The SPM HRF is a difference of gamma functions (one shifted in time wrt the other). I have not studied it a lot, but I have not seen much of a difference. The SPM HRF is a quasi-standard since most people in the world are using SPM, but that does not necessarily make it better:). The longer the stimulus, the less important it is, so it's less important for a block than for an event-related.

doug

Dan Dillon wrote:

Dear FreeSurfers,

What exactly is the difference between the HRF function in gammafit vs. SPMHRF? Are there reasons to prefer one to the other?

Thanks,

Dan Dillon, Ph.D.

Post-doctoral Fellow

Affective Neuroscience Lab

Dept. of Psychology, Harvard University

Phone: (617) 496-5222

E-mail: dillon@wjh.harvard.edu
_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer

-- 
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
Phone Number: 617-724-2358 
Fax: 617-726-7422

In order to help us help you, please follow the steps in:
surfer.nmr.mgh.harvard.edu/fswiki/BugReporting