Hi, yes, the rank deficiency of this design is a problem in _any_
GLM-based analysis; you need to exclude one of the conditions (effectively
treating it as "rest"), i.e., just drop the final EV.
Note that this is more normally stimulated and modelled using sinusoids -
would that be appropriate for your data/design?
Regards, Steve.
On Wed, 26 Feb 2003, Beth Krauss wrote:
> Hello, I am presenting a visual stimulus consisting of annuli that give
> the impression of radiation out wards; in reality it is a series of 10
> concentric annuluses shown one after the other (the classic retinotopic
> radiating checkerboard annulus). Once the largest annulus size is
> reached it starts at the smallest size and continues on. There are no
> "rest" cycles. When I try to run the FSL analysis I get the error
> message …at least 1 EV is a linear combination….. Which is true, my 10
> EVs corresponding to the 10 annuluses, do combine to form a linear
> combination. Can I analyze my data in FSL? Thanks! Beth
>
Stephen M. Smith MA DPhil CEng MIEE
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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