Regression - bandpass & polort

Hi all,

I am processing a set of resting state images using AFNI version 21.2.04 (‘Nerva’). I am currently running a few versions of manipulating the nuisance regressors (e.g., motion censoring, outlier censoring, bandpass filtering) to determine a final model to move forward with. I noticed that the polort value is consistently set to 4 across models, regardless of whether bandpass filtering is performed. In the 3dTproject documentation, I saw that it is not recommended to use a value greater than 2 when bandpassing out lower frequencies.

Is it OK to use a polort value of 4 while bandpassing (0.01-0.1 Hz)? Or would you recommend lowering this value in the models where bandpassing is included (e.g., -regess_polort 2 -regress_bandpass 0.01 0.1)?

Thank you,
Jenna                                                                                                            \
                 -subj_id ${sid} -script proc.${sid} -scr_overwrite -out_dir ${sid}.results                             \
                 -blocks despike tshift align tlrc volreg blur mask scale                                               \
                     regress                                                                                            \
                 -radial_correlate_blocks tcat volreg                                                                   \
                 -copy_anat ${ss_dir}/anatSS.${sid}.nii                                                                 \
                 -anat_has_skull no                                                                                     \
                 -anat_follower anat_w_skull anat  ${ss_dir}/anatU.${sid}.nii                                           \
                 -anat_follower_ROI aaseg anat ${fs_dir}/aparc.a2009s+aseg.nii.gz                                       \
                 -anat_follower_ROI aeseg epi ${fs_dir}/aparc.a2009s+aseg.nii.gz                                        \
                 -anat_follower_ROI FSvent epi ${fs_dir}/fs_ap_latvent.nii.gz                                           \
                 -anat_follower_ROI FSWe epi ${fs_dir}/fs_ap_wm.nii.gz                                                  \
                 -anat_follower_erode FSvent FSWe                                                                       \
                 -dsets ${raw_epi}                                                                                      \
                 -tcat_remove_first_trs 4                                                                               \
                 -tshift_opts_ts -tpattern ${tpattern}                                                                      \
                 -align_opts_aea -cost lpc+ZZ -giant_move -check_flip                                                   \
                 -tlrc_base MNI152_2009_template_SSW.nii.gz                                                             \
                 -tlrc_NL_warp                                                                                          \
                 -tlrc_NL_warped_dsets ${ss_dir}/anatQQ.${sid}.nii ${ss_dir}/anatQQ.${sid}.aff12.1D                     \
                     ${ss_dir}/anatQQ.${sid}_WARP.nii                                                                   \
                 -volreg_align_to MIN_OUTLIER                                                                           \
                 -volreg_align_e2a                                                                                      \
                 -volreg_tlrc_warp                                                                                      \
                 -blur_size 4                                                                                           \
                 -mask_epi_anat yes                                                                                     \
                 -regress_motion_per_run                                                                                \
                 -regress_ROI_PC FSvent 3                                                                               \
                 -regress_ROI_PC_per_run FSvent                                                                         \
                 -regress_make_corr_vols aeseg FSvent                                                                   \
                 -regress_anaticor_fast                                                                                 \
                 -regress_anaticor_label FSWe                                                                           \
                 -regress_censor_motion 0.3										\
 	      	 -regress_censor_outliers 0.1										\
		 -regress_bandpass 0.01 0.1                                                                             \
                 -regress_apply_mot_types demean deriv                                                                  \
                 -regress_est_blur_epits                                                                                \
                 -regress_est_blur_errts                                                                                \
                 -html_review_style pythonic 

Hi Jenna,

Go ahead and use -polort 2 when doing that bandpass filtering. It is okay to include -polort 4, but it is a mostly unnecessary loss of 2 more degrees of freedom.

  • rick