I have been tasked with epoching EEG data and then I need to re-align the epoched data so that all the EEG is aligned to the target event. The researcher I'm working with called this the re-align function.
For context, we will be using an SVM algorithm on event related potentials after the data is preprocessed and epoched. The eeg data we have has event markers for the beginning of a trial and also for when the participant responds to a stimulus. There are many of these trials back to back in a continuous .raw eeg file. I need to create an epoch for each trial and then re-align each epoch with the event marker for the response for the that trial.
I've looked for a re-align function in the documentation but didn't see anything. Is there another name for the process that I want to do? Any advice on completing this process?
Thank you in advance.
Hello,
I recommend you to read the " Get started" tutorials.
You may find answers to your questions on the Tutorial7 and Tutorial15
Once you have your data within brainstorm you can import and process your data according to any events.
Hi tmedani, thanks for the reply. The tutorials are what I was referring to as the documentation. I've been through the tutorials that seem relevant, including Tutorial 7 and 15, but I didn't find what I was looking for.
I'm just wondering if it's even possible to do this with Brainstorm or if I will need to find another way to do it using different technology. I am hoping someone with experience with this process could provide advice.
The process that you describe is a common approach, and you can do it within Brainstorm. You need to import first your data to Brainstorm.
Once you have your data marked with the events, you can import all the epochs labeled with the same events, and then you can compute your ERPs.
That is good to hear! I have the data imported in Brainstorm and all of the relevant events are already marked. I've learned how to import the epochs around these events through the tutorials but it seemed like there was another process involved for re-aligning the epochs to the event markers after the epochs are created. Does this seem wrong? Is the epoching of the data based on the markers the only thing needed for ERP before averaging or is there another process to re-align the data after the epochs are created?
I'm not sure I understand what you expect from this "re-align process", beyond setting t=0 at each event of interest, with some time before and some time after.
In terms of Brainstorm pipeline, this would be a single step: no need to first cut by trials and then by events. Just link the continuous file to the database (menu Review raw file), then epoch based on the event markers. Just make sure that there is no overlap between multiple trials in the time windows you select.
If there is something that we did not understand correctly, please post screen captures illustrating your question.
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