It could be fundamentally different or it could just be in the
analysis. Categorical data has no assumption about the relationship
between values or conditions; whereas parametric designs assume a
relationship. However, parametric designs can also be modelled like
categorical data, but not vice versa. When I've done a parametric
design, I've treated it like categorical data so that I don't have to
assume any apriori relationship and can define the relationship from
the data. If you model something parametrically, there is one column
Most people just look at the canonical HRF term. If you want to
incorporate the derivative terms, I'd read the earlier posts from this
week or last week by Jason Steffener.
Best Regards, Donald McLaren
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General
Hospital and Harvard Medical School
Office: (773) 406-2464
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On Fri, Feb 18, 2011 at 12:26 PM, Javier Navas <[log in to unmask]> wrote:
> Hi SPMers!
> I have some doubts in the analyses of fMRI data:
> What is the difference between the Parametric or categorical design?? and,
> regarding the contrast specification?
> And, in case you use temporal derivatives of the canonical HRF how should
> I´ll be the contrast for a single task?
> thank you all!!
> Francisco Javier Navas Sánchez
> Laboratorio de Imagen Médica U.M.C.E.
> Hospital General Universitario Gregorio Marañón
> Dr Esquerdo 46, 28007 Madrid, Spain
> Phone : (+34) 91 426 50 67 Fax: (+34) 91 426 5108
> e-mail:[log in to unmask] http://image.hggm.es