[FieldTrip] time frequency data looks blocky and stripy rather than smooth and swirly

Poppy Watson popwatson at hotmail.com
Thu Jan 10 05:57:24 CET 2019

Dear fieldtrippers,

I'm replicating a study that used fieldtrip for TF analysis (and has some lovely single electrode TF plots  for each experimental condition). I've been running ft_freqanalysis using the following settings.

cfg = [];
cfg.trials  = trialsToUse; % this is a vector of trial numbers
cfg.method = 'mtmconvol';
cfg.output = 'pow';
cfg.channel = 'eeg';
cfg.taper = 'hanning';
cfg.foi = 2:2:30;
%cfg.t_ftimwin    = 4 ./ cfg.foi;
cfg.t_ftimwin    = ones(length(cfg.foi),1).*0.5;
cfg.toi = -1.25:0.10:0.25;   % 100 ms sliding time window

The output and stats  etc seem to all make sense but my concern is that when I plot the data e.g. from one electrode (collapsed across the whole pp group)- I don't get beautiful fuzzy TF graphs - instead I get very blocky/stripy figures like the attached where there doesn't seem to be any smoothing/bleeding across different frequencies. I've tried playing around with the cfg.foi as well as the length of the time window and sliding window (cfg.t_ftimwin and cfg.toi) but the results always look very blocky rather than all warm and fuzzy (i.e. as seen in raw-TFdata-of-single-electrode images in various publications). Am I missing some smoothing parameters??

This is my singleplot_TFR code:

cfg = [ ] ;
cfg.channel      = 'FCz';
cfg.xlim         = [-1 0]; %before stimulus appears
cfg.ylim         = [2 20]; % [8 12] only alpha
cfg.zlim = [0 15];
cfg.maskstyle    = 'saturation';
cfg.masknans = 'yes';
ft_singleplotTFR(cfg, allPPdata_suc_collapsed_high);

Many Thanks
P. Watson

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