[Mne_analysis] how to extract the label time series using MNE-toolbox

junpeng.zhang junpeng.zhang at gmail.com
Wed Mar 19 07:47:04 EDT 2014
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Hi Alex, 

Thank you for kind response.
I still have a question. Please see the highlighted fonts.


> Recently I am conducting an epilepy MEG analysis project. 
> I used MNE toolbox to create a cortex constrained source space (5891 
> sources) and calculated the lead fead matrix (free orientaion, 5891 
> (sources) x 3 (directions xyz) x 306 (channels) matrix ). 
> By on house code, I applied  the inverse problem (beamformer) operator to a 
> segment of epileptiform MEG and then got a 5891 (sources) x 3 (directions) x 
> 500 (time points) matrix (SDTM), which is source time series. 

so you have 3 time series per location. Which is not make stc contain. 

> My questions are as, 
> 1) how to get the information on which source belong to which regions by 
> label operations (for example source A  is included in temporal cortex). If 
> I got such information, I can get a collective time series for a region by 
> averaging (or other ways to get a representative time series) all the source 
> time series in this region. anyone have a quick code  to share it to me? 

if you use instances of SourceEstimates (stc objects) you can use labels. 
I assume you use a surface source space. You can look at the code 
of the in_label method. 

http://martinos.org/mne/stable/generated/mne.SourceEstimate.html#mne.SourceEstimate.in_label 

> 2) epileptiform MEG is difficult to average. and for such MEG, we have only 
> one "trial".  MNE python is quite suitable to process multiple trials MEG 
> data. How to use the several functions to process single "trials" 
> epileptiform MEG? 
> for example, 
> if I know SDTM in matlab format, how to use it as the input of the function 
> mne.extract_label_time_course? 
> The stcs para equals to the SDTM? 

you can get an Evoked instance by average a single Epoch. 
I ever tried to create a instance but in the epilepy raw data,  there is no any events  writed in the file. 
When I import  a .eve file, the error will be no event to average... 
How to transform a  raw.fif into a  ave.fif when the raw file has no events indicated? 
My epilepsy raw file info: 11s ----702s. 

Best wishes, 
Junpeng Zhang


> The following is the three examples for the functions extracted from 
> http://martinos.org/mne/stable/auto_examples/connectivity/plot_mne_inverse_label_connectivity.html#example-connectivity-plot-mne-inverse-label-connectivity-py 
> 
> stcs = apply_inverse_epochs(epochs, inverse_operator, lambda2, method, 
>                             pick_ori="normal", return_generator=True) 
> 
> # Get labels for FreeSurfer 'aparc' cortical parcellation with 34 
> labels/hemi 
> labels, label_colors = mne.labels_from_parc('sample', parc='aparc', 
>                                             subjects_dir=subjects_dir) 
> 
> # Average the source estimates within each label using sign-flips to reduce 
> # signal cancellations, also here we return a generator 
> src = inverse_operator['src'] 
> label_ts = mne.extract_label_time_course(stcs, labels, src, 
> mode='mean_flip', 
>                                          return_generator=True) 

it does not make sense to you mean_flip unless you have fixed orient 
source space 
or used pick_ori='normal'. You can just average you have positive 
values in the stc. 

Hope this helps, 

Alex 
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