[FieldTrip] Opposite DICS Beamforming results on source and sensor level on resting state data

[Haiteng Jiang]

Hi  all,

   I performed DICS beamforming on resting-state data ( eyes closed) of a
clinical population and controls. According to the sensor data,  the
control groups have more alpha-band (8-14
Hz) activity over occipital  areas  after cluster statistic (attached
figure  upper plot) . Curiously, after beamforming ,  group comparisons
showed the reversed patters in visual cortex (attached figure  bottom plot)
.Hence, the source-level results are opposite to the sensor-level results.
This is *not* a problem of the design matrix, or confusing the groups.  I
check  the individual neural  activity index on the single subject level .
  They  make sense in general .  I also tune the parameter a lot (tapper,
central frequency smooth frequency , regularization  parameter , et al ),
the  opposite pattern remains.  I  understand that Beamformer images DO NOT
DIRECTLY CORRESPOND TO ANY sensor data.   However, the opposite pattern is
really weird.  I noticed that  Tobias Navarro Schröder had the similar
issue 4 years ago (
http://mailman.science.ru.nl/pipermail/fieldtrip/2011-May/003875.html).
Thus,  I am not the only one who encountered this problem.

   Any tips and suggestions will be greatly appreciated.  Thanks in advance!



                                                            Best,
                                                            Hatieng






-- 
Haiteng Jiang
PhD candidate
Donders Institute for Brain, Cognition and Behaviour
Neuronal Oscillations Group
Computational Cognitive Neuroscience Lab
https://sites.google.com/site/haitengjiang/
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