[Mne_analysis] SSP projection and the forward gain matrix
alexandre.gramfort at telecom-paristech.fr
Tue Jul 1 10:42:28 EDT 2014
> The noise is decomposed to
> bn(t) = U * cn(t) + e(t),
> where e(t) is white noise.
> Let y(t) be the sensor signal and x(t) be the source signal
> y(t) = G x(t) + bn(t)
> so if we apply the SSP operator (I - UU'),
> (I-UU') y(t) = (I-UU')G x(t) + (I-UU') bn(t)
> = (I-UU')G x(t) + (I-UU') e(t)
this is correct.
> So I thought when applying the SSP to the sensor data, the forward matrix
> should also be multiplied by the operator.
> But when I tried to read through the python code in
> "mne.minimum_norm.inverse", I did not find this kind of operation.
> Am I missing something or is it the case that the operator should not be
> applied to G?
it is applied to G but via the whitening matrix to which has been applied
hope this helps,
> If the latter is true, why is it true?
> Thanks so much.
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> Mne_analysis at nmr.mgh.harvard.edu
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