[FieldTrip] Scaling issues with EEG time frequency analysis

Arti Abhishek mailtome.2113 at gmail.com
Mon Oct 13 08:49:42 CEST 2014


Dear fieldtrip users,

I am a new fieldtrip user and I am having some problems with frequency
analysis. My EEG data is recorded from Neuroscan NuAmps system (22 bit). I
have used the following script (I wrote the script from the examples on the
fieldtrip website), but I get the time frequency plots with huge values.
Could anyone please suggest me what I am doing wrong?

Thanks
Arti

cfg =[];

cfg.dataset = 's01.cnt';

cfg.channel = {'all'};

cfg.layout = 'NuAmps.lay';

lay = ft_prepare_layout(cfg);

% Event identification

cfg.trialdef.eventtype = 'trigger';

cfg.trialdef.eventvalue = 101;

cfg.trialdef.prestim = 1;

cfg.trialdef.poststim = 2;

cfg.reref = 'yes';

cfg.implicitref = 'A1';

cfg.refchannel = {'A1' 'A2'};

cfg = ft_definetrial(cfg);

% % Filtering

% cfg.hpfilter = 'yes';

% cfg.hpfreq = 0.1;

% cfg.hpfilttype = 'fir';

dataFIC = ft_preprocessing(cfg);

%% Summary detection of bad trials

cfg = [];

cfg.method = 'summary';

cfg.layout = lay; % this allows for plotting

cfg.channels = [1:34];

data_clean = ft_rejectvisual(cfg, dataFIC);

% Calculate TFR for condition1

cfg = [];

cfg.trials = find(data_clean.trialinfo==101);

cfg.channel = 'EEG';

cfg.method = 'wavelet';

cfg.width = 7;

cfg.output = 'pow';

cfg.foi = 2:2:48;

cfg.toi = -0.5:0.05:1;

s01_TFRwave4ch = ft_freqanalysis(cfg, data_clean);

%% Plot TFR

cfg = [];

cfg.baseline = [-0.5 -0.1];

cfg.baselinetype = 'absolute';

cfg.zlim = [-500 500];

cfg.showlabels = 'yes';

cfg.layout = lay;

figure

ft_multiplotTFR(cfg, s01_TFRwave4ch)
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