FieldTrip

The ft_definetrial and ft_preprocessing functions require the original MEG dataset, which is available from ftp://ftp.fcdonders.nl/pub/fieldtrip/tutorial/Subject01.zip.

% find the interesting segments of data
cfg = [];                                           % empty configuration
cfg.dataset                 = 'Subject01.ds';       % name of CTF dataset  
cfg.trialdef.eventtype      = 'backpanel trigger';
cfg.trialdef.prestim        = 1;
cfg.trialdef.poststim       = 2;
cfg.trialdef.eventvalue     = 5;                    % trigger value for initially congruent (IC)
cfg = ft_definetrial(cfg);            

% remove the trials that have artifacts from the trl
cfg.trl([1, 2, 3, 4, 14, 15, 16, 17, 20, 35, 39, 40, 47, 78, 79, 80, 86],:) = []; 

% preprocess the data
cfg.channel    = {'MEG', '-MLP31', '-MLO12'};        % read all MEG channels except MLP31 and MLO12
cfg.demean     = 'yes';
cfg.baselinewindow  = [-0.2 0];
cfg.lpfilter   = 'yes';                              % apply lowpass filter
cfg.lpfreq     = 35;                                 % lowpass at 35 Hz.

dataIC_LP = ft_preprocessing(cfg);                      

These data have been cleaned from artifacts by removing several trials and two sensors; see the visual artifact rejection tutorial.

Subsequently you can save the data to disk.

save dataIC_LP dataIC_LP