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 mailto:dillon@wjh.harvard.edu
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