PowerPoint Presentation - Group Analysis with AFNI

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¥ STEP 3C: Calculate a voxel-by-voxel percent signal change with 3dcalc

GTake the 136 intensity values within each voxel, divide each one by the mean intensity value for that voxel (that we calculated in Step 3B), and multiply by 100 to get a percent signal change at each timepoint

GThis is where the A/B*100 equation comes into play

foreach run (1 2 3 4 5 6 7 8 9 10)

3dcalc-a ED_r{$run}_vr_bl+orig\

-b mean_r{$run}+orig \

-c full_mask+orig \

-expr Ò(a/b * 100) * cÓ \

-prefix scaled_r{$run}

end

åOutput of 3dcalc: 10 normalized datasets for Subject ED, where the signal intensity value at each timepoint has now been replaced with a percent signal change value

scaled_r1+orig, scaled_r2+orig É scaled_r10+orig