[Mne_analysis] Auditory ROI

[Bert Liu]

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Hi,

Thanks for your reply, Alex.
Yeah, you might be right.
Noa said "single *stereo* tones", so it may be the correlated sources
problem.

From my experience, dSPM could be stable in some cases of presenting
correlated sources in M/EEG. But the original LCMV beamformer will not be
able to localize and reconstruct the correlated sources because of its
unit-gain constraint and the cancellation phenomenon. Moreover, recently,
some scholars are tackling this problem, so if some people need very
accurate source localization, I would recommend newly advanced algorithms
to them.


Bert


Alexandre Gramfort <alexandre.gramfort at inria.fr> 於 2018年12月9日 週日 下午10:27寫道：

>         External Email - Use Caution
>
> hi,
>
> > This is cancellation phenomenon in signal processing. To be more
> specific in neuroimaging of MEG/EEG, when you send the same sound
> simultaneously to each ear of a subject, like you mentioned single stereo
> tones, there will be temporally correlated sources on bilateral A1s in the
> MEG or EEG signals recorded from the subject. Highly temporally correlated
> sources in an MEG or an EEG will cause the problem you mentioned.
> Furthermore, this phenomenon can be explained by math. So, if you want to
> know more, I can give you some references.
>
> I think that Noa is using MNE-dSPM so I am not sure it is a problem of
> correlated sources.
>
> > Solution to this problem: Noa, you need to use advanced source
> localization algorithms to localize the true source grids and reconstruct
> the distortionless time-courses of correlated sources. But I am not
> familiar with MNE, so I don't know which advanced algorithms are available
> in MNE software to address this problem. However, I know some available
> algorithms in other toolboxes.
>
> see what MNE has in store:
> http://martinos.org/mne/stable/auto_examples/index.html
>
> you can use MNE/dSPM/sLORETA/eLORETA with make_inverse_operator
> you have most beamformers (make_lcmv, make_dics) as well as
> sparsity based solvers that output dipole sets such as mixed_norm,
> tf_mixed_norm, music, gamma_map etc.
>
> Alex
>
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