[FieldTrip] Precisions on DICS beamforming on EEG data and using normalisation
mpcoll at mac.com
Mon Mar 13 13:47:25 CET 2017
Dear Fieldtrip Community,
My name is Michel-Pierre Coll and I am a postdoctoral researcher at
King's college London.
A reviewer recently suggested we perform DICS beamforming to source
localise EEG effects in the frequency domain during an action
observation/execution paradigm. I was able to perform these analyses
using the very good tutorial on the Fiedltrip website. However, I have
some questions regarding these analyses. I have searched the literature
and the mailing list but somehow I can't find clear answers to these
1) Is it appropriate to perform DICS beamforming using EEG with 60
channels (standard montage) ? If not, what would be the appropriate
number of channels ? Can you suggest a reference discussing this issue ?
2) When not using a contrast to perform the beamforming, is the
normalisation of the lead field an adequate procedure to correct for the
depth/centre bias ? The Fieldtrip tutorial suggest it is but other posts
on the mailing list suggest that it is not.
3) How does one choose an optimal time window for DICS beamforming when
the duration of the effect is quite long (e.g. several seconds of alpha
changes in response to a visual stimulus) ? Is it correct to use a
longer time-window (e.g. 2 seconds) that is representative of the
duration of the effect ?
I would greatly appreciate any hints on these questions or if you could
point me towards relevant texts discussing these issues.
More information about the fieldtrip