When I'm reading the documentation of importing events in EEGLAB from a file here I have noticed that when we used a stimulus , we must know which time we will apply it , since in the dataset file , you have to identify of what times stimulus happen .
I don't know if my understanding is right or not , since i didn't deal with EEG data practically (but in 2 weeks I will), but I was reading a theoretical topics and papers on that.
thanks in advance.
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$\begingroup$ I'm unclear what this question means; it sounds to me like you're asking for theoretical papers on why you have to imported events have to have a timestamp, is that right? $\endgroup$ – Krysta Oct 23 '14 at 15:22
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$\begingroup$ @Krysta, my question is : when we do an ERP experiment do we need to know what times or period of times that stimulus begin ?(i hope that's clear) $\endgroup$ – Learner Oct 23 '14 at 15:45
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If I understand your question correctly, yes, since ERP involves averaging over similar events, very accurate time-locking to stimulus onset is critical. The idea of an ERP is that activity relevant to the stimulus will happen at a similar timepoint after similar stimuli--if you don't have an accurate time stamp (usually to the level of single milliseconds if not better), then the activity will be "smeared" across the time course. For a good overview of ERPs, see the article Event-related Potentials: An Overview
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$\begingroup$ then we cannot know if a part of EEG signal is a P300 stimulus without knowing the stimulus onset , which means that we know that part is a P300 signal from the time line , not from it's features , for example if the stimulus onset at t=1 s , them at t=1.3 s we expect a P300 signal , is this right ? $\endgroup$ – Learner Oct 24 '14 at 3:57
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3$\begingroup$ Basically yes, although the P3 best correlates with response timing, not stimulus timing, and there exist algorithms for identifying P3s based on the data, although not very well. $\endgroup$ – jona Oct 24 '14 at 9:11
