[FieldTrip] beamformer to localize spontaneous oscillation source

[PWW]

Dear Fieldtrippers,

In the beamformer tutorial (
http://fieldtrip.fcdonders.nl/tutorial/beamformer), the contrast of
(post-pre)/pre was calculated to circumvent the  noise bias towards the
center of the head.

However, I wonder whether it is possible to only localize the pre-stimulus
oscillation source, such as pre-stimulus alpha power for example, just like
localizing the sources of spontaneous oscillatory activity. Actually, I
tried to do it, and use neural activity index to remove the center of the
head bias, by setting setting cfg.dics.projectnoise='yes'. But it doesn't
work so well.

Does anyone have any suggestions about localizing the cortical sources of
spontaneous oscillatory activity (e.g. pre-stimulus interval only)? is it
any difference with the procedures described in the tutorial?

Any pointers would be much appreciated.

Thanks.

Regards,

Weiwei
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