AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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defenderfer
August 19, 2019 10:30AM
Their suggestion:

T-stat cluster statistic
The spatial (brain-space) covariance of the image based on the regularized Guass-Markov equation would be
CovBeta = inv(X'*X+lambda*I) * R
Where R is the channel-channel covariance and X is the forward model.
If your ROI/cluster is given by the contrast vector c = [0 0 0 1 1 1 1…] where the length of c is the number of voxels and is 1 in the cluster and 0 else, then the T-test is
T = c * Beta / sqrt(c* CovBeta * c')
This would be the T-test over the cluster accounting for the fact that neighboring voxels in the reconstruction are not independent.
The F-test version would be something more like
VarianceExplained by cluster = sum ( X * c * Beta )^2 /(k-1)
Variance of residual = sum ( Y - X*c*beta) ^2 ) / (n-k)
F = SSM/SSR
I think n in this case the number of channels and k is 2 (?) [the number of clusters + the DC term) . But, check this.

I don't know how to implement this in my data. I'm still reading/learning about the options in 3dclustsim, so there may be a way to address these things. Any advice is appreciated!
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Subject Author Posted

fNIRS image reconstruction method using AFNI tools

defenderfer August 14, 2019 02:03PM

Re: fNIRS image reconstruction method using AFNI tools

discoraj August 16, 2019 10:49AM

Re: fNIRS image reconstruction method using AFNI tools

defenderfer August 19, 2019 10:30AM

Re: fNIRS image reconstruction method using AFNI tools

discoraj August 30, 2019 12:09PM

Re: fNIRS image reconstruction method using AFNI tools

defenderfer September 03, 2019 12:37PM