shifting slightly towards non grey matter regions. Take a look at the con image and ResSS images for a clearer idea of the cause. Best regards, -John