[FieldTrip] Calculating ERPs with tf_timelockbaseline

[Julian Keil]

Dear Luca,

could you be a bit more precise in your description?
By saying that "figure Always turn out the same for each electrode“, do you mean that the ERP is identical at each electrode?
In that case, I suggest going back a step and checking whether the signal at each electrode is identical. That would indicate a problem earlier in your pipeline, e.g. that you overwrite the single electrodes with a common signal.

Or do you mean, that the signal does not change from Color_C to ERP? 
In that case, I suggest inspecting Color_C in close detail, and computing the mean of the baseline interval by hand. If that value is close to zero, you can’t expect drastic changes from the baseline correction.

Hope that helps,

Julian
 
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Prof. Dr. Julian Keil

Biological Psychology
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> Am 09.04.2019 um 10:11 schrieb Luca Moretti <moretti.l1991 at gmail.com>:
> 
> Dear Fieldtrippers,
> 
> I have a problem concerning the calculation of ERPs with ft_timelockbaseline. After I have preprocessed the data (re-referenced, filtered, cleaned from artifact), this is what I have done:
> 
> inputfile = (strcat('Subject_2_clean.mat'));
> load (inputfile);
> layout = 'easycapM1';
> 
> %% Calculating ERP
> 
> cfg = [];
> cfg.trials = find(data_clean_2.trialinfo==60);
> Color_C = ft_timelockanalysis(cfg, data_clean_2);
> 
> %% Plotting
> 
> cfg = [];
> cfg.baseline = [-.3 0];
> cfg.channel = {'all'};
> cfg.parameter = 'avg';
> ERP = ft_timelockbaseline(cfg, Color_C);
> 
> figure
> cfg = [];
> cfg.layout = layout;
> cfg.interactive = 'yes';
> cfg.showoutline = 'yes';
> ft_multiplotER(cfg, ERP)
> 
> %%
> 
> My problem is that it doesn't matter what kind of baseline period I am chosing, the figure Always turn out the same for each electrode. I have even tried to set the baseline to the Whole trial period, but the figure I get from plotting individual channels from the multiplot is Always the same.
> 
> Can someone find something wrong with my code?
> 
> Many thanks!
> Luca
> 
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> https://doi.org/10.1371/journal.pcbi.1002202

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