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Dear SPM/Marsbar Wizards, I am using SPM5 for VBM analysis of structural MRI grey matter density. I have done a correlation with a creativity measure and grey matter density. From my SPM analysis I have 4 clusters in the brain that positively correlated with the creativity measures (p<. 001, threshold of 25) and 4 clusters that negatively correlated (p<. 001, threshold of 25) with the same creativity measures. I then used Marsbar (love the name) to extract ROI (full options) and export the mean voxel value (summary time course for region) for each cluster of each scan. I wanted the mean voxel value for each scan (rather than the peak voxel value that SPM gives) to make a scatter plot with the creativity scores and calculate correlation coefficients. When I do this for my clusters that correlated positively with the creativity scores I get really nice correlations (between 0.7 to 0.62). However, when I plot the mean voxel values for the clusters that correlated negatively, i get really weak correlation coefficients (-. 2 to 0.09). I am wondering how this is possible to get such weak correlation coefficients for the negative correlations by just using the mean of the clusters, when in SPM I am getting these 4 clusters as significantly negatively correlating. I tried using the median instead of the mean in Marsbar, but this did not help. Any thoughts or suggestions as to why this is happening would be greatly appreciated. Merci beaucoup. Julie