[Mne_analysis] Auditory ROI

Bert Liu bert.smt02g at nctu.edu.tw
Sun Dec 9 09:08:57 EST 2018
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Hi, Noa and Alexandre:

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.

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.


Sincerely,
劉柏廷
Bertram Liu

Alexandre Gramfort <alexandre.gramfort at inria.fr> 於 2018年12月8日 週六 下午10:28寫道:

>         External Email - Use Caution
>
> Dear Noa,
>
> can you replicate this with the MNE-sample data that has auditory
> condition?
>
> how did you get the label time course? with
>
>
> https://martinos.org/mne/stable/generated/mne.extract_label_time_course.html
>
> ?
>
> If so with what function?
>
> Alex
> ‪On Thu, Dec 6, 2018 at 8:48 PM ‫נועה הכהן‬‎ <noa1hc at gmail.com> wrote:‬
> >
> >         External Email - Use Caution
> >
> > Hello all,
> > I work on auditory localizer data (when subjects listened to single
> stereo tones), the goal is to define ROI.
> > For doing this, I found the top 0.5% vertixes, and used  grow_labels
>  function.
> > I got nice maps, but when I made a plot of the time course on the left
> and right ROI I got clear auditory ERP on the left hemisphere, and noisy
> and flat signal on the right (figures attached). Those results repeat on
> themselves in some other versions, and for some other similar data sets.
> > Does someone know this phanenomen? any idea?
> > Noa Guttman
> >
> > AL1_al_r_roi.png
> > ‏
> > (55K)
> > AL1_al_l_roi2.png
> > ‏
> > (35K)
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