DICS

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Tue Jul 11 17:51:28 CEST 2006


Dear Muthuraman

On 11 Jul 2006, at 16:59, Muthuraman Muthuraman wrote:
> To use the DICS method
>
> We have a 64 channel EEG measurement from (Neuroscan) and 4 EMG
> channels recording
> and also we have the 64 channel measurement in FRMI
>
> the electrode locations we have it in a file with 3 columns x,y,z
> for each electrode
> using the polhemus sensors but our own software
>
> In the Source analysis
> Cfg.method='DICS';
> but Cfg.xgrid, ygrid and zgrid
> the grid values are the sensor location values
>
> or it should be the
> cfg.grid.pos-where i can give in the 3 values [x y z] for each
> electrode

in SOURCEANALYSIS you specify using cfg.xgrid/ygrid/zgrid the
locations at which the _dipoles_ will be placed, it is not the
position of the electrodes. At each grid location a spatial filter is
constructed and the power (and coherence) is computed. If you do not
want to scan on a full 3-D grid, but on only a few dipole locations
of interest, you can use cfg.grid.pos to specify those dipole locations.

The electrode positions are specified in the cfg.elec structure, or
in the cfg.elecfile filename. You can find more details on the
definition of electrode positions at http://www2.ru.nl/fcdonders/
fieldtrip/doku.php?
id=fieldtrip:documentation:frequently_asked_questions#how_are_electrodes
_magnetometers_or_gradiometers_described

Furthermore, you can try using the READ_FCDC_ELEC function for
reading the electrode locations, but probably taht will not work
since youy are using your own software for digitization.
Alternatively, you can manually construct an "elec" electrode
definition.

best regards
Robert

PS please upgrade to a recent fieldtrip version, the sourceanalysis
options cfg.xgrid/ygrid/zgrid have been renamed. The old options
still will work, but in general it is preferable to work with a
recent copy of the toolbox.



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