Hi all,
I want to duplicate the work in this paper (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.576.7913&rep=rep1&type=pdf). The HRF used in this paper is the standard HRF which is a synthetic function produced by combining two gamma functions (Friston et al., 1998; Handwerker et al., 2004) and is implemented in BrainVoyager QX.
I need to know the formula or parameters for this HRF. Because I want to duplicate the work using AFNI which has TWOGAM option in 3dDeconvolve (https://afni.nimh.nih.gov/pub/dist/doc/program_help/3dDeconvolve.html) with 5 parameters (time-to-peak and the full-width-at-half maximum of each gamma function, and the coefficient applied to the second one) need to input (https://afni.nimh.nih.gov/afni/community/board/read.php?1,157107,157123#msg-157123).
Perhaps the documentation of the hrf implemented in SPM might be useful: https://afni.nimh.nih.gov/afni/doc/source/spm__hrf_8m-source.html
It uses 7 parameters, though.
BrainVoyager uses the same parameters and default values as SPM.
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