[Mne_analysis] Regularization of the noise covariance matrix with tSSSed data
sheraz at nmr.mgh.harvard.edu
Fri Jul 18 10:56:56 EDT 2014
Rey might pinch in more, my few cents, tsss projection are not orthgonal in
space, so they do not reduce the rank as SSS or PCA, tsss projections
reduces the variance of the first few components, since most rank
determining algoritham uses some sort of ratio of highest to lowest, after
tsss if you try to determine rank in Matlab or python they might give you a
value higher than 64.
Best rank guest should be 64 - all the PCA projection you are using.
On Jul 18, 2014 7:52 AM, "Alexandre Gramfort" <
alexandre.gramfort at telecom-paristech.fr> wrote:
> hi Ying,
> try at first without regularizing. MNE should detect the rank
> automatically when whitening. It's however possible that tSSS makes
> rank estimation difficult due to slight head positions changes.
> maybe Sheraz or Rey can share their insights too.
> On Thu, Jul 17, 2014 at 6:43 PM, Ying Yang
> <evergreenlifeyangying at gmail.com> wrote:
> > Hi MNE experts,
> > I am wondering whether it is common to regularize the noise covariance
> > matrix for tSSSed data. Since tSSS may reduce the rank of the sensor
> > (in my case to 64), the covariance matrix is singular too. As a result,
> > the whitened forward gain matrix had a lot of zeros.
> > In this case, is it better to regularize the noise covariance matrix,
> or to
> > leave it intact such that the rank of noise matches the rank of
> > Thanks in advance!
> > 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
> > error
> > but does not contain patient information, please contact the sender and
> > properly
> > dispose of the e-mail.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Mne_analysis