[FieldTrip] lambda value for MNE source reconstruction (Sara Cinelli)

[Richards, John]

Sara.

Having a number, like 3, means that some of the source analysis routines will scale part of the solution relative to error variance..  the ft_sourceanalysis documentation sounds like it does the proportional to the error covariance matrix--by trials?  Other programs use this in the computation of the source inverse, which is "ill-defined", but can be computed in a formula with the lambda.   In the past I have used the actual error covariance to compute a proportional lambda value for some computations.  At some point, due to its superior reconstruction we switched to eLOREATA, which has a lambda but it is not computed on the error variance.

John

***********************************************
John E. Richards
Carolina Distinguished Professor
Department of Psychology
University of South Carolina
Columbia, SC  29208
Dept Phone: 803 777 2079
Fax: 803 777 9558
Email: richards-john at sc.edu
https://jerlab.sc.edu/
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Today's Topics:

   1. lambda value for MNE source reconstruction (Sara Cinelli)
   2. units of measurements from ft_sourceanalysis (Sara Cinelli)
   3. lcmv weightnorm (Edoardo Pinzuti)


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Message: 1
Date: Fri, 27 Sep 2024 14:41:57 +0200
From: Sara Cinelli <sara.cinelli at studenti.unipd.it>
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] lambda value for MNE source reconstruction
Message-ID:
        <CAHrCV41WOo4SowMjCqy+x=SZyXvJvXePWCHg--zHyNMSQP0-Uw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hello everyone,
I have a question regarding the appropriate value for lambda in the MNE source reconstruction. For example, it is not clear to me if exists and if so how can be determined the optimal value for lambda. For example here in the tutorial I saw that the value has been set to 3. (
https://www.fieldtriptoolbox.org/tutorial/minimumnormestimate/#inverse-solution
)
Thank you,

Sara
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Message: 2
Date: Fri, 27 Sep 2024 15:30:46 +0200
From: Sara Cinelli <sara.cinelli at studenti.unipd.it>
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] units of measurements from ft_sourceanalysis
Message-ID:
        <CAHrCV43bvsRweGNW29tnGO2Yjbjz8TauPdte9NKSPFgjsWZ-Sw at mail.gmail.com>
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Hello again,
sorry for this second email.
I would like to ask you about the unit of measurements coming out from the source reconstruction with MNE (method='MNE' with ft_sourceanalysis). The unit of measurements I used in the sourcemodel, headmodel and leadfield are mm and microV [10^-6 V]. The EEG data in input are in microV. I read the email in the discussion list and also the page of explenation on your website, but it is not very clear to me how to keep this important information.
Thanks again,

Sara
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Message: 3
Date: Fri, 27 Sep 2024 18:50:28 +0200
From: Edoardo Pinzuti <edoardo.pinzuti at gmail.com>
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] lcmv weightnorm
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Dear Fieldtrip users,

Do you know why if I use this setting cfg.lcmv.weightnorm = 'nai' for my lcmv beamformer analysis I get complex value avg.mom.

I am doing a lcmv on resting state data and I need the timecourses of specific ROIs is this "nai" parameter required ?

Thanks
Edoardo
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