Hi hcp-users, I'm new to resting state connectivity analysis (and this list-serve), and I have a few basic questions about applying it to the HCP data. I'm using the minimally preprocessed REST1 data.
1. The low-pass filtering seems "controversial", though commonly employed -- is there at this point an agreed-upon way to remove deleterious high frequency noise? In addition, I'm having difficulty with temporally filtering the data in fsl. To bandpass data from .009 - .08 Hz, I'm running: fslmaths nii_in -bptf 77.16 8.68 nii_out where 77.16 = sigma_hipass = 1/(2 * TR * F_hicutoff), for TR = .72 and F_cutoff = .009 and 8.68 = sigma_lopass = 1/(2 * TR * F_locutoff), for TR = .72 and F_locutoff = .08 This *seems* correct (I at least confirmed with the feat gui that the conversion from cycle time to sigma is 1/(2*TR)). However, when I look at the data in the frequency domain, it looks like there is significant response left for frequencies below .009 Hz (picture attached) and very little between .01-.08. Does anyone know if I'm doing something incorrectly, or if the frequency cutoff for a Gaussian filter is just very gradual? 2. Any additional preprocessing is recommended, besides temporal filter and what the minimal pre-processing has already enacted? 3. What is an intelligent way to combine correlation matrices? Averaging (Power et al, 2011)? Binarizing the correlation matrix by setting the top 10% of voxels to 1 and the rest to 0, and averaging the binarized matrices (Yeo et al, 2011)? Either? Something fancier? Any advice or additional resources would be enormously appreciated -- thanks very much!! Kim -- Kimberly Stachenfeld, BS Graduate Student 236A Princeton Neuroscience Institute Washington Road Princeton, NJ 08544 [email protected] _______________________________________________ HCP-Users mailing list [email protected] http://lists.humanconnectome.org/mailman/listinfo/hcp-users
freqResponse_tempFiltering.pdf
Description: Adobe PDF document
freqResponse_tempFiltering_zoom.pdf
Description: Adobe PDF document
