[FieldTrip] MNE Source Reconstruction Sanity Check

Lozano Soldevilla, D. (Diego) d.lozanosoldevilla at fcdonders.ru.nl
Wed Jul 23 16:35:23 CEST 2014


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 ----- Original Message -----
>From roeysc at gmail.com  Mon Jul 21 11:21:32 2014From: roeysc at gmail.com (Roey Schurr)Date: Mon, 21 Jul 2014 12:21:32 +0300Subject: [FieldTrip] MNE Source Reconstruction Sanity CheckMessage-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 thesource reconstruction activity using the *mne* (minimum norm estimate)method, a *template MRI* (Colin27) and a *singlesphere* headmodel. As asanity check for the source reconstruction itself, I wanted to compareconditions 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 secondseach.2) For each trial, average the activity in each of the 90 ROIs of the aalatlas (I excluded the cerebellum from the source reconstruction).I was wondering what comparison would be best in this case. Since this isnot Evoked Responses data, I find it hard to find relevant ideas, and wouldlike to hear your thoughts.1) I did a frequency analysis (mtmfft) in conventional bands of interestand ran ft_freqstatistics on the resulting structures (using ttest2 and thebonferoni correction for the multiple comparison problem). This gave someresults, however for most conditions they are not very encouraging (theROIs that showed significant differences were not close to those that Ihave assumed).*QUESTION 1*: do you think this is a proper method? Note that I did not usea frequency based source reconstruction in the first place, because I'multimately interested in the time course in the source space.2) I was wondering if a cluster based permutation test is impossible to usehere, since this is a continuous recording, so clustering according to timeadjacency 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 inthe atlas ROIs, which could mask some of the effects, if they are locatedin a small area.3) Another possibility is looking at the data itself. Unfortunately Iencountered some problems using ft_sourcemovie, though this is a subjectfor a different thread.Any thoughts and advice are highly appreciated!Thank you for taking the time,roey
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