Hi Patricia,
You're right -- the best way is to use some sort of basis function set that
allows flexibility in the timing and shape of the HRF. In the simplest
form, the canonical HRF + its temporal and spatial derivatives is one such
set. Another method would be to use the FLOBS option in Feat, which will
provide a more general basis set that you can customize. In any event,
you'll need to use something like tsplot to reconstruct the basis set into
an estimated HRF using peri-stimulus time plotting at your voxel(s) of
interest.
Hope this helps.
Joe
|