The Max is somewhat unrelated to the CWP. The Max is the vertex-wise
maximum and is bounded below by the vertex-wise threshold. The CWP
(cluster-wise p-value) which is derived from the size of the cluster,
the smoothness, and the size of the search space. It is not necessary
for the CWP to be greater than the Max (and often is not).
I've always found p's or (-log10(p)) to be more useful because it is the
actual false-positive rate, which is the number you want for
thresholding (and I have not memorized a z->p transform:). I have a
matlab routine that will convert from p to z (fast_p2z.m).
doug
Siddharth Srivastava wrote:
The max is the -log10(p), bounded below by -log10(CWP) for positive
correlations Hence with an -log10(CWP) of 4, the Max
will be greater than 4, and will specify the maximum -log10(p) value
in that cluster, occuring at VtxMax
Is this right for -log10(p) kind if input? This is how i have been
interpreting my results so far, and i just want
to be sure......
I was also wondering why -log10(p) transformation has been used for
this kind of visualization? SPM displays
SPM_{z} scores, and that seems a better way to report the spms. Is
-log10(p) an approximation to z-scores ?
sid.
On Thu, Jun 4, 2009 at 9:53 AM, Judith Segall <jseg...@mrn.org
<mailto:jseg...@mrn.org>> wrote:
Thanks, for you responses Doug and Pratap. But, both of your
responses need more clarification, because I believe that we are
not all referring to the same 'max'.
Doug:
I understand that when I display the sig.cluster.mgh that the a
CWP value of 0.0001 would be displayed as a 4 by the color bar in
tksurfer, since it is the -log10(p). However, in this case, which
is about the cluster growing summary, the -log10(p) of the CWP
does not equal the Max. Max is -3.312 and the CWP is 0.08250. Or
an additional example form another sig.cluster.summary, where the
Max is -4.310 and the CWP is 0.0192.
ClusterNo Max VtxMax Size(mm^2) TalX TalY TalZ
CWP CWPLow CWPHi NVtxs Annot
1 -4.310 40526 376.78 -12.0 -66.1
5.4 0.01920 0.01750 0.02100 706 lingual
In Pratap's email his answer to my question of what is the max in
the CWP is, "Yes thickness. The MAX indicates the maximum
-log10(pvalue) in that cluster." Which, is stating that it is both
the thickness and the pvalue. I really think that it is thickness
measure, but need some clarification from mgh.
So, is the Max in column 2 of the cluster growing summary report,
from monte carlo simulations, thickness?
Thanks,
Judith S.
On Thu, Jun 4, 2009 at 9:25 AM, Douglas N Greve
<gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu>> wrote:
It will be whatever you used as input. In this case, it is the
-log10(p) value of the maximum in the cluster (not the
thickness value).
doug
Pratap Kunwar wrote:
Hi Judith,
Yes thickness. The MAX indicates the maximum
-log10(pvalue) in that cluster.
Hi all. After looking over our monte-carlo results, I
a simple question
about the sig.cluster.summary output.
Is the " Max" in column 2 below a measurement of
thickness?
thickness, is the correct interpretation the
following: the most
significant
cluster is in the laterorbitofrontal region.
yes at lateral orbital frontal.
The max vertex in that
cluster
has an average thickness of 3.312 mm and the negative
directionality
indicates that it is thinner in that region than in
the fsaverage (from
freesufer) used in the group analysis/simulations?
yes you are correct.
If it does not refer to thickness, is it a statistic, etc?
# Minimum Threshold 2
# Maximum Threshold infinity
# Threshold Sign abs
# AdjustThreshWhenOneTail 1
# Area Threshold 0 mm^2
# CSD thresh 2.000000
# CSD nreps 10000
# CSD simtype mc-z
# CSD contrast lh-Avg-thickness-CAQ-CCI
# CSD confint 90.000000
# Overall max 2.05497 at vertex 92846
# Overall min -3.3122 at vertex 60632
# NClusters 11
# Total Cortical Surface Area 65416.6 (mm^2)
# FixMNI = 1
#
# ClusterNo Max VtxMax Size(mm^2) TalX TalY
TalZ CWP
CWPLow CWPHi NVtxs Annot
1 -3.312 60632 278.00 -15.2 47.7
-15.4 0.08250
0.07900 0.08600 341 lateralorbitofrontal
2 -3.231 51202 118.54 -39.5 24.9
16.9 0.53620
0.52980 0.54260 212 rostralmiddlefrontal
3 -3.229 67407 163.06 -19.2 12.0
46.9 0.36360
0.35740 0.36980 337 superiorfrontal
4 -2.463 117667 37.51 -47.8 -50.8
8.0 0.63240
0.62620 0.63860 79 bankssts
5 -2.379 151243 12.92 -30.9 -42.8
36.6 0.63240
0.62620 0.63860 38 superiorparietal
I am trying to finish writing up my results and just
need answer to this
question to continue.
Thanks,
Judith S.
Mind Research Network
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Phone Number: 617-724-2358
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