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Hello,

I would like to use a custom hemodynamic response function for the GLM.
Therefore I replaced the variable 'hrf' in the spm_hrf.m file with my function, sampled over 20 seconds and a resolution of 1 second which corresponds to my TR. See the last two lines in the attached file. I made no further changes.
However, when I specify a 1st-level model, the design matrix turns out to be just a uniform grey color.
My guess is that something about the amplitude or duration of my function is wrong, do you have any suggestions?
Could it be that the file spm_Gpdf.m needs to be changed as well, even though I think it should no longer be needed for my hrf.

Plan B, manually convoluting a boxcar function with this hrf in matlab and entering it as regressor in spm works perfectly but that is quite tedious.

Thank you very much.
Regards,
Felix

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Felix Schlegel
Institute for Biomedical Engineering :: University and ETH Zurich
HIT E22.1, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland
+41 44 633 69 38 :: [log in to unmask]<mailto:[log in to unmask]>