[FieldTrip] creating leadfiled

[Lilla.Magyari at mpi.nl]

hi,

the singleshell volume conduction model (standard_singleshell) is
implemented for MEG data, while BEM models are used for EEG. It seems to
me that you use EEG template electrodes, therefore those will work only
with EEG volume conduction models. You can look at the reference
documentation of ft_prepare_headmodel
(http://fieldtrip.fcdonders.nl/reference/ft_prepare_headmodel) to see
which headmodels work with which type of data. If you would like to
compute a leadfield with the singlehell model, you need a structure with
gradiometer definition in the cfg.grad instead of the EEG electrode
definition in cfg.elec.

I hope this helps.

Best,
Lilla


>  Dear Fieldtrip experts,
> I would like to create a leadfield based on the standard brain provided
> by the fieldtrip package and standard electrode positions.
> I do it like this :
>       load standard_singleshell  % from template\headmodel
>     cfg                         = [];
> cfg.elec                 = sens;% also from template
>  cfg.vol                   = vol;
>  cfg.reducerank      = 3;
> cfg.grid.resolution = 1;
> [grid]                  = ft_prepare_leadfield(cfg);
>
> Finally I got the following error message.
> converting units from 'mm' to 'cm'
> ??? Error using ==> ft_prepare_vol_sens at 495
> unsupported volume conductor model for EEG
> Error in ==> prepare_headmodel at 84
> [vol, sens] = ft_prepare_vol_sens(vol, sens, 'channel',
> cfg.channel, 'order', cfg.order);
> Error in ==> ft_prepare_leadfield at 147
> [vol, sens, cfg] = prepare_headmodel(cfg, data);
>
> but when I use  'standard_bem' (from template )is OK .
>
>  Is anybody out there who could provide some support?
> Thank you very much in advance,
>  Best,
> mengtongxiao
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