Hi,
I don’t know where to ask this question to report uncorrected maps and I hope some experts here could help me....
I have 10 subjects in my experiment. The fmri image of each subject is 64x64x35 with 3.75x3.75x4 mm voxel size. In my 1st-level analysis, images were coregistered to the corresponding T1-weighted image (image 256x256x192; voxel size 0.98 x 0.98 x 1 mm) and then normalized to the standard MNI template. The resulting resampled voxel volume of the normalized images was 2 x 2 x 2 mm. Data were then smoothed using an 8-mm FWHM. First-level t-contrasts were then entered into a second-level 1-sample t-test to produce an average group activation map. Results showed that no voxels survived corrected threshold, but I’d like to make the correction at the cluster level by 3dClustSim in AFNI.
<Q1>
To determine the minimal cluster size with a cluster threshold of 0.05, I tried individual voxel p = 0.005 using the command below:
3dClustSim -nxyz 64 64 35 -dxyz 3.75 3.75 4 -fwhm 8 -iter 10000 -pthr 0.005 –athr 0.05
Am I correct?
<Q2>
Actually we also did voxel-based morphometry analysis and thus I made an average gray matter mask (gm) of all subjects. I wanted to confine the analysis in gray matter voxels only, not the whole brain. I then did:
3dClustSim -mask gm –iter 10000 -pthr 0.005 –athr 0.05
Is this correct? (I think maybe not because their image and voxel dimensions are different from fmri but I need your comments).
I do appreciate any help.
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