help > Why denoised rfMRI data have normal density
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Sep 7, 2019  09:09 AM | Alireza Talesh Jafadideh - Tarbiat Modares University
Why denoised rfMRI data have normal density

After performing essential preprocessing steps (slice timing, realignment, co-registration, segmentation, normalization, and smoothing) in SPM12, I loaded the normalized T1 image and also normalized (not smoothed) Functional images into CONN toolbox. Then, I defined the motion parameters (extracted by SPM12) in 1st level covariates. In the option settings, I selected only voxel-voxel analysis and "create confound-corrected time series". Finally, I press "Done" button to go for "Denoising" step. In the "Denoising" step, I considered the "White Matter (5P)", "CSF (5P)", and "Motion Parameters" as confounds. The band-pass filter was [0.01, 0.1]Hz and linear detrending was selected.
I have provided the density plot of my normalized rfMRI (loaded as functional images in CONN toolbox) and also density plot of its denoised version in CONN toolbox. They have completely different density and the denoised version shows a normal density. I know the connectivity density is normal (as shown in CONN toolbox) but I don't know why my denoised rfMRI time series show normal density?
In another try, I loaded my rfMRI data in CONN toolbox and carried out "Setup" step as described above. However, in "Denoising" step, I didn't select any confounds, any despiking, any detrending and band-pass filter [0.0001,200]Hz was applied. I expected to achieve rfMRI data showing density the same as or at least similar to my normalized rfMRI data. However, interestingly, the achieved rfMRI data again had normal density. I really don't know why? And what the CONN toolbox does when I have not selected any option for denoising?
I really am worried about my processed results and I don't know that can I trust on my denoised results?
I have considered "niftiDATA_Subject001_Condition000.nii' as denoised data.

Any response would be appreciated.


Attachment: Images.pdf