gPPI modeling conditions of no interest

Hello,

When running 3dDeconvolve for a gPPI analysis, should you include an interaction term for conditions of no interest?

For example, I am interested in how connectivity changes with a hippocampal ROI across four target conditions (hour, day, week, and month). In addition, I have modeled foil activation that is of no interest (stim_times 13) so that it is not included in the baseline. Do I still need the interaction term (stim_file 23)? Or should I leave it out and preserve a degree of freedom?

3dDeconvolve -input allruns_nobaseline+orig
-polort A
-num_stimts 23
-mask /usr/local/mridata/Consolidation_2019/atlases/Kirby/dil+orig
-stim_file 1 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_short.1D’[0]’ -stim_base 1 -stim_label 1 roll
-stim_file 2 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_short.1D’[1]’ -stim_base 2 -stim_label 2 pitch
-stim_file 3 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_short.1D’[2]’ -stim_base 3 -stim_label 3 yaw
-stim_file 4 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_short.1D’[3]’ -stim_base 4 -stim_label 4 dS
-stim_file 5 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_short.1D’[4]’ -stim_base 5 -stim_label 5 dL
-stim_file 6 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_short.1D’[5]’ -stim_base 6 -stim_label 6 dP
-stim_file 7 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_deriv_short.1D’[0]’ -stim_base 7 -stim_label 7 rolldx
-stim_file 8 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_deriv_short.1D’[1]’ -stim_base 8 -stim_label 8 pitchdx
-stim_file 9 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_deriv_short.1D’[2]’ -stim_base 9 -stim_label 9 yawdx
-stim_file 10 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_deriv_short.1D’[3]’ -stim_base 10 -stim_label 10 dSdx
-stim_file 11 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_deriv_short.1D’[4]’ -stim_base 11 -stim_label 11 dLdx
-stim_file 12 /usr/local/mridata/Consolidation_2019/${i}/${i}.results.secondhalf.noblur/motion_deriv_short.1D’[5]’ -stim_base 12 -stim_label 12 dPdx
-stim_times 13 …/timing_files/${i}‘_all_foils_tf_chop5.txt’ ‘TENT(0,14,8)’ -stim_label 13 all_foils
-stim_times 14 …/timing_files/${i}‘_hour_targets_tf_chop5.txt’ ‘TENT(0,14,8)’ -stim_label 14 hour_targets
-stim_times 15 …/timing_files/${i}‘_day_targets_tf_chop5.txt’ ‘TENT(0,14,8)’ -stim_label 15 day_targets
-stim_times 16 …/timing_files/${i}‘_week_targets_tf_chop5.txt’ ‘TENT(0,14,8)’ -stim_label 16 week_targets
-stim_times 17 …/timing_files/${i}‘_month_targets_tf_chop5.txt’ ‘TENT(0,14,8)’ -stim_label 17 month_targets
-stim_file 18 AllRuns_HIPP_Seed.1D -stim_label 18 Seed
-stim_file 19 AllRuns_Interaction_timeseries_hour.1D -stim_label 19 PPIHour
-stim_file 20 AllRuns_Interaction_timeseries_day.1D -stim_label 20 PPIDay
-stim_file 21 AllRuns_Interaction_timeseries_week.1D -stim_label 21 PPIWeek
-stim_file 22 AllRuns_Interaction_timeseries_month.1D -stim_label 22 PPIMonth
-stim_file 23 AllRuns_Interaction_timeseries_foils.1D -stim_label 23 PPIFoils
-jobs 16
-rout -tout
-bucket fxnConnOutput

Thank you,
Catherine

Hi Catherine,

These things are not always clear. If the stimuli for that extra condition are not tightly mixed with the others, it shouldn’t really matter. If they are, it might. But unless the degrees of freedom are a real problem (in which case there are bigger things to worry about), it should not hurt to include the extra regressor.

  • rick