[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,
best,
Björn
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