BIDS events.tsv duration/onset_time for event-related fMRI


I am in the process of converting my dataset to BIDS. The final step I have is to create an “events.tsv” file for my task-based files before taking the data to fMRIprep. I am wondering if the “events.tsv” file is used in fMRIprep and if it will need to be used in contrasts/ how specific this file must be? Or, is it mostly used as metadata for the future?

One of our tasks is an event-related fMRI paradigm. The stimulus duration is not always the same and fluctuates based on participant reaction time. What can I put in for ‘duration’? Also, we have built in null trials (black screen with fixation cross) that also fluctuate in duration based off of the reaction time of the previous trial. Should I put these onset times in the “events.tsv” file too?

Finally, is it most common to create a .tsv file and use it as a template in a higher level BIDS folder, or do people have their stimulus presentation programs (i.e. E-prime, Presentation) output BIDS compatible “events.tsv” files for each run? I am torn between the two options.

Thank you for the help,

It is not used in fmriprep, but in higher level modelling tools such as fitlins.

I would put the actual duration of the stimulus (even if variable).

Does not hurt to add those!

It seems that you will need individual events files for each run since you require variable durations for events.

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Thanks @ChrisGorgolewski for detailed answers… very helpful.