<div dir="ltr">Hi Arjen,<div> 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.</div><div><br></div><div> All the best,</div><div> Haiteng </div><div><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><br>
<br>
Message: 2<br>
Date: Mon, 5 Jan 2015 14:39:25 +0000<br>
From: "Stolk, A. (Arjen)" <<a href="mailto:a.stolk@fcdonders.ru.nl">a.stolk@fcdonders.ru.nl</a>><br>
To: FieldTrip discussion list <<a href="mailto:fieldtrip@science.ru.nl">fieldtrip@science.ru.nl</a>><br>
Subject: Re: [FieldTrip] Opposite DICS Beamforming results on source<br>
and sensor level on resting state data<br>
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Hey Haiteng,<br>
<br>
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.<br>
<br>
Yours,<br>
Arjen<br>
<br>
--<br>
Donders Institute for Brain, Cognition and Behaviour<br>
Centre for Cognitive Neuroimaging<br>
Radboud University Nijmegen<br>
<br>
Email: <a href="mailto:a.stolk@donders.ru.nl">a.stolk@donders.ru.nl</a><mailto:<a href="mailto:a.stolk@donders.ru.nl">a.stolk@donders.ru.nl</a>><br>
Phone: +31(0)243 68294<br>
Web: <a href="http://www.arjenstolk.nl" target="_blank">www.arjenstolk.nl</a><<a href="http://www.arjenstolk.nl" target="_blank">http://www.arjenstolk.nl</a>><br>
________________________________<br>
From: <a href="mailto:fieldtrip-bounces@science.ru.nl">fieldtrip-bounces@science.ru.nl</a> [<a href="mailto:fieldtrip-bounces@science.ru.nl">fieldtrip-bounces@science.ru.nl</a>] on behalf of Haiteng Jiang [<a href="mailto:haiteng.jiang@gmail.com">haiteng.jiang@gmail.com</a>]<br>
Sent: Monday, January 05, 2015 3:23 PM<br>
To: <a href="mailto:fieldtrip@science.ru.nl">fieldtrip@science.ru.nl</a><br>
Subject: [FieldTrip] Opposite DICS Beamforming results on source and sensor level on resting state data<br>
<br>
Hi all,<br>
<br>
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<br>
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 (<a href="http://mailman.science.ru.nl/pipermail/fieldtrip/2011-May/003875.html" target="_blank">http://mailman.science.ru.nl/pipermail/fieldtrip/2011-May/003875.html</a>). Thus, I am not the only one who encountered this problem.<br>
<br>
Any tips and suggestions will be greatly appreciated. Thanks in advance!<br>
[cid:ii_i4jxr2sz1_14aba77f4264462a]<br>
<br>
<br>
Best,<br>
Hatieng<br>
<br>
<br>
<br>
<br>
<br>
<br>
--<br>
Haiteng Jiang<br>
PhD candidate<br>
Donders Institute for Brain, Cognition and Behaviour<br>
Neuronal Oscillations Group<br>
Computational Cognitive Neuroscience Lab<br>
<a href="https://sites.google.com/site/haitengjiang/" target="_blank">https://sites.google.com/site/haitengjiang/</a><br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div>Haiteng Jiang </div><div>PhD candidate</div><div>Donders Institute for Brain, Cognition and Behaviour</div><div>Neuronal Oscillations Group </div><div>Computational Cognitive Neuroscience Lab</div></div><div><font face="arial, helvetica, sans-serif"><a href="https://sites.google.com/site/haitengjiang/" target="_blank">https://sites.google.com/site/haitengjiang/</a></font></div></div></div>
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