<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style id="owaParaStyle" type="text/css">P {margin-top:0;margin-bottom:0;}</style>
</head>
<body ocsi="0" fpstyle="1">
<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">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>
<div><br>
<div style="font-family:Tahoma; font-size:13px">
<div style="font-family:Tahoma; font-size:13px">--<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" target="_blank">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></div>
</div>
</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">
<hr tabindex="-1">
<div style="direction: ltr;" id="divRpF292681"><font color="#000000" size="2" face="Tahoma"><b>From:</b> fieldtrip-bounces@science.ru.nl [fieldtrip-bounces@science.ru.nl] on behalf of Haiteng Jiang [haiteng.jiang@gmail.com]<br>
<b>Sent:</b> Monday, January 05, 2015 3:23 PM<br>
<b>To:</b> fieldtrip@science.ru.nl<br>
<b>Subject:</b> [FieldTrip] Opposite DICS Beamforming results on source and sensor level on resting state data<br>
</font><br>
</div>
<div></div>
<div>
<div dir="ltr">Hi all,
<div><br>
</div>
<div> 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
<div>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 (<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.</div>
<div> </div>
<div> Any tips and suggestions will be greatly appreciated. Thanks in advance!</div>
<div> <img src="cid:ii_i4jxr2sz1_14aba77f4264462a" height="562" width="537"><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div> Best,</div>
<div> Hatieng</div>
<div> </div>
<div> </div>
<div><br>
</div>
<div> </div>
<div> <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>
</div>
</div>
</div>
</div>
</div>
</div>
</body>
</html>