Dear Clara,
Orthogonalising with respect to the unmodulated regressor corresponds to
mean-centring, so, in your case, you could enter mean-centred parametric
modulators with "orthogonalise modulations" set to "no".
Best regards,
Guillaume.
On 22/05/2021 00:34, Clara Sanches wrote:
> Hello,
>
> I am reviving this discussion on how to set parametric regressors in SPM12 since I am also trying to find how to orthogonalize two parametric regressors only with respect to the unmodulated regressor without orthogonalizing them with respect to each other (SPM8 orthogonalizes each regressor with respect to the ones preceding it, I’m not sure if this is the case for SPM12 but from what I’ve been reading it is, please correct me if I'm wrong).
>
> So, from the answers here, there is no way of doing this in SPM12? I would have to set orthogonalization to ‘no’ and enter my regressors modified? Or define two separate models with the order of the parametric regressors changed.
>
> Since this thread is from 2019 I was wondering if someone has a found way (maybe through code changing) of orthogonalizing parametric regressors with respect to the unmodulated regressor only?
>
> Any suggestion is much appreciated!
>
> Thank you,
> Clara
>
--
Guillaume Flandin, PhD
Wellcome Centre for Human Neuroimaging
UCL Queen Square Institute of Neurology
London WC1N 3BG
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