[Eeglablist] Stimulus design for SSVEP with flickering or reversing checkerboards

Tue Nov 4 12:10:21 PST 2014

<div id='yahoo__compose_area' style="background-color:white; display:block; font-family:HelveticaNeue-Regular,Helvetica; font-size:15px;"><div>Yes, I think it should be 5 Hz. For pattern reversal VEP according to ISCEV 2010 standard they are using 2 reversal per second equal to 1 Hz (black turn to be white and back again to black in one second) so it's considered to make one complete cycle per second.</div><div><br></div><div><br></div><div>AHMED</div></div><div id='yahoo__original_message' class='yQTDBase'><br><blockquote style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex; ">At 5 Nov 2014 3:36:27 am, Makoto Miyakoshi<'<a href="mailto:mmiyakoshi at ucsd.edu" x-apple-data-detectors="true" x-apple-data-detectors-type="link" x-apple-data-detectors-result="1">mmiyakoshi at ucsd.edu</a>'> wrote:<div dir="ltr">Dear Masaki,<div><br clear="none"></div><div>Your comment is welcome!</div><div><br clear="none"></div><div>Makoto</div></div><div
 class="gmail_extra"><br clear="none"><div class="yQTDBase yqt8847331288" id="yqtfd01829"><div class="gmail_quote">On Tue, Oct 28, 2014 at 10:04 PM, Dr.Rohit Tyagi <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:rohittyagi_2k at rediffmail.com" target="_blank" href="javascript:return">rohittyagi_2k at rediffmail.com</a>></span> wrote:<br clear="none"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Hi Everyone,<br clear="none"><br/><br clear="none"><br/>I have a very simple question, because of a confusion raised by a colleague. We are studying the frequency spectral density characteristics of SSVEP EEG data. The stimuli that we use are a pair of complimentary black-white checkerboards, which are shown alternately at a frequency of 10 Hz to induce SSVEP on an LCD screen.<br clear="none"><br/>One checkerboard (pic1) is shown for 100ms, followed by its inverse (pic2) for 100ms and so on for
 the whole trial duration of about 30-40 seconds.<br clear="none"><br/>Here is where a difference of opinion has cropped up - <br clear="none"><br/>My colleague says that since I am presenting pic1 only 5 times in this one second, so the frequency of stimulation is not 10Hz but 5 Hz. I believe that what matters in such a paradigm is the frequency of reversal which will drive the brain, so the effective frequency is 10 Hz.<br clear="none"><br/>Using spectopo function, I can plot the frequency characteristics of the EEG data and it can show a clear peak at 10 Hz using this stimulation, however I wanted to confirm whether my understanding of generating SSVEP with reversing checkerboard is correct.<br clear="none"><br/>On a second issue, say I was using just one checkerboard (pic1) and did an onset/offset stimulation - where the checkerboard appears on the LCD (with gray background) for say 50ms, then disappears for 50ms and so on - in this case I can
 present the same picture for 10 times in a second, but I suspect that the offset also counts as a "stimulation" event and thus the spectral response might show a peak at 20 Hz.<br clear="none"><br/><br clear="none"><br/>Any clarifications would be very helpful.<br clear="none"><br/>Thanks and Regards,<br clear="none"><br/>Rohit<br clear="none"><br/><br clear="none"><table border="0" width="100%" height="57" cellspacing="0" cellpadding="0" style="font-family:Verdana;font-size:11px;line-height:15px;"><tbody><tr><td colspan="1" rowspan="1"><a rel="nofollow" shape="rect" target="_blank" href="http://sigads.rediff.com/RealMedia/ads/click_nx.ads/www.rediffmail.com/signatureline.htm@Middle?"><img src="http://sigads.rediff.com/RealMedia/ads/adstream_nx.ads/www.rediffmail.com/signatureline.htm@Middle"></a></td></tr></tbody></table><table cellpadding="0" cellspacing="0"><tbody><tr><td colspan="1" rowspan="1"><div style="font-family:Arial, Helvetica,
 sans-serif;font-size:14px;">Get your own <span style="padding-bottom:0px;background-color:#cc0000;padding-left:3px;padding-RIGHT:3px;font-family:Arial, Helvetica, sans-serif;color:#ffffff;font-size:12px;padding-top:0px;"><b>FREE</b></span> website,  <span style="padding-bottom:0px;background-color:#c00;padding-left:3px;padding-RIGHT:3px;font-family:Arial, Helvetica, sans-serif;color:#ffffff;font-size:12px;padding-top:0px;"><b>FREE</b></span> domain & <span style="padding-bottom:0px;background-color:#c00;padding-left:3px;padding-RIGHT:3px;font-family:Arial, Helvetica, sans-serif;color:#ffffff;font-size:12px;padding-top:0px;"><b>FREE</b></span> mobile app with Company email.  </div></td><td colspan="1" rowspan="1"><a rel="nofollow" shape="rect" target="_blank" href="http://track.rediff.com/click?url=___http://businessemail.rediff.com/email-ids-for-companies-with-less-than-50-employees?sc_cid=sign-1-10-13___&cmp=host&lnk=sign-1-10-13&nsrv1=host"
 style="font-family:Arial, Helvetica, sans-serif;color:#fff;font-size:14px;color:#0000cc;"><b>Know More ></b></a></td></tr></tbody></table><br clear="none">_______________________________________________<br clear="none"><br/>Eeglablist page: <a rel="nofollow" shape="rect" target="_blank" href="http://sccn.ucsd.edu/eeglab/eeglabmail.html">http://sccn.ucsd.edu/eeglab/eeglabmail.html</a><br clear="none"><br/>To unsubscribe, send an empty email to <a rel="nofollow" shape="rect" ymailto="mailto:eeglablist-unsubscribe at sccn.ucsd.edu" target="_blank" href="javascript:return">eeglablist-unsubscribe at sccn.ucsd.edu</a><br clear="none"><br/>For digest mode, send an email with the subject "set digest mime" to <a rel="nofollow" shape="rect" ymailto="mailto:eeglablist-request at sccn.ucsd.edu" target="_blank" href="javascript:return">eeglablist-request at sccn.ucsd.edu</a><br clear="none"></blockquote></div></div><br clear="none"><br clear="all"><div><br clear="none"></div>--
 <br clear="none"><div class="gmail_signature"><div dir="ltr">Makoto Miyakoshi<br clear="none">Swartz Center for Computational Neuroscience<br clear="none">Institute for Neural Computation, University of California San Diego<div class="yQTDBase yqt8847331288" id="yqtfd67867"><br clear="none"></div></div></div><div class="yQTDBase yqt8847331288" id="yqtfd97945"><br/></div></div><div></div></blockquote></div>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20141104/388d637b/attachment.html>