Does the duration of the epoch of interest in fMRI need to be a multiple of TR?

1

Hi all,

I am designing an fMRI experiment whereby, for each trial, subjects need to listen to an auditory stimulus (of arbitrary duration), and subsequently give a rating for each stimulus.

I intend to compare the BOLD signal for the different conditions under which that stimulus is presented. Thus, the part (epoch) of the trial that is of interest for analyses (contrasts) is when the stimulus is presented.

Is there any reason (to do perhaps with MR physics or statistical analyses) whereby the duration of the epoch of interest (i.e. of the auditory stimuli) should be an integer multiple of the TR, or can this really be arbitrary?

Thanks for any replies!

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Is there any reason (to do perhaps with MR physics or statistical analyses) whereby the duration of the epoch of interest (i.e. of the auditory stimuli) should be an integer multiple of the TR, or can this really be arbitrary?

Just to be sure I’m understanding, I’m interpreting this question to mean “If I model an event or block of events, do the event boundaries need to coincide with volume acquisition onsets/offsets?”

If that’s a decent rephrasing, then the answer is no, modeled events can be of any onset and duration.

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That is indeed what I meant, and thank you very much for clarifying!