> Thanks for this. Unfortunately, this solution didn't work. When I tried to
> test the sum of pairwise differences between components as suggested below,
> the contrast manager accepted the specification but then crashed out with
> the error message "matrix dimensions must agree" when I clicked OK. I tried
> it again after running the analysis without the realignment parameters as
> covariates, and got the same error message. However, this seemed to work:
>
> exp con
>
> 1 0 0 ... -1 0 0 ...
> 0 0 1 ... 0 0 -1 ...
I don't know why this is. Perhaps you could send me exactly what you
typed
as the contrast? It might help if you also email me a graphic of your
design
matrix (we should do this in private, and announce the results to the
list,
to reduce the amount of traffic these days!).
> Also, I assume that if I did get the result I wanted from this comparison I
> would have to plot the fitted responses to see what direction the
> differences were in?
Yes.
> FYI, I modelled the responses using only the first
> order fourier component with the window length set to the image acquisition
> time.
Do you mean the TA/TR, or the whole session acquisition time? Either
way,
the window length doesn't make much sense...
> thanks,
>
> Greig
>
> > From: Rik Henson <[log in to unmask]>
> > Reply-To: Rik Henson <[log in to unmask]>
> > Date: Thu, 05 Oct 2000 08:46:07 +0100
> > To: Greig de Zubicaray <[log in to unmask]>
> > Cc: "[log in to unmask]" <[log in to unmask]>
> > Subject: Re: fourier sets and F-contrasts
> >
> >
> > Greig
> >
> > Simply construct an F-contrast comparing each Fourier component
> > separately, eg:
> >
> > exp con
> >
> > 1 0 0 ... -1 0 0 ...
> > 0 1 0 ... 0 -1 0 ...
> > 0 0 1 ... 0 0 -1 ...
> >
> > or more simply, with N Fourier components, type:
> >
> > eye(N) -eye(N)
> >
> >
> > Rik
> >
> >
> >
> > --
> > ---------------------------8-{)}-------------------------
> >
> > DR R HENSON
> > Institute of Cognitive Neuroscience &
> > Wellcome Department of Cognitive Neurology
> > 17 Queen Square
> > London, WC1N 3AR
> > England
> >
> > EMAIL: [log in to unmask]
> > URL: http://www.psychol.ucl.ac.uk/rik.henson/index.html
> > TEL1 +44 (0)20 7679 1131
> > TEL2 +44 (0)20 7833 7472
> > FAX +44 (0)20 7813 1420
> >
> > ---------------------------------------------------------
> > --
--
---------------------------8-{)}-------------------------
DR R HENSON
Institute of Cognitive Neuroscience &
Wellcome Department of Cognitive Neurology
17 Queen Square
London, WC1N 3AR
England
EMAIL: [log in to unmask]
URL: http://www.psychol.ucl.ac.uk/rik.henson/index.html
TEL1 +44 (0)20 7679 1131
TEL2 +44 (0)20 7833 7472
FAX +44 (0)20 7813 1420
---------------------------------------------------------
--
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|