Question about 3dLSS output (using stim_times_IM) - betas and T stats?


Quick question regarding the output of 3dLSS using single-trial betas via the stim_times_IM option in 3dDeconvolve. In general, the resultant dataset appears to have twice the number of subbricks as there are discrete stimulus time points. In other words, if my stim times file contains 12 time points, the dataset generated by 3dLSS has 24 subbricks. Unfortunately, the subbricks are not being written in a way that describes what exactly they are (all have a common #000 tag, but no other information).

I am assuming that, as with other AFNI datasets, this is because there are interleaved betas and t-stats. Is that correct?


EDIT: Solved. It appears that by using SPMG2 as my basis function, two beta estimates were output per stimulus instance. Switching to a BLOCK(9,1) (where 9 is the stimulus duration and 1 is the specified response amplitude) or SPMG1 function alleviates this issue. However, that does raise the question of whether BLOCK or SPMG1 is preferable here. If anyone has input on that, it would be much appreciated.