[Mne_analysis] SSP projection and the forward gain matrix

Alexandre Gramfort alexandre.gramfort at telecom-paristech.fr
Tue Jul 1 10:42:28 EDT 2014
Search archives:

hi Ying,

> 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
the SSPs.

hope this helps,


> If the latter is true, why is it true?
> Thanks so much.
> Best,
> Ying
> _______________________________________________
> Mne_analysis mailing list
> Mne_analysis at nmr.mgh.harvard.edu
> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis
> The information in this e-mail is intended only for the person to whom it is
> addressed. If you believe this e-mail was sent to you in error and the
> e-mail
> contains patient information, please contact the Partners Compliance
> HelpLine at
> http://www.partners.org/complianceline . If the e-mail was sent to you in
> error
> but does not contain patient information, please contact the sender and
> properly
> dispose of the e-mail.

More information about the Mne_analysis mailing list