[FieldTrip] problem with surface Laplacian

[Max Cantor]

It seems like the issue is between the number of channels in your input
(48) is different from the number of channels in the sensor description
(60). You should use ft_channelrepair to interpolate the removed channels,
and then it should work barring any other issues.

On Wed, Dec 17, 2014 at 5:45 AM, Hwee Ling Lee <hweeling.lee at gmail.com>
wrote:
>
> Dear all,
>
> I have 60 channel EEG resting state data, and after discarding bad
> channels, I am left with 48 channels common to all subjects.
>
> I applied scalp current density to my data before extracting power
> information from my EEG data. The EEG cap that I used was in a 10-10
> system, and I don't have the electrode position file. Hence, I used the
> default electrode position file named 'standard_1005.elc' for the purpose.
>
> Here's the part of my script for the surface Laplacian:
>
>
>     cfg_neighb.method = 'template';
>     cfg_neighb.layout = 'EEG1010.lay';
>     cfg_neighb.channel = 'all';
>     cfg_neighb.feedback = 'no';
>
>     neighbours = ft_prepare_neighbours(cfg_neighb, data7);
>
>     cfg                 = [];
>     cfg.method          = 'finite';
>     cfg.elecfile        = 'standard_1005.elc';
>     cfg.elec            = ft_read_sens(cfg.elecfile);
>     cfg.trials          = 'all';
>     cfg.neighbours      = neighbours;
>     cfg.conductivity    = 0.33;
>
>     data8               = ft_scalpcurrentdensity(cfg, data7);
>
> When I tried to extract power from data8 (after surface Laplacian), I keep
> getting an error message (see below). I'm not sure why this would be the
> case, and would appreciate very much if someone could help me resolve the
> error!
>
> Thank you!
>
> Here's my script for extracting the power:
>  cfg                 = [];
>     cfg.output          = 'pow';
>     cfg.channel         = {'all'};
>     cfg.method          = 'mtmfft';
>     cfg.keeptrials      = 'no';
>     cfg.tapsmofrq       = 5;
>     cfg.layout          = 'EEG1010.lay';
>
>     % for frequencies up to 30 Hz
>     cfg.foilim          = [1 30]; % either the full range of frequencies
> (data2.hdr.Fs/2) or up to 100 Hz
>     cfg.taper           = 'hanning';
>
>     % find the index for the c200 condition
>     pre_c200_idx = find(data8.trialinfo == 200);
>     cfg.trials          = pre_c200_idx;
>     LF_pre_c200        = ft_freqanalysis(cfg, data8);
>
> Here's the output plus error message:
>
> the input is raw data with 48 channels and 343 trials
> Error using ft_datatype_sens (line 375)
> inconsistent number of channels in sensor description
>
> Error in ft_datatype_raw (line 138)
>       data.elec = ft_datatype_sens(data.elec);
>
> Error in ft_checkdata (line 223)
>   data = ft_datatype_raw(data, 'hassampleinfo', hassampleinfo);
>
> Error in ft_freqanalysis (line 209)
> data = ft_checkdata(data, 'datatype', {'raw', 'raw+comp', 'mvar'},
> 'feedback',
> cfg.feedback, 'hassampleinfo', 'yes');
>
> Best regards,
> Hweeling
>
>
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>


-- 
Max Cantor
Lab Manager
Computational Neurolinguistics Lab
University of Michigan
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