[FieldTrip] questions about topoplot and notch filter

WanYu Hsu wanyu at gazzaleylab.ucsf.edu
Tue Apr 14 00:48:45 CEST 2015

Hi community,

Recently I am analyzing EEG dataset with only 20 channels and I am focusing
on coherence between frontal and posterior electrodes in frequency domain.

I got two questions here:

1. I wanted to topoplot the coherence between each pair of electrodes that
we're interested in, and I tried the following script:

cfg                    = [];
cfg.colorparam = 'plvspctrm';
cfg.layout         = 'biosemi64.lay';
cfg.foi =[4];
ft_topoplotCC(cfg, plv_avg_stim);

The electrode layout and coherence we wanted to see were in the plot, but
the plot did not show coherence related to FP1, FP2, and FPz. Am I doing
something wrong?

2. I would like to apply notch filter to remove 6 Hz and first I tried
cfg.dftfilter ='yes';
cfg.dftfreq = [6]
but the 6Hz signal was still there.

Then I also tried

cfg.bsfilter ='yes';
cfg.bsfreq =[5 7];

This worked well to remove 6Hz signal, but it also affected 5Hz and 7Hz.

Is there any way to remove 6 Hz specificlly?

Any help would be appreciated.


Wanyu Hsu
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