Hello Lila,
two relevant things beyond what Russel mentioned is that rotational
motion is much more difficult to correct for and thus more critical when
deciding to further analyze the data or not. The 2nd issue is whether
your motion peaks are correlated with your events or not. If so, motion
correction might strongly influence your signal.
Regards, Bartosz
> On Aug 2, 2005, at 7:54 AM, Lila Davachi wrote:
>
>> Hi all
>> I am looking for some guidance into how to decide if a subject has
>> simply moved "too much", in other words, how much motion is too much
>> motion?
>>
>> I have been using a shorthand guide and only have included Ss who
>> moved less then one voxel (in this case, 3mm) and trusted that
>> motion correction could handle that. But does the kind of motion
>> matter? For example, I have a subject now who only moved ~ 2mm across
>> a 1/2 hour scan but the motion was concentrated at specific times
>> with sharp peaks in the graph.
>>
>> So, my question is how can I convince myself that SPM has done a good
>> job at correcting the motion?
>> What are some tests of the data that I can implement (besides
>> including motion as a regressor..).???
>>
>> thanks much
>> lila
>>
>
> ---
> Russell A. Poldrack, Ph.d.
> Assistant Professor
> UCLA Department of Psychology
> Franz Hall, Box 951563
> Los Angeles, CA 90095-1563
>
> phone: 310-794-1224
> fax: 310-206-5895
> email: [log in to unmask]
> web: www.poldracklab.org
>
>
--
Dr. Bartosz Zurowski
Klinik für Psychiatrie und Psychotherapie
UKSH Campus Lübeck
&
Department of Systems Neuroscience
NeuroImage Nord, Bldg. S10, UKE
Martinistrasse 52 phone: 040-42803-3683
20246 Hamburg fax: 040-42803-9955
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