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

[Mark Woolrich]

Dear Hatieng,

This might be the same issue we found when comparing eyes open to eyes shut. Take a look at this technical note to see how we addressed it:
http://www.ncbi.nlm.nih.gov/pubmed/24412400

Cheers, Mark.

On 5 Jan 2015, at 14:23, Haiteng Jiang <haiteng.jiang at gmail.com<mailto:haiteng.jiang at gmail.com>> wrote:

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!
      <resting_issues.jpg>


                                                            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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