[Mne_analysis] LCMV questions

[Luke Bloy]

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Thanks Britta, that is what I was looking for.

On Tue, Nov 26, 2019 at 11:39 AM Britta Westner <britta.wstnr at gmail.com>
wrote:

>         External Email - Use Caution
>
> Hi Luke,
>
> the data_cov in the LCMV implementation serves the same purpose as
> Fieldtrip's data covariance matrix (i.e., it is used to compute the spatial
> filter). The noise covariance matrix is used to whiten the data, lead
> field, and covariance matrix. This is only mandatory if you supply data
> with several channel types (e.g., MEG and EEG or gradiometers and
> magnetometers) and is used to deal with scaling issues that arise with
> those different channel types.
>
> Hope this helps,
> Britta
>
> On Tue, Nov 26, 2019 at 5:35 PM Luke Bloy <luke.bloy at gmail.com> wrote:
>
>>         External Email - Use Caution
>>
>>
>> I just started looking at the LCMV beamformer implementation in MNE and
>> I'm a bit confused by the use of a 2 covariance matrices.
>>
>> The implementations I'm familiar with (fieldtrip and ctf tools) use a
>> single covariance. So to commute a differential beamformer you need to
>> compute an average covariance (between the active and baseline time
>> windows) to make the filter weights etc.
>>
>> This is the approach taken in this tutorial.
>> http://www.fieldtriptoolbox.org/workshop/aarhus/beamformingerf/
>>
>> Does the MNE implementation do this already? Are the filter weights the
>> same if I switch what I pass in for the data and noise covariances?
>>
>>
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