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Hi Freesurfer experts,
I’m running a simple qdec analysis to examine group differences in surface measures between a patient and control group, controlling for age and TBV.
I noticed that when I run Monte Carlo Simulations (threshold=1.3, sign=abs), I get the following output in my terminal window:
~~~~~~~~~~~~
# ClusterNo Max VtxMax Size(mm^2) TalX TalY TalZ CWP CWPLow CWPHi NVtxs Annot
1 7.365 125481 2114.03 -34.4 4.1 1.6 0.01660 0.01500 0.01820 4933 insula
2 3.851 73048 1830.45 -8.4 30.1 29.4 0.03440 0.03210 0.03670 3210 superiorfrontal
3 -3.248 128137 4923.73 -8.1 -64.0 5.8 0.00010 0.00000 0.00020 7680 lingual
Simulation complete. ~~~~~~~~~~~~
However, when I click on “Find clusters and go to max”, the output in my terminal window changes to be as follows:
~~~~~~~~~~~~
Generating cluster stats using min threshold of 1.3...
Found 3 clusters
Contrast: 'lh-Diff-Control-Klinefelter-Intercept-volume', 20fwhm, DOF: 35
ClusterNo Max VtxMax Size(mm2) TalX TalY TalZ NVtxs Annotation
--------- --- ------ --------- ---- ---- ---- ----- ----------
1 -4.0000 33 4923.73 -12.0 -67.1 34.7 7680 precuneus
2 1.7799 9 2114.03 -26.3 23.8 -6.0 4933 lateralorbitofrontal
3 1.4634 21 1830.45 -6.6 33.8 49.8 3210 superiorfrontal ~~~~~~~~~~~~
Lastly, I see that the x/y/z coordinates of the peak coordinates listed above are on the very edge of the corrected cluster. Yet, visual inspection of the peaks from uncorrected significance maps suggest that the peaks it is quite far from the “hottest” parts of the uncorrected significance maps.
My questions are:
1. Why are these values different, and what values should I report? 2. Are the peaks listed above the center of gravity? Or highest p value of the cluster? Curious as to why the heatmap values are so different from the values above.
Many thanks, Lara