Hi
this assumes that the estimated motion correction parameters are the
correct representation of the motion. If you want to remove the 'full
model fit' only (which if I understand you correctly is simply a
linear combination of the 6 motion parameter vectors) then you can
simply add the same set of regressors to the feat model. Whether or
not this will improve things and wether or not it will be 'better'
than using standard melodic denoising will depend on the nature of the
motion - all bets are off. Using the full denoising approach (even in
the case where there is partial correlation with the design) is
conservative in the sense that it should never increase the chance of
false positive detection - as you say the worst that can happen is
that you'll throw the baby out with the bathwater..
hth
christian
On 26 Mar 2008, at 19:41, Kent Conover wrote:
> Hi Dr. Beckmann and other FSLers,
>
> I often find that a MELODIC time course component is a mixture of
> motion
> effects and a design component. This is made abundantly clear when I
> include
> the motion correction parameter vectors as explanatory variables in
> the
> MELODIC analysis! Nevertheless, the "IC time course" is often
> systematically
> different from the "full model fit" time course. To avoid throwing
> the baby
> out with the bath water I would prefer to remove only the full model
> fit. So
> I have three questions. Is this advisable? If so, can MELODIC
> presently do
> it? If not, would a file that is composed of the full model fit
> vectors, but
> is otherwise similar to the "melodic_Tmodes" files do the trick?
>
> Regards,
>
> Kent Conover
_______________________________________________
Christian F. Beckmann, DPhil
Senior Lecturer, Clinical Neuroscience Department
Division of Neuroscience and Mental Health
Imperial College London
Hammersmith Hospital - London W12 0NN
Tel.: +44 (0) 208 383 3722 --- Fax: +44 (0) 208 383 2029
Email: [log in to unmask]
http://www.imperial.ac.uk/medicine/people/c.beckmann/
Senior Research Fellow, FMRIB Centre
University of Oxford
JR Hospital - Oxford OX3 9DU
Tel.: +44 (0) 1865 222552 --- Fax: +44 (0) 1865 222717
Email: [log in to unmask]
http://www.fmrib.ox.ac.uk/~beckmann
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