[FieldTrip] Opposite DICS Beamforming results on source and sensor level on resting state data (Stolk, A. (Arjen))

[Haiteng Jiang]

Hi Arjen,
    Thanks for your response.  I actually tried both (absolute power and
nai).  Both of them are  still opposite when comparing  sensor level to
source level.  Besides,  I have  the task  data. It works fine on the
contrast.  Therefore, I assume the co-registration is OK in general.
However,  I have no fiducial points in the MRI scans, so I have to select
the nas, lpa and rpa with no physical reference.  Therefore , it is
possible that the two group have systematic differences in head position. I
will check that.

                                                     All the best,
                                                      Haiteng

>
>
> Message: 2
> Date: Mon, 5 Jan 2015 14:39:25 +0000
> From: "Stolk, A. (Arjen)" <a.stolk at fcdonders.ru.nl>
> To: FieldTrip discussion list <fieldtrip at science.ru.nl>
> Subject: Re: [FieldTrip] Opposite DICS Beamforming results on source
>         and sensor level on resting state data
> Message-ID:
>         <B1E918C91415AC4B9437A1EEC90D79AFCDBB2E at exprd01.hosting.ru.nl>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hey Haiteng,
>
> Is your contrast based on absolute signal frequency power? If so, did you
> check for any systematic differences in headposition (and especially in
> terms of distance to the sensors - the z-dimension) across the groups? I
> presume such a systematic difference could yield different results at the
> sensor- and source-level, but there are probably also other possibilities
> out there.
>
> Yours,
> Arjen
>
> --
> Donders Institute for Brain, Cognition and Behaviour
> Centre for Cognitive Neuroimaging
> Radboud University Nijmegen
>
> Email:  a.stolk at donders.ru.nl<mailto:a.stolk at donders.ru.nl>
> Phone:  +31(0)243 68294
> Web:    www.arjenstolk.nl<http://www.arjenstolk.nl>
> ________________________________
> From: fieldtrip-bounces at science.ru.nl [fieldtrip-bounces at science.ru.nl]
> on behalf of Haiteng Jiang [haiteng.jiang at gmail.com]
> Sent: Monday, January 05, 2015 3:23 PM
> To: fieldtrip at science.ru.nl
> Subject: [FieldTrip] Opposite DICS Beamforming results on source and
> sensor level on resting state data
>
> 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 Schr?der 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!
>       [cid:ii_i4jxr2sz1_14aba77f4264462a]
>
>
>                                                             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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-- 
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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