[FieldTrip] MNE Source Reconstruction Sanity Check

[Roey Schurr]

Dear Jim,
Thank you for drawing my attention to this problem. I have actually tried
building a realistic head model using OPENMEG but encountered some
compitability problems since our lab does not use Linux. This is indeed one
of the most important (short) future tasks - being able to use such
realistic head models.
Best,
roey


On Thu, Jul 24, 2014 at 6:34 PM, E688205 <j.herring at fcdonders.ru.nl> wrote:

> Dear Roey,
>
> To add to Diego's comments, since you are dealing with EEG data a single
> sphere headmodel is not a good idea because it does not take into account
> the differences in conductivity between the skull, scalp, and brain. This
> is not a problem for MEG but is important for EEG. Therefore it is better
> to use, for example, a BEM head model.
>
> Best,
>
> Jim
>
> On 23 jul. 2014, at 16:38, "Lozano Soldevilla, D. (Diego)" <
> d.lozanosoldevilla at fcdonders.ru.nl> wrote:
>
> Dear Roey,
>
> In my opinion it's definitely not a good idea to compute MNE using 19
> sensors. There are studies that have found a drastic localization precision
> from 31 to 63 electrodes and further improvements till 123:
>
> http://www.ncbi.nlm.nih.gov/pubmed/15351361 (see figure 1)
> http://www.ncbi.nlm.nih.gov/pubmed/12495765
>
> Although it's very difficult to know the "minimum" number of electrodes
> needed to accurately localize a given source (it depends on the strength of
> the source you want to localize, source reconstruction algorithm, data
> noise...), 19 electrodes are too low to trust the results you can get.
>
> best,
>
> Diego
>
>
> ------------------------------
>
> From roeysc at gmail.com  Mon Jul 21 11:21:32 2014
> From: roeysc at gmail.com (Roey Schurr)
> Date: Mon, 21 Jul 2014 12:21:32 +0300
> Subject: [FieldTrip] MNE Source Reconstruction Sanity Check
> Message-ID: <CAHm4wZBRYo4fV63EL9yXaAQ_W43cHF_8J2b+rNyzd55x4aRviw at mail.gmail.com>
>
> Dear fieldtrippers,
>
>
>
> I want to do a sanity check on mne source reconstruction.
>
> I'm working on continuous EEG recordings (19 electrodes), estimating the
> source reconstruction activity using the *mne* (minimum norm estimate)
> method, a *template MRI* (Colin27) and a *singlesphere* headmodel. As a
> sanity check for the source reconstruction itself, I wanted to compare
> conditions in which I could estimate the loci of significant changes, e.g.:
> rest vs movement of the hand, moving the right hand vs the left hand, etc.
> I have about 60 seconds of recording for each condition.
>
>
>
> What I did was:
>
> 1) Segment the recording of each condition into many "trials" of 2 seconds
> each.
>
> 2) For each trial, average the activity in each of the 90 ROIs of the aal
> atlas (I excluded the cerebellum from the source reconstruction).
>
>
>
> I was wondering what comparison would be best in this case. Since this is
> not Evoked Responses data, I find it hard to find relevant ideas, and would
> like to hear your thoughts.
>
>
>
> 1) I did a frequency analysis (mtmfft) in conventional bands of interest
> and ran ft_freqstatistics on the resulting structures (using ttest2 and the
> bonferoni correction for the multiple comparison problem). This gave some
> results, however for most conditions they are not very encouraging (the
> ROIs that showed significant differences were not close to those that I
> have assumed).
>
>
>
> *QUESTION 1*: do you think this is a proper method? Note that I did not use
> a frequency based source reconstruction in the first place, because I'm
> ultimately interested in the time course in the source space.
>
>
>
> 2) I was wondering if a cluster based permutation test is impossible to use
> here, since this is a continuous recording, so clustering according to time
> adjacency seems irrelevant.
>
>
>
> *QUESTION 2*: is it possible to use a cluster based statistical test here?
> If so, it could be better than a-priori averaging the source activity in
> the atlas ROIs, which could mask some of the effects, if they are located
> in a small area.
>
>
>
> 3) Another possibility is looking at the data itself. Unfortunately I
> encountered some problems using ft_sourcemovie, though this is a subject
> for a different thread.
>
>
>
> Any thoughts and advice are highly appreciated!
>
> Thank you for taking the time,
>
> roey
>
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