<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:10pt"><span><div class="yiv115705295im"><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">Dear all,</span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"><br></span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"><br></span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">I was wondering, whether anybody has experience in / ideas about baseline corrections concerning response-locked ERPs.</span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"> </span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">We are primarily interested in processes happening directly before participants come to a decison, i.e. press a key. <br><var id="yui-ie-cursor"></var></span></div><div><span style="font-family: arial,
helvetica, sans-serif; font-size: 13px;">Our experimental setup was the following: After a </span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"></span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">fixation cross, a prime word (positve/negative) was presented for 300 ms, followed by a target, where subjects had to make a binary decision and indicate it by keypress. </span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">Participants responded without having any time restrictions. The a</span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">veraged Response Times varied from 1200-3000 ms.</span></div><div><div class="yiv115705295im"><div><font face="arial, helvetica, sans-serif"><span style="font-size: 13px;"><br></span></font><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">Having these varying RTs, 3 possibilities come to my
mind, how to set the baselines, when epoching the data:</span></div></div><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"><br></span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">1) Using the 500ms before target presentation or prime as baseline.</span></div><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"></span></div><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">2) Determining a baseline relative to response e.g. 1500 ms to 1000 ms before button press. This would raise the problem, that the baseline varies between trials, it can be either post- or pre-target, or even on the target.</span></div><div class="yiv115705295im"><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"></span></div><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">3) </span><span style="font-family: arial,
helvetica, sans-serif; font-size: 13px;">Using the average voltage of the whole epoch and subtracting it from the epoch data, as proposed by Steven Luck in his book (2005).</span><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"> </span></div><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;"></span></div></div><div class="yiv115705295im"><div><span style="font-family: arial, helvetica, sans-serif; font-size: 13px;">It would be nice if you have some opinion or an idea how to deal with the problem.<br><br>Best<br><br>Elise<var id="yiv115705295yui-ie-cursor"></var></span></div></div></div></span></div></body></html>