{"id":392,"date":"2019-09-02T17:17:49","date_gmt":"2019-09-02T15:17:49","guid":{"rendered":"http:\/\/benediktehinger.de\/blog\/science\/?p=392"},"modified":"2019-09-02T17:18:10","modified_gmt":"2019-09-02T15:18:10","slug":"electrode-drift-in-eeg","status":"publish","type":"post","link":"https:\/\/benediktehinger.de\/blog\/science\/electrode-drift-in-eeg\/","title":{"rendered":"Electrode drift in EEG"},"content":{"rendered":"\n

I coudn’t find an image of electrode drift for my slides, so here I quickly generated one. The only fancy thing is the usage of datetime to have minutes on the x-axis (I also made this post so I don’t forget this trick ;))<\/p>\n\n\n\n

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DC-Amplifier (REFA-2, tmsi) plot of three electrodes over ~45min recording data. Strong DC-Offsets and drifts are observed (this is typical & normal)
<\/figcaption><\/figure><\/div>\n\n\n\n
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After filtering at 0.1Hz the strong drifts and offsets are gone (as intended), the y-axis has a very different axis now!<\/figcaption><\/figure><\/div>\n\n\n\n
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Obviously a cutoff-freq of 0.05Hz in the filter will still allow for some slow moving drifts. These offsets are usually accomodated for by baseline corrections<\/figcaption><\/figure><\/div>\n\n\n\n


Thanks to Anna Lisa Gert for this dataset<\/p>\n\n\n\n

% Load Data\nEEG = pop_loadeep_v4('subj23.cnt');\n% Load filtered data (takes 35min to filter...)\nEEG_filt = pop_loadset('2_subj23_lowpass_resample_deblank.set');\n%%\n% Convert time to actual time\ntimesnew = datetime(EEG.times\/1000,'ConvertFrom','epochtime','Epoch','2000-01-01');\n% select random channels\nchix = [5,63,27];\n\n% Plot the unfiltered data\nplot(timesnew,EEG.data(chix,:)')\n% Make the plot beautiful\ndatetick('x','MM','keeplimits','keepticks') % only show minutes\nxlabel('time [min]') \nylabel('voltage [\u00b5V]')\nlegend({EEG.chanlocs(chix).labels},'Location','East')\nbox off\ntitle('EEG Electrode Drift (DC Amplifier, avg ref)')\nset(gca,'fontsize', 14) % for a presentation\nset(gca, 'FontName', 'HelveticaNeueLT Pro 45 Lt')\n%%\n% Convert again because data have been resampled\ntimesnew = datetime(EEG_filt.times\/1000,'ConvertFrom','epochtime','Epoch','2000-01-01');\n\nplot(timesnew,EEG_filt.data(chix,:)')\n\ndatetick('x','MM','keeplimits','keepticks')\nxlabel('time [min]')\nylabel('voltage [\u00b5V]')\nlegend({EEG.chanlocs(chix).labels})\nbox off\ntitle('EEG Electrode Drift (avg ref, 0.1Hz filter)')\nset(gca,'fontsize', 14) % for a presentation\nset(gca, 'FontName', 'HelveticaNeueLT Pro 45 Lt')\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
I coudn’t find an image of electrode drift for my slides, so here I quickly generated one. The only fancy thing is the usage of datetime to have minutes on the x-axis (I also made this post so I don’t forget this trick ;)) Thanks to Anna Lisa Gert for this dataset<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-392","post","type-post","status-publish","format-standard","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/posts\/392","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/comments?post=392"}],"version-history":[{"count":0,"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/posts\/392\/revisions"}],"wp:attachment":[{"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/media?parent=392"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/categories?post=392"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/benediktehinger.de\/blog\/science\/wp-json\/wp\/v2\/tags?post=392"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}