I think that for something as simple as ankle dorsiflexion, if the
results are in a plausible location, you can believe them. The motion
really isn't that bad. It's hard to keep a patient still when doing foot
movements, so there will probably always be stimulus-correlated motion,
and if you include the motion parameters as regressors (as you have seen
already), it'll get rid of any true activation.
Gandolla Marta wrote:
> Hi Chris and everyone else!!
>
> indeed, we are looking at right ankle dorsiflexion and yes, I
> definitively agree that the activation seems to be quite posterior.
> the graph I posted has on x axis the number of scan (TR=3secs, 5
> minutes of acquisition). on the y axis there are mm for blue, green
> and d line, and degrees for yellow, cyan and magenta line. I
> superimposed all the realignemnt parameters along with the block
> design to search for the eventual correlation. I attached in any case
> te SPM output of realignment.
>
> all my best
> marta
> 2010/8/26 Chris Watson <[log in to unmask]
> <mailto:[log in to unmask]>>
>
> Is it right ankle dorsiflexion that you're looking at?
> It looks pretty posterior to the motor strip; what does it look
> like overlaid on a structural?
> What's the scale (units) of the graph you posted? Can you post the
> output of SPM's realignment?
>
>
> Gandolla Marta wrote:
>
> Hi everyone,
> I attached a pdf file instead of a docx of the previous
> e-mail. sorry for the inconvenience!!
> I'd need some help about realignment parameters effect that
> seems to be huge in the acquisition I will now describe.
> We have a 30 secs block design, starting from rest. The
> patient is performing active ankle dorsiflexion during on blocks.
> We did the following preprocessing steps:
> - realignment
> - coreg
> - normalize
> - smooth (6mm)
> then we implemented the GLM with a 8 columns design matrix
> (1-condition with the 30 secs block design, 2-7- realign
> param, 8- baseline) and we found zero activation (p<0.01 FWE
> corrected).
> we then chacked with the 2 columns design matrix (1-condition
> with the 30 secs block design, 2- baseline) and we found a
> quite important activation (fig.1). should we trust this
> activation? the realignemnt param plot along with the block
> design protocol is shown in fig.2. is it possible that all
> this effect depends on the correlation between the realignment
> parameters and the condition column in the design matrix?
> should trust only the design with the realignement parameters
> as covariats of no interest? we are thinking in this case why
> we don't see any activation... do we miss something?
> thanks for your help
> best regards
> marta
>
>
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