HC
You might want to try some noise reduction techniques - including
motion parameters in the model, improving registrations, ICA denoising
etc.
Cheers,
Eugene
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Centre for Functional MRI of the Brain (FMRIB) | University of Oxford
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On 18 November 2010 07:48, Stephen Smith <[log in to unmask]> wrote:
> HI - this is indeed the generally recommended approach - however, IF the
> trend is truly linear then you will get a slightly more sensitive analysis
> having only one EV (or one for mean and one for slope). Your residuals will
> go up (unless things are perfectly linear), but so will your degrees of
> freedom. I'd be surprised though if this makes things better.
> Cheers
>
>
> On 17 Nov 2010, at 21:04, HC wrote:
>
> Hello experts!
>
> I have a design in which I have 4 levels of a treatment: 1, 2, 3, and 4. I
> predict that signal should be a monotonically increasing function with 1
> having the lowest signal and 4 having the greatest. What is the best way to
> set up my EV files to test this?
>
> In the past, I have tried 1 EV per treatment level, and then used a contrast
> of :
>
> level 1 level 2 level 3 level 4
> -3 -1 1 3
>
> But this method seems to not be quite sensitive enough to detect the effect.
> Any other suggestions?
>
> Thank you in advance for your help!
>
>
>
> ---------------------------------------------------------------------------
> Stephen M. Smith, Professor of Biomedical Engineering
> Associate Director, Oxford University FMRIB Centre
>
> FMRIB, JR 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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