<div>Dear Sarang,</div><div><br></div><div>Thanks for your reply.</div><div><br></div><div>Our MEG system consists of 148 magnetometers. I searched the MEG papers published by researchers in your previous department at the University of Konstanz, and found two papers by <span class="s1" style="line-height: 1.5;">Staudigl, </span><span class="s2" style="line-height: 1.5;"><span class="s3">Hanslmayr</span></span><span style="line-height: 1.5;"> and colleagues (2013, 2015), </span><span style="line-height: 1.5;">in which the MEG data were collected with Magnes 2500WH 148-channel system and analyzed by FieldTrip. I'm happy about the papers. It seems that we can also use our MEG system to perform experiments. </span></div><div><span style="line-height: 1.5;"><br></span></div><div><span style="line-height: 1.5;">I'm new to the MEG field and am learning. Actually, I'm not sure about what the balancing weights are for. I read some scripts/functions of the FieldTrip toolbox, such as ft_read_header, bti2grad and read_4d_hdr. It says in the bti2grad function, "</span><span style="line-height: 1.5;">BTI2GRAD converts a 4D header to a gradiometer structure that can be </span><span style="line-height: 1.5;">understood by FieldTrip and Robert Oostenveld's low-level forward and </span><span style="line-height: 1.5;">inverse routines." So my understanding is that the balancing weights stored in hdr.grad is important for carrying out analyses at the source level? Or, the balancing weights are only necessary for gradieometers system but not for magnetometers system?</span></div><div><span style="line-height: 1.5;"><br></span></div><div><span style="line-height: 1.5;">Thanks again for the information.</span></div><div><span style="line-height: 1.5;"><br></span></div><div><span style="line-height: 1.5;">Best wishes,</span></div><div><span style="line-height: 1.5;">Ling</span></div>
<div><includetail><div> </div><div> </div><div style="font:Verdana normal 14px;color:#000;"><div style="FONT-SIZE: 12px;FONT-FAMILY: Arial Narrow;padding:2px 0 2px 0;">------------------ Original ------------------</div><div style="FONT-SIZE: 12px;background:#efefef;padding:8px;"><div id="menu_sender"><b>From: </b> "Sarang S. Dalal"<sarang@cfin.au.dk>;</div><div><b>Date: </b> Wed, May 4, 2016 06:50 PM</div><div><b>To: </b> "FieldTrip discussion list"<fieldtrip@science.ru.nl>; <wbr></div><div></div><div><b>Subject: </b> Re: [FieldTrip] 4D-Neuroimaging Magnes 2500WH system</div></div><div> </div>
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<p>Dear Ling,<br>
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<p><span style="font-size: 12pt;">Does your system consist of 148 magnetometors or gradiometers? In my previous lab at the University of Konstanz, we also had the Magnes 2500WH with 148 magnetometers. In our experience, the weights were not necessary for analyses
at either the sensor or source level. If your system consists of gradiometers, however, maybe these weights would be necessary?</span></p>
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<p><span style="font-size: 12pt;">If you really need those weights, I believe you can find them in the header structure, somewhere in data.hdr.orig. You will then need some knowledge on how to apply those weights.</span></p>
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<p><span style="font-size: 12pt;">Cheers,</span></p>
<p><span style="font-size: 12pt;">Sarang</span></p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> fieldtrip-bounces@science.ru.nl <fieldtrip-bounces@science.ru.nl> on behalf of Ling Wang <lingwang@m.scnu.edu.cn><br>
<b>Sent:</b> Wednesday, May 4, 2016 11:32 AM<br>
<b>To:</b> fieldtrip<br>
<b>Subject:</b> [FieldTrip] 4D-Neuroimaging Magnes 2500WH system</font>
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<div>Dear All,</div>
<div><br>
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<div>We recently started a joint study with the staff of a hospital specialized for brain diseases, where there is a
<span style="line-height:1.5">4D-Neuroimaging Magnes 2500WH system. We have collected a sample MEG data with the system to see if we can perform
</span>experiments<span style="line-height:1.5"> with the system. I am trying to analyze the data with FieldTrip. As introduced in the tutorial (http://www.fieldtriptoolbox.org/getting_started/bti), the software currently reads digital balancing weights only
for the Magnes 3600 system but not the </span>148-channel <span style="line-height:1.5">system. And yes, the software does not compute the balancing matrix for our MEG data, as indicated by the function, ft_read_header, "not applying digital weights in the
gradiometer balancing matrix", when reading our MEG data.</span></div>
<div><br>
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<div>I have three questions about analyzing these <span style="line-height:1.5">Magnes 2500WH </span><span style="line-height:1.5">MEG data with FieldTrip.</span></div>
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<div>1) Can we still carry out the analyses (ERF, TRF and connectivity) correctly at the sensory-level?<span style="line-height:1.5"> </span></div>
<div><span style="line-height:1.5">2) Is there a plan that FieldTrip would read the
</span><span style="line-height:1.5">digital balancing weights for</span><span style="line-height:1.5"> the MEG data of the
</span><span style="line-height:1.5">Magnes 2500WH</span><span style="line-height:1.5"> system?</span></div>
<div><span style="line-height:1.5">3) If we want to program to read the weights, what information do we need and possibly where can find the related information (e.g., the user manual of the system?)?</span></div>
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<div><span style="line-height:1.5">Thanks in advance.</span></div>
<div><span style="line-height:1.5"><br>
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<div><span style="line-height:1.5">Best wishes,</span></div>
<div><span style="line-height:1.5">Ling Wang</span></div>
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<div><span style="line-height:1.5">School of Psychology</span></div>
<div><span style="line-height:1.5">South China Normal University</span></div>
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