Basically, it's a scan where each subject views stimulus A (say for 5
seconds) followed by crosshairs (say for 10 seconds) and stimulus B
followed by crosshairs, repeated several times during a scan.
-Brad
----- Original Message -----
From: "Stephen Smith" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, September 10, 2005 7:19 AM
Subject: Re: [FSL] settle an argument
> Hi Brad, I'm afraid I can't work out what you mean by "group of subjects
> scanned under condition A and B is a randomized design within a scan" -
> what exactly is going on at first level?
>
> Cheers, Steve.
>
>
> On Fri, 9 Sep 2005, Brad Goodyear wrote:
>
> > Hi
> >
> > I was hoping that someone could settle an argument I am having with a
> > colleague.
> > Suppose I have a group of subjects scanned under condition A and B is a
> > randomized design within a scan.
> >
> > I claim that it is best to generate COPEs for A and B separately for
> > each individual at the first level, and then generate the A minus B
> > contrast at the second level across the group.
> > He claims it is best to generate the A minus B contrast for each
> > individual at the first level, and then generate the group contrast at
> > the second level.
> >
> > Which way is better?
> >
> > -BRad
> >
>
> --
> Stephen M. Smith DPhil
> 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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