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<body text="#000000" bgcolor="#FFFFFF"><p><span style="padding: 3px 10px; border-radius: 5px; color: #ffffff; font-weight: bold; display: inline-block; background-color: #ff0000;"> External Email - Use Caution </span></p><p></p>
<p>hi,</p>
<p>i faced a similar question some time ago. there is one thing to
keep in mind when doing (time)frequency transforms on source data:</p>
<p>when data is projected to source space, it is projected to three
components per source: one for each spatial dimension. these three
components are then normally combined by taking the norm. this
step includes squaring the data, so all samples that were negative
are now positive. this is mostly ok when staying in the
time-domain (although one must be aware of it, but it will not
mess up anything). however, it essentially doubles the frequencies
of all oscillations in your data, so it is highly problematic for
(time)frequency transforms.</p>
<p>mne python provides a few ways to avoid this problem:</p>
<ol>
<li>use source_induced_power. this function calculates the TFR for
all three components of every source and combines the power
values afterwards.</li>
<li>restrict the amount of spatial components per source to 1 when
setting up the source model. i do not know if that is possible
in mne python.</li>
<li>restrict apply_inverse to return only one component.
pick_ori='normal' would work well for EEG but not for MEG,
though because it is mostly sensitive to the two tangential
components.</li>
<li>set pick_ori to 'vector' which should return all three spatial
components per source, apply whatever algorithm(s) you need and
combine them later yourself.</li>
</ol>
<p>i hope, this is all correct. if not, please correct me!</p>
<p>cheers,<br>
thomas<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">Am 11.10.18 um 15:04 schrieb Sheraz
Khan, PhD:<br>
</div>
<blockquote type="cite"
cite="mid:52257.73.167.230.81.1539263094.squirrel@mail.nmr.mgh.harvard.edu">
<pre class="moz-quote-pre" wrap="">Yes, in addition, once you extract the source space data from the label,
you can also use tfr_multitaper on the label time series.
HTH
Sheraz
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<blockquote type="cite">
<pre class="moz-quote-pre" wrap=""> External Email - Use Caution
You mean basically using source_induced_power instead o tfr_multitaper?
Thanks for answering,
Karin
Den tors 11 okt. 2018 kl 00:55 skrev Sheraz Khan, PhD <
<a class="moz-txt-link-abbreviated" href="mailto:sheraz@nmr.mgh.harvard.edu">sheraz@nmr.mgh.harvard.edu</a>>:
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<pre class="moz-quote-pre" wrap="">Hi Karin,
Yes, you need to pick few labels in the source space to estimate ERS/ESD
on it.
Please look at the following example:
<a class="moz-txt-link-freetext" href="https://martinos.org/mne/stable/auto_examples/time_frequency/plot_source_label_time_frequency.html">https://martinos.org/mne/stable/auto_examples/time_frequency/plot_source_label_time_frequency.html</a>
Thanks
Sheraz
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<blockquote type="cite">
<pre class="moz-quote-pre" wrap=""> External Email - Use Caution
Hi!
Is it possible to compute ERS/ERD maps based on source space instead
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">of
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">sensor space?
Best,
Karin
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<pre class="moz-quote-pre" wrap="">
-------------------------
Sheraz Khan, M.Eng, Ph.D.
Instructor in Radiology
Athinoula A. Martinos Center for Biomedical Imaging
Massachusetts General Hospital
Harvard Medical School
McGovern Institute for Brain Research
Massachusetts Institute of Technology
Tel: +1 617-643-5634
Fax: +1 617-948-5966
Email: <a class="moz-txt-link-abbreviated" href="mailto:sheraz@nmr.mgh.harvard.edu">sheraz@nmr.mgh.harvard.edu</a>
<a class="moz-txt-link-abbreviated" href="mailto:sheraz@mit.edu">sheraz@mit.edu</a>
Web: <a class="moz-txt-link-freetext" href="http://sheraz.mit.edu">http://sheraz.mit.edu</a>
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<pre class="moz-quote-pre" wrap="">
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
-------------------------
Sheraz Khan, M.Eng, Ph.D.
Instructor in Radiology
Athinoula A. Martinos Center for Biomedical Imaging
Massachusetts General Hospital
Harvard Medical School
McGovern Institute for Brain Research
Massachusetts Institute of Technology
Tel: +1 617-643-5634
Fax: +1 617-948-5966
Email: <a class="moz-txt-link-abbreviated" href="mailto:sheraz@nmr.mgh.harvard.edu">sheraz@nmr.mgh.harvard.edu</a>
<a class="moz-txt-link-abbreviated" href="mailto:sheraz@mit.edu">sheraz@mit.edu</a>
Web: <a class="moz-txt-link-freetext" href="http://sheraz.mit.edu">http://sheraz.mit.edu</a>
_______________________________________________
Mne_analysis mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Mne_analysis@nmr.mgh.harvard.edu">Mne_analysis@nmr.mgh.harvard.edu</a>
<a class="moz-txt-link-freetext" href="https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis">https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis</a>
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<pre class="moz-signature" cols="72">--
Dr. Thomas Hartmann
Centre for Cognitive Neuroscience
FB Psychologie
Universität Salzburg
Hellbrunnerstraße 34/II
5020 Salzburg
Tel: +43 662 8044 5109
Email: <a class="moz-txt-link-abbreviated" href="mailto:thomas.hartmann@th-ht.de">thomas.hartmann@th-ht.de</a>
"I am a brain, Watson. The rest of me is a mere appendix. " (Arthur Conan Doyle)
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