[Mne_analysis] equivalence of averaged single trial STCs and evoked STCs

[Denis-Alexander Engemann]

[reposted, attachment failure]

Hi Dan,

that was indeed a very good hint.

I've updated the gist to do some more systematic comparisons between
orientations and methods:

https://gist.github.com/dengemann/9470121

As to you clarification questions, the lines referred to in the legend  as
'single*' are related to averaging in source space.

It seems using MNE and with a post-hoc normalization, e.g. using z-scores
might be the way to go.
>From my ad-hoc parameter experiment I cannot exclude the possibility, that
'dSPM' and 'sLORETA' with 'normal' orientation might work as well.
This would require a mean-flip method though which is not implemented in my
script due to the manual extraction used.
My extraction function, here, was `lambda x: np.abs(x).mean(0)`

This needs more investigation + discussion

Denis


Images:

https://www.dropbox.com/s/e4ykrm6xdh6ntio/fig-None-MNE.png

https://www.dropbox.com/s/qwlt5ugxxo0owo2/fig-normal-MNE.png

https://www.dropbox.com/s/mijmz9pvffgt5ms/fig-None-sLORETA.png

https://www.dropbox.com/s/8dxf0czptuhyybs/fig-normal-sLORETA.png

https://www.dropbox.com/s/hxcjla8x9euwzd3/fig-None-dSPM.png

https://www.dropbox.com/s/e5pbr7iyday3za4/fig-normal-dSPM.png




On Mon, Mar 10, 2014 at 7:13 PM, dgw <dgwakeman at gmail.com> wrote:

> Hi Denis,
>
> Which line represents "averaging in source space" and which represents
> "projecting evokeds"?
>
> Regardless. I think you are referring to why are the results different
> when I average single trial data on the source space as opposed to
> averaging that same data in sensor space and then source localizing?
>
> The first reason I can think of is that you are using the dSPM here and I
> believe that that can lead to some non-linearity between these results. Do
> you get the same problem with the L2?
>
>  HTH,
> D
>
>
> On Mon, Mar 10, 2014 at 1:56 PM, Denis-Alexander Engemann <
> denis.engemann at gmail.com> wrote:
>
>> Hi folks,
>>
>> in one of my recent analyses I ran into some problems with regard to
>> morphing and single trial
>> label time series extraction which lead me to set up some comparisons:
>>
>> https://gist.github.com/dengemann/9470121
>>
>> (gist based on sample data, should run with a proper MNE-Python install)
>>
>> [image: Inline image 1]
>>
>> It turned out morphing was unproblematic, but,
>> I'm wondering whether the differences between averaging in source space
>> and
>> projecting evokeds is expected, and if so, how it can be avoided?
>>
>> The background is that I'd like to be confident about the relating single
>> trial analyses at the evoked level.
>>
>> Any thoughts?
>>
>> Cheers,
>> Denis
>>
>>
>>
>>
>> _______________________________________________
>> 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
>> in 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...
URL: http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20140310/5d1f8647/attachment.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot 2014-03-10 18.52.06.png
Type: image/png
Size: 88129 bytes
Desc: not available
Url : http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20140310/5d1f8647/attachment.png