[FieldTrip] 1. help with output structure of 'ft_sourceanalysis' (Sajeev Kunjan)

Radha Kumari (PGR) 2375059K at student.gla.ac.uk
Mon Jul 4 17:20:37 CEST 2022


Filters can be used to get the individual trials source time series. To get source time series at each of the 6804 voxels, multiply the channel time series by your filter to get sources in x, y and z direction. There are other ways to work with it as well.

Radha

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Today's Topics:

   1. help with output structure of 'ft_sourceanalysis' (Sajeev Kunjan)


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Message: 1
Date: Sun, 3 Jul 2022 23:05:22 +0930
From: Sajeev Kunjan <sajeevckunjan at gmail.com>
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] help with output structure of 'ft_sourceanalysis'
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	<CAGHtspnd05fM2714_0WuzistKiHtVVfd2WnN719f4qqopw9CtQ at mail.gmail.com>
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Dear Fieldtrip,

As part of my research I am using fieldtrip to do connectivity analysis.
But I am really struggling to get my code working.If someone is able to help me with the question below it would be a great help.

Basically what I want to understand, what each field of the output of 'ft_sourceanalysis' means, especially 'trial.filter'.


My intermediate output structure and configurations are shown below. It is a 108 channel 50001 sample EEG time series.




data
-----

    sampleinfo: [1 50001]
       fsample: 5000
          elec: [1×1 struct]
           hdr: [1×1 struct]
         trial: {[108×50001 double]}
          time: {[1×50001 double]}
         label: {108×1 cell}
           cfg: [1×1 struct]


timelock
--------
cfg = [];
cfg.channel = 'EEG';
cfg.vartrllength = 2;
cfg.covariance = 'yes';
cfg.covariancewindow = 'all';
cfg.keeptrials = 'yes';

timelock = ft_timelockanalysis(cfg, data);

timelock =
  struct with fields:

      time: [1×50001 double]
     label: {108×1 cell}
      elec: [1×1 struct]
     trial: [1×108×50001 double]
    dimord: 'rpt_chan_time'
       cov: [1×108×108 double]
       cfg: [1×1 struct]



leadfield
---------
grid = ft_prepare_leadfield( cfg, timelock);

grid =
  struct with fields:

                pos: [6804×3 double]
               unit: 'mm'
                dim: [18 21 18]
             inside: [6804×1 logical]
                cfg: [1×1 struct]
          leadfield: {1×6804 cell}
              label: {108×1 cell}
    leadfielddimord: '{pos}_chan_ori'


source analysis
-----------------
cfg = [];
cfg.channel = 'EEG';
cfg.method = 'lcmv';
cfg.sourcemodel = grid;
cfg.headmodel = vol;
cfg.rawtrial = 'yes';
cfg.lcmv.keepfilter = 'yes';
cfg.keepleadfield = 'yes';
cfg.lcmv.projectnoise = 'yes';
cfg.lcmv.lambda = '2%';
source = ft_sourceanalysis( cfg, timelock);

source =
  struct with fields:

               time: [1×50001 double]
                cfg: [1×1 struct]
                dim: [18 21 18]
             inside: [6804×1 logical]
              label: {108×1 cell}
          leadfield: {1×6804 cell}
    leadfielddimord: '{pos}_chan_ori'
                pos: [6804×3 double]
             method: 'rawtrial'
              trial: [1×1 struct]
                 df: 1


I am trying to understand the content of source.trial(1).filter, which is a cell array of size{6804×1 cell}, each cell has metrics of size 3x108.


Thanks for your help in Advance.

Sajeev Kunjan
PhD Scholar, Flinders university
Adelaide, South Australia
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