[FieldTrip] Baseline Correction using 'relchange' or 'db'

[Eelke Spaak]

Dear Mick,

If you want to run statistics on baseline-corrected time-frequency
data, you should apply ft_freqbaseline on your data before entering it
into ft_freqstatistics. Let us know if that solves the problem.

Best,
Eelke

On 29 July 2015 at 14:55, mick.lehmann at uzh.ch <mick.lehmann at uzh.ch> wrote:
> Dear Fieltrippers,
>
> yesterday I addressed this mailing list with an issue regarding the baseline
> correction for time frequency analysis. While plotting a comparison of two
> conditions revealed exactly the results I've expected, the statistic didn't
> at all. Regardless of electrode, time window and freq range, the comparison
> of the two conditions was significantly different (with t-values between 8
> and 10 and p < 0.001). Digging a little deeper, the main difference between
> the script for plotting and the one for stat analysis is that in for the
> figure, I've to indicate again the baselinewindow and the baselinetype:
>
>
> diff = gaTF_Cond1;
> diff.powspctrm = (gaTF_Cond1.powspctrm - gaTF_Cond2.powspctrm);
>
>
> cfg = [];
> cfg.baseline     = [-1 -.1];
> cfg.baselinetype = 'db';
> cfg.maskstyle    = 'saturation';
> cfg.zlim         = [-3 3];
> cfg.ylim         = [2 25];
> cfg.xlim         = [-1 2];
> cfg.channel       = {'all'};
> cfg.layout =
> 'C:\Users\MickLehmann\Documents\Emo_React_EEG\FieldTrip\Scripts\egi128_GSN_HydroCel3.sfp';
> cfg.interactive = 'yes'
> ft_multiplotTFR(cfg,diff);
>
> Runningit like this, the figure looks fine. However, if I switch off the
> bold part, the figure is dark red (as the stat analysis would suggest).
>
> In the statistic script, I don't indicate the baseline again and I've no
> clue how to implement it. Do you think that could be the problem and has
> anybody a suggestion how to address the problem?
>
> If that is actually the main issue then I'm hardly the first encountering
> this problem.
>
> Kind regards,
> Mick