<div dir="ltr"><div class="gmail_default" style="color:rgb(51,51,153)">Hello Malte, </div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)">To be extra cautious, as you intend, it is your best bet is to contact 5 to 10 authors who have worked with CHEPs previously and check in with them, and preferably some who work with the same CHEPs machine.</div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)">It would be good to make sure that you're not getting unexpected "electrical disturbances" from the connection between the EEG and CHEP station., by trying things out in various combinations. </div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)">Overall this might be something usual with CHEPs setup but you can't know for sure till you do appropriate survey and testing.</div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)">Best wishes.</div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)">If you get to some clarity about this situation, please share with the list so that other users can benefit from your experiences.</div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Nov 20, 2017 at 2:30 AM, Malte Anders <span dir="ltr"><<a href="mailto:malteanders@gmail.com" target="_blank">malteanders@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div><div><div><div><div><div><div>Dear EEG Lab list,<br><br></div>we are using a CHEPS thermode on a Medoc Main Station (<a href="https://medoc-web.com/products/pathway-model-cheps/" target="_blank">https://medoc-web.com/<wbr>products/pathway-model-cheps/</a>) and a 64 Channel g.HIamp from gtec with active electrodes (basically electrodes with an amplifier in it). I am currently measuring heat evoked potentials, so nothing really fancy.<br><br></div>When doing the eeg recordings, I am experiencing a strange behaviour I can't make heads and tails of. I am usually looking at an unreferenced EEG signal while recoding as we are doing and average referecing in the post-processing. Here is a screenshot of how the eeg looks _every_ time a trigger signal (CHEPS) of 51°C is applied to a subject (non-filtered, non referenced)<br><a href="https://imgur.com/ANxIPQb" target="_blank">https://imgur.com/ANxIPQb</a><br><br></div>Filtering the data doesn't make it better (notch, bandpass), just smoother, re-referencing (either average or earlobe, doesn't matter) completly removes the very significant pattern and results in a what I would call "normal" EEG.<br><br></div>I am especially worried about the very "flat sinus wave" after the trigger (trigger = peak temperature of 51 °C). When I measure an eeg without a subject and start the CHEPS electrode, no such pattern is seen. What I haven't tried is measuring and EEG on a subject, start the CHEPS measurement without the electrode applied to the subject to see if this pattern reoccurs, but I will try that. The only physical connection between EEG and CHEPS station is a +5V trigger cable which hopefully doesn't impose any electrical disturbances.<br><br></div>I just want to know if I need to be worried about the flat sinus wave after the trigger. I know that it is gone after the re-referencing, but I am not sure if there is any electrical interference I am currently not paying attention to. Also the pattern before the trigger always looks exactly the same (up, down, up, down and then flat sinus wave)!!! As I am looking for potentials in a 5-10 microvolt range I just want to be extra cautious, and the unreferenced signal produces this pattern in the millivolt-range, that's why I am a bit worried.<br><br></div>I am hoping this is the "normal" physical response of a subject in a heat evoked potential, but I just wanted to double check with somebody who has done evoked potentials before to rule out any interference here.<br><br></div>Thank you so much!<span class="HOEnZb"><font color="#888888"><br></font></span></div><span class="HOEnZb"><font color="#888888">Malte<br><div><div><div><div><br><br></div></div></div></div></font></span></div>
<br>______________________________<wbr>_________________<br>
Eeglablist page: <a href="http://sccn.ucsd.edu/eeglab/eeglabmail.html" rel="noreferrer" target="_blank">http://sccn.ucsd.edu/eeglab/<wbr>eeglabmail.html</a><br>
To unsubscribe, send an empty email to <a href="mailto:eeglablist-unsubscribe@sccn.ucsd.edu">eeglablist-unsubscribe@sccn.<wbr>ucsd.edu</a><br>
For digest mode, send an email with the subject "set digest mime" to <a href="mailto:eeglablist-request@sccn.ucsd.edu">eeglablist-request@sccn.ucsd.<wbr>edu</a><br></blockquote></div><br></div>