Hello,
cluster-size (p) threshold is determined always according to the actual
distribution of cluster sizes resulted from the cluster-forming (Z)
threshold.
I assume, that your "new" cluster in the prefrontal cortex is larger than the
"old" one in the DLPFC. Most likely, the DLPFC-cluster did not grow much
after setting the Z-threshold lower, but other cluster did and/or lower
Z-threshold resulted in large "new" clusters. Consequently, you "old" cluster
become small in comparison to them and did not become significant.
I hope, it helps,
Auer, Tibor M.D. Ph.D.
Biomedizinische NMR Forschungs GmbH
am Max-Planck Institut für Biophysikalische Chemie
Am Fassberg 11
37077 Göttingen
Germany
Phone/Work: +49-(0)551-201-1725
Phone/Home: +49-(0)551-387-0076
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-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf Of
Johnson Hampson
Sent: Monday, August 20, 2012 7:13 PM
To: [log in to unmask]
Subject: [FSL] Feat higher level help
Hello experts
I ran a FSL dual regression melodic ICA analysis to get FEAT copes and
Varcopes. Now when I run higher level feat analysis, I results are really
strange... My cluster level threshold was z=2.3 and P=0.05 and I saw a nice
dorsolateral prefrontal cortex at p<0.05 (only one cluster). But when I
reduce my threshold to z=1.9 and P=0.05, I cannot see this same DLPFC region,
but I see other clusters in the prefrontal cortex. Can anyone explain why
this might be?
How can I see a region at higher thresholds (z=2.3) but not at lower
thresholds (z=1.9)??
(my Feat version is v5.98)
Thank you for any help!
John
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