Dear Donald,
thanks, I have just realized it by looking in to spm_detrend function code.
Thank you.
Stefan
MCLAREN, Donald wrote:
> Stefan,
>
> The process is demeaned (not detrended). This is part of normal
> regression and doesn't influence the results. However, you will want to
> convolve this with the HRF before hand.
>
> Best Regards, Donald McLaren
> =================
> D.G. McLaren, Ph.D.
> Postdoctoral Research Fellow, GRECC, Bedford VA
> Research Fellow, Department of Neurology, Massachusetts General Hospital
> and Harvard Medical School
> Office: (773) 406-2464
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> 2011/3/23 Štefan Holiga <[log in to unmask] <mailto:[log in to unmask]>>
>
> Dear experts,
>
> I am analysing a simple finger tapping block design experiment and I
> am trying to add additional regressor to my stimulus signal, a
> signal recorded and computed using sensory glove capturing the
> actual finger tappping movement. This signal is somehow reflecting
> the movement performance (both amplitude and temporal
> characteristics of movement) of patients during the experiment.
>
> My problem is, that SPM is detrending all the regressors in the
> design matrix. I assume it is not what I want (see the picture
> attached). The black line shows what I would like to have there, the
> green one after SPM's detrending.
>
> My questions are, is there any way of circumventing this without
> making changes in code? Or is the detrending of my regressor necessary?
>
> Thank you very much in advance and I wish you a fruitful day.
>
> Stefan
>
>
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