A few questions about the use of time and dispersion derivatives:
If one uses time and dispersion derivatives in a model, does this mean that
error variance associated with the canonical HRF is "soaked up" in the
model? If this is the case, then why wouldn't these be included as a matter
of routine when employing the standard HRF? I understand there are
waveforms that are devoid of some of the canonical HRF constraints, but
wouldn't using one of these mean that you are just incorporating into your
model what would otherwise be error variance in the canonical HRF situation?
Thanks,
Jeff
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