Hi,
I don't think you're allowed to call anything in the _model_ an
'artifact' ;-)
I'm not sure what you're wanting the model to look like - do you want
it to be very long or very short? Have you tried playing with the
convolution options?
Cheers.
On 1 Oct 2007, at 17:10, Kent Conover wrote:
> Hi,
>
> I have a question that appears related a query about “strange dips”
> in the August 1st 2007 FSL
> digest. In my design subject ratings are used as a Custom 1
> predictor. The subjects are presented
> with a long duration thermal stimulus (270 second cycle).
> Subsequently, the subject rating is often
> constant at the beginning of each scan. Unfortunately, a initial
> “spike” artifact appears in the ev
> after it is convolved with an HRF. While I can make this problem
> "go away" by not convolving with
> the HRF, I would like to know if there anything else that I can do.
>
> Regards,
>
> Kent Conover,
> Research Associate,
> Centre for Studies in Behavioral Neuribiology,
> Concordia University,
> Montreal, Canada
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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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