Blocks were separated by 20 s.

I attempted 3dsynthesize on one of my subjects. I added the cbucket option my 3dDeconvolve, with conditions modeled using the BLOCK function. I then ran:

3dSynthesize -cbucket ${results}/all_betas+orig \
-matrix ${results}/X.xmat.1D -select 12 -cenfill nbhr -prefix ${results}/PredictableNegative_timeseries.nii.gz

with the 12 in the -select option being the column for the Predictable Negative condition regressor.

Looking through the subbricks of the resulting file, I noticed that while the magnitude of the response was different for each voxel, the shape of the response was the same for all voxels, and seemed to be determined by the shape of the BLOCK function. That is, all the voxels in this time series had activation that ramped up over a a handful of TRs, stayed constant for the rest of the duration of the block, and then tapered back off over a handful of TRs. This made me think that this method won't give me what I want, which is the ability to look at the shape of the actual response during the block (but with noise and activity from other conditions regressed out). My guess is the using the fitts file has a similar issue - that the shape will be largely determined by the shape of the BLOCK function. This makes me think that rerunning 3ddeconvolve with the TENT function is what I want, since this will allow the data to take any shape, rather than having a particular shape imposed upon it.

Does my thinking here make sense, or am I missing something?