How do different fMRI softwares handle events with a 0 second duration?

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This relates to an issue raised in nilearn.

Trying to figure out how different fMRI softwares will model events that have a 0 second duration.

SPM will include those in its design matrix. From memory I think those are included and given a duration equal to the time bin duration of the temporal resolution at which the convolution with HRF is done.

I have no knowledge of the internals of AFNI and FSL (or other tools that do fMRI analysis).

Does anyone know?

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For FSL, I think they treat 0-duration events as 0.05s (or at least they did way back in 2005). Here’s a post on their mailing list that might be helpful:

JISCMail - FSL Archive - Re: Event designs and co-linearity (JISCMail - FSL Archives)

Best wishes,
David

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Cool ! Thanks for the info.

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In AFNI, users specify the actual basis function. For an “instantaneous” event, I would expect one to use SPMG1 (or 2 or 3), GAM, or BLOCK with a short duration.

  • rick
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