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
Greig de Zubicaray wrote:
>
> I posted a question a couple of weeks ago re the use of a fourier set in a
> sparse design er-fMRI experiment, but didn't receive a reply.
>
> I have two conditions/event types (control and task) delivered in randomised
> order that I have modelled with non-windowed fourier sets without HRFs, and
> have also entered the realignment parameters for each subject as covariates
> in the design matrix. Although I have the resulting F-contrasts for each
> condition, I would now like to compare them in a manner analogous to a
> subtraction design. I understand that this is not straightforward given that
> I have used fourier sets.
>
> I can think of possibly two ways of doing this in SPM99 involving exclusive
> masking or orthogonalising the contrasts to see if the task condition
> accounts for more variability than the control condition, but am not
> entirely sure how to proceed or how best to interpret the results of these
> approaches. Could anyone provide me with some information as to the relative
> merits of each approach and how best to interpret the results?
>
> thanks,
>
> Greig
>
> --
> Centre for Magnetic Resonance
> The University of Queensland
> Brisbane, QLD 4072
> AUSTRALIA
>
> Tel: +61 (0) 7 3365 4250
> Fax: +61 (0) 7 3365 3833
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