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<p>Hello,<br>
<br>
this question is not really related to MNE itself, but maybe someone has seen something like this before (I am new to EEG analysis):<br>
<br>
I did a fast Fourier transform on 6 second long segments and calculated mean power values (averaged over electrodes, participants and 15 segments each). What perplexes me is the power peak at approx. 38 Hz:<br>
<br>
<img alt="" src="cid:jLbzOOjj-EIOGQ6rItFgzw1@webmail.uni-magdeburg.de" style="width: 400px; height: 320px;"><br>
<br>
My steps for data preparation were as follows:<br></p>
<ol>
<li>band-pass filter of data (1 to 45 Hz)</li>
<li>resampling from 512 Hz to 200 Hz</li>
<li>cut recording into consecutive segments of 6 sec duration</li>
<li>exclude segment if maximum allowed voltage step of 50 µV is exceeded</li>
<li>exclude segment if activity is lower than 0.5 µV</li>
<li>exclude segment if maximum and minimum amplitude exceed +/- 200 µV</li>
<li>exclude segment if maximum absolute difference of values in the segment > 200 µV</li>
<li>retain only segments that are ok for all electrodes</li>
<li>randomly choose 15 such good segments (all electrodes) from every participant</li>
<li>calculate FFT for every 2 sec time segment for every electrode and participant</li>
<li>calculate mean of all these FFTs</li>
<li>plot</li>
</ol>
<p>Has someone seen a similar peak before?<br>
<br>
Thanks for any help and advice.<br>
<br>
Nico</p>
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