Hi Estephan,
The dvars calc in fsl_motion_outliers is scaled in a manner to match the
definition in Power's 2012 paper. So a dvars cutoff of 5 in that paper
would be 5 in fsl_motion_outliers as well. Note that the pre-processing
applied can have a big impact on the dvars values, and the pre-processing
applied in Power 2012 included spatial smoothing, band-pass filtering, and
multiple regression of various nuisance regressors, all of which will
drive down the dvars values relative to data that is solely motion
corrected.
cheers,
-MH
--
Michael Harms, Ph.D.
-----------------------------------------------------------
Conte Center for the Neuroscience of Mental Disorders
Washington University School of Medicine
Department of Psychiatry, Box 8134
660 South Euclid Ave. Tel: 314-747-6173
St. Louis, MO 63110 Email: [log in to unmask]
On 11/19/12 10:57 AM, "Estephan Moana" <[log in to unmask]> wrote:
>Thanks for the wiki doc, Mark. It is very helpful in understanding the
>script function.
>
>I was looking the code for fsl_motion_outliers after reading the Power et
>al (2012) paper, and one question remains. What are the units for the
>"refrms" and "dvars" metrics? Power et al showed "dvars" as "delta % BOLD
>x 10", and after looking the output in my files it seems that
>fsl_motion_outliers outputs "delta % BOLD x 100". Is that correct? If so,
>in order to replicate their cutoff for "dvars" of 0.5% delta BOLD I
>should use the threshold option as "--thresh=50"?
>
>Estephan
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