Hello,
As an extension of this reasoning is it therefore legitimate to
perform ANOVA on the four beta images from each subject of Dr Mathalon's
study?
thanks,
Jason.
On Mon, 2 Dec 2002, Will Penny wrote:
>
> Daniel H. Mathalon wrote:
>
> > Dear SPMers,
> >
> > We have modeled 4 trial types
> (A,B,C,D) in an event-related design in two
> > groups of subjects. In addition to
> examining condition contrasts (e.g.,
> > B-A, A-B) within and between the
> groups, we are interested in knowing how
> > the groups differ specifically in
> response to condition A. Therefore, we
> > would like to perform a two group
> t-test on the beta image associated with
> > A.
> >
> > It is generally understood that fMRI
> analysis requires contrasts between
> > conditions, which would seem to
> suggest that we cannot validly compare
> > groups on a single condition. Yet,
> to the extent that the beta image
> > reflects the peak of the fitted HRF,
> it seems natural to ask whether this
> > peak is larger in one group versus
> another.
> >
> > Can anyone clarify whether we can
> legitimately compare a beta image (rather
> > than a CON image) between groups, and
> if not, why not?
> >
>
>
> This is perfectly legitimate. In fact
> the contrast vector [1 0 0 0] will
> produce a CON image that is identical to
> the beta image for trial type A. Two
> group t-tests can then be implemented on
> the resulting CON/BETA images.
>
> Best wishes,
>
> Will.
>
>
> > Thanks.
> > Daniel H. Mathalon, Ph.D., M.D.
> > Assistant Professor
> > Department of Psychiatry
> > Yale University School of Medicine
> >
> > Psychiatry Service 116A
> > VA Connecticut Healthcare System
> > 950 Campbell Avenue
> > West Haven, CT 06516
> >
> > Phone (203) 932-5711, ext. 5539
> > FAX : (203) 937-3886
> > Pager : (203) 867-7756
> > e-mail: [log in to unmask]
> >
> >
> >
>
>
> --
> William D. Penny
> Wellcome Department of Imaging Neuroscience
> University College London
> 12 Queen Square
> London WC1N 3BG
>
> Tel: 020 7833 7478
> FAX: 020 7813 1420
> Email: [log in to unmask]
> URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
>
>
>
> --
> William D. Penny
> Wellcome Department of Imaging Neuroscience
> University College London
> 12 Queen Square
> London WC1N 3BG
>
> Tel: 020 7833 7478
> FAX: 020 7813 1420
> Email: [log in to unmask]
> URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
>
Jason Steffener, RTS V
Department of Psychiatry
New Jersey Medical School
Newark, NJ USA
(973) 972-1604
http://www.umdnj.edu/~steffejr
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