[FieldTrip] How to impove dics realfilter solution

Björn Herrmann bherrmann at cbs.mpg.de
Fri Sep 14 10:23:14 CEST 2012

Dear fieldtrip user,

I am using the DICS beamformer to localize a 3Hz FFT power topographical distribution (using a neuromag system). The topographies are very clear auditory in single subjects, thus it shouldn't be a problem finding the "right" solution. When I use the beamformer to obtain complex-value spatial filters, the solution looks very good (using NAI). No problem here. However, using cfg.dics.realfilter = 'yes', i.e. the spatial filter will have real values, the localization completely breaks down, sometimes even finding a strong peak in the opposite hemisphere than visible in the sensor topography (the head is centered in the sensor array). 

Does someone have a suggestion how to improve the solution using realfilter = 'yes'. I use the following settings. They are rather standard I guess.

cfg = [];
cfg.method            = 'dics';
cfg.frequency         = 3;
cfg.dics.projectnoise = 'yes';
cfg.dics.lambda       = '5%';
cfg.dics.keepfilter   = 'yes';
cfg.dics.realfilter   = 'yes';
cfg.dics.fixedori     = 'no';

If someone has a suggestion, I would appreciate it.
Thanks in advance,


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