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<div class="" style="word-wrap:break-word; line-break:after-white-space">Dear Field-trip community,
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<div class="">I am working on EEG data from a motor learning task. in the first part of my analysis, I performed a time-frequency analysis (Morlet wavelet method) and cluster-based permutation test. I compared two different conditions (correct & incorrect movements)
within subjects and found a significant difference in the beta band (20-35 Hz) when subjects were provided with feedback. I attached the topographical plot from one subject that illustrates the difference between the conditions at the selected time point and
frequency (dif_morlet). As you can see, beta power was higher in one condition in lateral frontal electrodes.</div>
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<div class="">Now, I would like to better spatially locate the effect for this single subject. For this purpose, I followed the Beamformer tutorial on the website. In the first step, I selected the raw data of interest (at the time where the effect was seen)
and performed frequency analyses for the 20-35 Hz range (mtmfft, contrast between conditions shown in dif_mtmfft). There is an apparent difference between dif_morlet and dif_mtmfft and I am wondering why this is the case? One apparent reason is that the time-frequency
data were baseline corrected and the frequency data from mtmfft not.</div>
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<div class="">Using the power and CSD data from mtmfft, I performed the source analysis with a standard MRI and head model. The source was located in the left hemisphere (source plot), which is in stark contrast to the time-frequency data (dif_morlet). I am
aware that the source analysis is based on a lot of assumptions (conductivity etc.) that influence the calculations but it is very difficult to make sense of such discrepancy. </div>
<div class="">Maybe it is necessary to also baseline correct the mtmfft data before inputting them to the source analysis? Or doing the contrasting source localization betwee a single condition and the corresponding baseline data before contrasting the 2 conditions? </div>
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<div class="">I am providing all necessary files and scripts (TF_analysis & BEAMFORMER) if anyone is interested to reproduce the results that I am showing and reporting for this single subject (<a href="https://github.com/PatrickWiegel/EEG-Beamformer-Source-localisation" class="">https://github.com/PatrickWiegel/EEG-Beamformer-Source-localisation</a>). </div>
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<div class="">I would appreciate any help and discussion on that.</div>
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<div class="">All the best,</div>
<div class="">Patrick</div>
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<b class="">Patrick Wiegel</b><br class="">
<font color="#680823" class="">Department of Sport and Sport Science</font>
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University of Freiburg <br class="">
Sandfangweg 4<br class="">
79117 Freiburg i. Br . <br class="">
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<div class="">phone: +49 (0)761/ 203-4550<br class="">
<a href="mailto:patrick.wiegel@sport.uni-freiburg.de" class="">email: patrick.wiegel@sport.uni-freiburg.de</a><br class="">
web: www.sport.uni-freiburg.de</div>
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