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<p class="MsoNormal"><span style="font-family: Calibri;">Dear </span><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">Michael,
</span></p>
<p class="MsoNormal"><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">I did normalize the data
</span></p>
<p class="MsoNormal" style=""><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">(</span><span style="font-size: 10pt; font-family: Courier; color: black;">sourcepst.avg.nai=sourcepst.avg.pow./sourcepre.avg.pow</span><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">)
</span></p>
<p class="MsoNormal" style=""><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">as it was suggested in the tutorial.<span style="">
</span></span><span style="font-family: Courier;"></span></p>
<p class="MsoNormal"><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">I used the same scales in all plots for comparison purposes. If<span style="">
</span>automatic scaling is used the result for MAG+GRA does not look any better (see attachment).
</span></p>
<p class="MsoNormal"><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal"><span style="font-size: 9pt; font-family: Verdana; background: none repeat scroll 0% 0% white;">>What you could do as a workaround is to average the separate results with a weighting per voxel and that >is corresponding to the squared
norms of the leadfields for the respective modalities for a given voxel , this >would guarantee equal amounts of backprojected noise from both modalities (if I'm not mistaken).</span></p>
<p class="MsoNormal"><span style="font-size: 9pt; font-family: Verdana; background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal" style=""><span style="font-size: 9pt; font-family: Verdana; background: none repeat scroll 0% 0% white;">Thank you for your suggestion.<span style="">
</span>I may use it as a last resort.<span style=""> </span>Hopefully, there is still a way to get more optimal solution using both GRA and MAG in the same analysis...</span></p>
<p class="MsoNormal"><span style="font-size: 9pt; font-family: Verdana; background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal"><span style="font-size: 9pt; font-family: Verdana; background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal"><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">Elena</span></p>
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<div style="direction: ltr;" id="divRpF587609"><font color="#000000" face="Tahoma" size="2"><b>From:</b> fieldtrip-bounces@donders.ru.nl [fieldtrip-bounces@donders.ru.nl] on behalf of Elena Orekhova [Elena.Orekhova@neuro.gu.se]<br>
<b>Sent:</b> Thursday, June 02, 2011 6:22 PM<br>
<b>To:</b> Email discussion list for the FieldTrip project<br>
<b>Subject:</b> Re: [FieldTrip] combining magnetometers and planad gradiometers for analysis<br>
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<p class="MsoNormal"><span style="font-family: Calibri;">Dear </span><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">Michael,
</span></p>
<p class="MsoNormal"><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal"><span style="font-family: Calibri; background: none repeat scroll 0% 0% white;">I have tried to multiply the leadfield by -1 as you suggested:</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: Calibri; color: rgb(31, 73, 125); background: none repeat scroll 0% 0% white;"> </span></p>
<p class="MsoNormal" style=""><span style="font-size: 10pt; font-family: Courier; color: blue;">for</span><span style="font-size: 10pt; font-family: Courier; color: black;"> i = 1 : size (grid.leadfield, 2)</span><span style="font-family: Courier;"></span></p>
<p class="MsoNormal" style=""><span style="font-size: 10pt; font-family: Courier;"><span style="">
</span>grid.leadfield{i}(3:3:306, :) = -1*grid.leadfield{i}(3:3:306, :);</span><span style="font-family: Courier;"></span></p>
<p class="MsoNormal" style=""><span style="font-size: 10pt; font-family: Courier; color: blue;">end</span><span style="font-family: Courier;"></span></p>
<p class="MsoNormal" style=""><span style="font-family: Calibri;"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: Calibri;">This had no effect on the
</span><span style="font-family: Calibri; color: rgb(160, 32, 240);">'lcmv'</span><span style="font-family: Calibri;"> output. I attached the pictures for ‘GRA only, ’MAG only’ and ‘GRA + MAG’</span></p>
<p class="MsoNormal"><span style="font-family: Calibri;"> </span></p>
<p class="MsoNormal"><span style="font-family: Calibri;">In this experiment I measured evoked field in response to
<span style=""> </span>the unilateral (left) click. </span></p>
<p class="MsoNormal"><span style="font-family: Calibri;">The source is expected to be in the right superior temporal cortex.
<span style=""> </span>This is the case <span style=""> </span>for </span><span style="font-family: Calibri;"><span style=""> </span>‘GRA only' and ’MAG only’ datasets. The combined sensors give meaningless result.</span></p>
<p class="MsoNormal"><span style="font-family: Calibri;"> </span></p>
<p class="MsoNormal"><span style="font-family: Calibri;">Elena</span></p>
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<div id="divRpF409531" style="direction: ltr;"><font color="#000000" face="Tahoma" size="2"><b>From:</b> fieldtrip-bounces@donders.ru.nl [fieldtrip-bounces@donders.ru.nl] on behalf of Michael Wibral [michael.wibral@web.de]<br>
<b>Sent:</b> Wednesday, June 01, 2011 4:04 PM<br>
<b>To:</b> Email discussion list for the FieldTrip project<br>
<b>Subject:</b> Re: [FieldTrip] combining magnetometers and planad gradiometers for analysis<br>
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<div>Dear Elena,<br>
<br>
could you give the following a try: invert (*-1) the leadfileds for one of the two sensor types. Let me know what happens.<br>
I would also be interested in taking a look at the results - maybe you could sent images off-list: Michael.Wibral <at> web.de.<br>
<br>
Michael<br>
<br>
<br>
<br>
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<b>Von:</b> "Elena Orekhova" <Elena.Orekhova@neuro.gu.se><br>
<b>Gesendet:</b> Jun 1, 2011 12:23:29 PM<br>
<b>An:</b> "fieldtrip@donders.ru.nl" <fieldtrip@donders.ru.nl><br>
<b>Betreff:</b> [FieldTrip] combining magnetometers and planad gradiometers for analysis<br>
<br>
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<p><span style="font-size: 12pt; font-family: Arial;">Dear fieldtrippers, </span>
</p>
<p class="MsoNormal" style=""><span style="font-family: Arial;">This message is mainly for Neuromag users.
</span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;">When I do<span style="">
</span>'lcmv' beamforming analysis separately on planar gradiometers or magnetometers, I get quite meaningful results.</span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;">If I combine the two types of sensors without weighting, the result is meaningless.</span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;">Apparently, the algorithm does not take care of different scales and units of the GRA and MAG measurements.<span style="">
</span>Does anybody know how to deal with this problem?</span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: Arial;">Elena</span></p>
<p><span style="font-size: 12pt; font-family: Arial;"> </span></p>
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