<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Sebastian,<div><br></div><div>Biosemi isn't exactly reference-free, right? e.g the combination of CMS/DRL channel creates a reference, which is why electrodes close to that location have lower amplitude than ones more distant when viewed "raw" on montage setting in the acquisition software.</div><div><br></div><div>But the answer to your question - it doesn't really matter, I don't think. The way I understand it, a reference channel is needed on import to avoid losing the huge DC-offset potential in the signal, if it's there (I tend to use the BDF->EDF Converter program first, to drop file sizes and avoid using an aggressive 1hz filter against the BDF offset, which might smear ERPs). </div><div><br></div><div>So any channel will do. I tend to pick Pz because it's rather near the midpoint of the CMS/DRLs, and thus looks pretty close to the "raw" as I recorded it.</div><div><br></div><div>Best,</div><div>Andrew</div><div><br></div><div><br><div><div>On Sep 19, 2011, at 7:57 AM, seba wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear eeglab specialists,<div><br></div><div>I hope you can help me on this one:</div><div><br></div><div>I have recorded facial electromyography (EMG) with a Biosemi system, and want to analyze it in EEGLAB/matlab.</div><div>I am not sure about the question of the reference during importing.</div><div><br></div><div>I know that when first importing EEG data into EEGLAB, which was recorded reference-free with with a Biosemi system (<a href="http://www.biosemi.com/">www.biosemi.com</a>), one should indicate whatever channel as a reference, in order to improve the signal-to-noise ratio.</div><div><br></div><div>However, it is unclear to me what I should do when importing into EEGLAB EMG data recorded with the same system.</div><div>Should I indicate one electrode as a reference? And after having done so, should I rereference the data? to what?</div><div>Or is the EMG signal so strong that one can afford to keep some noise in the data and therefore does not need to indicate a reference during importing?</div><div>Would this also be true if I am interested in tiny EMG differences between conditions, as usual in facial mimicry paradigms?</div><div><br></div><div>Thank you very much for your help.</div><div><br></div><div>Best,</div><div>Sebastian</div><div><br></div><div><br></div><div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>----------------------------------------------------------------------</i></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>Sebastian Korb, Ph.D.</i></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>Swiss Center for Affective Sciences</i></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>University of Geneva, Switzerland</i></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>Tel.: +41223799812</i></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>Email: <a href="mailto:Sebastian.Korb@unige.ch">Sebastian.Korb@unige.ch</a></i></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><i>Webpage: </i></span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><a href="http://www.affective-sciences.org/user/34">http://www.affective-sciences.org/user/34</a></span></font></div><div><font class="Apple-style-span" size="3"><br></font></div><div><font class="Apple-style-span" size="3"><br></font></div><div><br></div></div></span></div></span></div></span></div></span></div></span></span><br class="Apple-interchange-newline">
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