SPMG3

AFNI Message Board
1

Hey AFNI experts,

I had a basic question regarding the SPMG3 option for 3dDeconvolve. I was wondering what the interpretation is for each of the 3 parameters (and their respective output sub-briks). I noticed in the 3dDeconvolve help, that SPMG2 is the gamma variate with the temporal derivative and the dispersion derivative. I don’t see it documented in the help what the added parameter for SPMG3 is.

Related, if you add a duration component to either of these options, does that output a separate parameter for the duration?

Thanks,

Danny

2

Danny,

Per the 3dDeconvolve help, there are two and three basis functions for SPMG2 and SPMG3, respectively.

if you add a duration component to either of these options, does that output a separate parameter for the duration?

Do you mean amplitude modulation through option ‘-stim_times_AM2’? If so, for each basis function you would have an associated modulation regressor.

3

Thanks Gang, I must have been looking at the wrong section where it explains each basis function.

Regarding the duration, 3dDeconvolve help shows you can add the stimulus duration to the modeling for SPMG. For example, if you have a 6-second stimulus, you could enter SPMG(6). I was wondering if the output has the duration modeled separately, but after looking at it, I see it doesn’t.

Thanks!

-Danny

4

3dDeconvolve help shows you can add the stimulus duration to the modeling for SPMG. For example,
if you have a 6-second stimulus, you could enter SPMG(6). I was wondering if the output has the
duration modeled separately, but after looking at it, I see it doesn’t.

So, for SPMG2/3 with -stim_times_AM2, how many beta values do you get in the output?

5

Hi Danny,

Duration is not modeled separately, it just affects
how long the basis function(s) are convolved for.
So the shapes of the regressors will be different.
The response to a longer event will have a longer
duration.

You will not get a separate beta for the duration,
if that is what you are asking.

  • rick