<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear FieldTrip list members,<div class=""><br class=""></div><div class="">I’ve got a question on the different methods available in ft_freqbaseline.</div><div class=""><br class=""></div><div class="">I have TFA data from an experiment where participants saw pictures and reacted to them. There is a pre-trial period (-1000 to 0 ms) during which the fixate a fixation cross and a trial period (0 to 1200 ms) during which they see the picture. I used mtmconvol in ft_freqstatistics to get the power. The frequencies are 4 to 20 Hz and I used 3 cycles (cfg.t_ftimwin = 3./cfg.foi). Then I want to baseline the data for plotting and analysis. As baseline period I chose -500 to -200 ms. (But using other baseline periods don’t change the picture.)</div><div class=""><br class=""></div><div class="">When I use an absolute baseline, the activity during the baseline period is around 0 and during the trial there are increases and decreases (i.e. positive and negative values). So this looks like one would expect.</div><div class=""><br class=""></div><div class="">When I use a dB baseline, however, the activity during the baseline period is not around 0, but rather around -1 to -2 dB. During the trial, I also get values around -1 to -3 dB. This is the command:</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Courier;" class="">cfg = [];</div><div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Courier; color: rgb(37, 153, 45);" class=""><span style="color: #000000" class="">cfg.baseline = [-0.5 -0.2]; </span>% baseline period = -500 to -200 ms, relative to stimulus onset</div><div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Courier;" class="">cfg.baselinetype = <span style="color: #b245f3" class="">'db'</span>;</div><div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Courier;" class="">cfg.parameter = <span style="color: #b245f3" class="">'powspctrm'</span>;</div><p style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Courier; min-height: 12px;" class=""> <br class="webkit-block-placeholder"></p><div style="margin: 0px; font-stretch: normal; font-size: 10px; line-height: normal; font-family: Courier;" class="">freq_data_baselined = ft_freqbaseline(cfg, freq_data);</div></div><div class=""><br class=""></div><div class="">What could be the reason for this discrepancy between absolute and dB baselines?</div><div class=""><br class=""></div><div class="">Thanks a lot for your help already in advance!</div><div class=""><br class=""></div><div class="">Regards,</div><div class="">Sebastian</div><div class=""><br class=""></div><div class=""><div class=""><div dir="auto" style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">-----------</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Dr. Sebastian Sauppe</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Department of Comparative Linguistics, University of Zurich</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Homepage: <a href="https://sites.google.com/site/sauppes/" class="">https://sites.google.com/site/sauppes/</a></div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Twitter: <a href="https://twitter.com/SebastianSauppe" class="">@SebastianSauppe</a></div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Google Scholar Citations: <a href="https://scholar.google.de/citations?user=wEtciKQAAAAJ" class="">https://scholar.google.de/citations?user=wEtciKQAAAAJ</a> </div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">ResearchGate: <a href="http://www.researchgate.net/profile/Sebastian_Sauppe" class="">http://www.researchgate.net/profile/Sebastian_Sauppe</a></div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">ORCID ID: <a href="http://orcid.org/0000-0001-8670-8197" class="">http://orcid.org/0000-0001-8670-8197</a></div></div>
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