Hi all,

I had a question regarding the interpretation of the beta weights produced by 3dDeconvolve. For my experiment, I have analyzed each subject's breathhold data in 3dDeconvolve using the following script:

3dDeconvolve -input 101.breathhold.BOLD.nophymotcorr.tcat.scale.nii \
-polort 2 \
-num_stimts 1 \
-stim_times 1 breathhold_stimulus.1D 'BLOCK(15,1)' \
-stim_label 1 breathhold \
-iresp 1 BH_test.101 \
-jobs 2 \
-fout -tout -rout -bout -x1D X_test.xmat.1D -xjpeg X_test.jpg \
-fitts fitts_test.101 \
-errts errts_test.101 \
-bucket stats_test.101

For the stim_times I have a breathhold_stimulus.1D file that has the breathhold onset times, plus a delay that represents the average amount of time it took for the BOLD signal to peak after each breathhold for that subject. For example, a participant might have a BOLD signal that peaks 8.7 seconds on average after each breathhold. Their stimulus times file would read 43.7 90.7 137.7 184.7 231.7.

Now I am extracting mean values from the breathhold coefficient subbrick of the resulting stats file from different ROIs using 3dROIstats. What does this number represent? If I understand correctly, 3dDeconvolve runs a GLM on each voxel and estimates the beta weight. I also understand that a beta weight is the average amount by which the dependent variable increases when the independent variable increases one standard deviation and other independent variables are held constant. But what does this mean in this context? What unit is this amount measured in? Your thoughts are much appreciated!

Best,
Alain



Edited 1 time(s). Last edit at 07/04/2016 12:08AM by Alain.