gltsym option without redoing deconvolution


I am wondering if it is possible to use the gltsym option to calculate a contrast on the single subject level on an existing statistical BRIK output from a previous 3ddeconvolve operation. More specifically, I calculated single trial beta values using the stim_times_IM option, and I now want to calculate a linear trend across each subsequent trial of each condition. I know that I could redo this in a new 3ddeconvolve script with these gltsym options added, but this would require redoing all steps of the single trial beta calculation which is a bit time consuming over many participants. I also know I could code this in 3dcalc, but this option feels clunky compared to using the gltsym options. Any advice regarding 3ddeconvolve or performing this in 3dcalc is appreciated.

Adding GLTs to an existing result requires first running the program with -xsave, after which one can use -xrestore.

On the flip side, if you want to model the trend among the IM betas, that could be done by running a new regression on those betas.

  • rick

Thanks so much for the reply, I hadn’t noticed the xsave option before which is very useful.

For running new regression on betas, may that also be done using 3ddeconvolve? This is perhaps a silly question, but I am just wondering if there are any extra steps (extra option flags?) needed to run 3ddeconvolve on non-BOLD timeseries BRIK files. Or, may I simply input a statistical BRIK file, and specify how to weight each subbrik with “-stim_file”?

thanks again.