Thanks for clarifying Steve,
I guess that answers my last question as well. So, if I am understanding
this correctly, filtering out a component will remove all aspects of that
component. If part of that component intersected(temporal and spatially
matched) with EV's of interest, then strength of signal for the interested
EV's will decrease by a proportional amount. This proportional amount can
then be roughly estimated by looking at the % signal change and threshold
bar on the IC report page?
On Tue, 12 Feb 2008 07:43:51 +0000, Steve Smith <[log in to unmask]> wrote:
>Hi, MELODIC-based cleanup takes a component that you have selected,
>and 'multiplies' the component's timecourse by its spatial map, to
>produce a 4D dataset (of the same dimensions as your original data)
>that represents the artefact you selected. This is then simply
>subtracted out of the original data.
>
>Cheers, Steve.
>
>
>On 11 Feb 2008, at 19:05, Shawn Yeh wrote:
>
>> Dear FSL users,
>>
>> I am currently looking into using MELODIC to identify and filter out
>> excessive motion that cannot be adequately compensated by McFLIRT.
>> The FSL
>> website explains how to use Melodic, but I am having a hard time
>> finding out
>> how the filtering works. My questions:
>>
>> Does it average, smooth, or interpolate out the respective voxels with
>> respect to the component time courses(as generated by melodic), or
>> simply
>> reduce/increase the voxel intensity by the thresholded amount?
>>
>> In theory, doesn't including the motion estimates as separate ev's
>> already
>> attempt to 'devalue' these voxels associated with motion?
>>
>> Since the IC's usually have a periodic aspect to their model, how much
>> non-motion voxel changes are being filtered out? I understand
>> 'rimming'
>> effects are effectively removed this way, but I am looking at some
>> interleaving effects from motion that doesn't look as safe to filter
>> out.
>>
>>
>> Help on this topic greatly appreciated, thanks in advance,
>> Shawn
>>
>
>
>---------------------------------------------------------------------------
>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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