Hi - sorry, I thought you were talking about the general pre-
processing steps. To turn off the use of neighbours in the whitening
just follow my second answer from the last email - cheers.
On 20 Mar 2006, at 15:57, Lu Yuefeng wrote:
> Hi Steve,
>
> Thanks for your answers! I have one more question. Could
> you specify the commands and options to prevent using spatial
> information to do noise var/cov estimation, since what I really
> wanted is to simulate a few hundred time series and compare their
> estimates with other software.
>
> Thanks a lot!
>
> Yuefeng
>
>
>
> On 3/20/06, Steve Smith <[log in to unmask]> wrote: Hi,
>
> On 19 Mar 2006, at 21:57, Lu Yuefeng wrote:
>
> > Hi Steve,
> >
> > Thanks a lot for your advice! I got two questions
> >
> > (1) I was wondering when I analyze the simulated brain, whether I
> > could turn off some options to prevent using spatial information
> > to estimate noise/covariance.
>
> Indeed, that's right.
>
> > (2) If you would clarify the following question, that would be very
> > helpful for my understanding of SUSAN algorithm. When the same time
> > series were put into a big enough clsuter, would the noise variance/
> > covariance estimates for the time series on the center voxel be the
> > same as those estimates from a single time series, when SUSAN
> > algorithm is used?
>
> If you set the mean intensity of the voxel of interest such that it's
> very different from the mean of its neighbouring voxels, then SUSAN
> will not include those voxels in the whitening estimation.
>
> Good luck - cheers, Steve.
>
>
> >
> > TIA!
> >
> > Yuefeng
> >
> >
> >
>
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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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