Dear Batiah,
you have to be careful here. FIR is an onset-related model, where I guess only duration=0 makes sense.
The length of the modelled response and the granularity is determined by "order" and "length", where the granularity/resolution is length ./ order. Note that the resolution
cannot be infinitely high, because you then might end up with empty regressors due to sampling. Usually people define the granularity as a TR i.e. order=10, then length = 10*TR gives you 10 bins after stimulus onset with a resolution of one TR per bin. PS. The units depend on whether you specify everything in seconds or scans (...fmri_spec.timing.units).
I hope this helps,
Christian
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Prof. Dr. Christian Büchel
Institut für Systemische Neurowissenschaften Haus W34, Universitätsklinikum Hamburg-Eppendorf Martinistr. 52, D-20246 Hamburg, Germany
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> -----Ursprüngliche Nachricht-----
> Von: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] Im
> Auftrag von Batiah Keissar
> Gesendet: Montag, 11. März 2024 09:12
> An: [log in to unmask]
> Betreff: [EXT] [SPM] Finite Impulse Response and event durations in SPM
>
> Hello SPM experts,
>
> I am using Finite Impulse Response in an SPM fMRI analysis, and I wanted to
> ask if it is possible to do this with a window containing events with durations of
> 0 seconds? What would be the implications for my analysis in comparison to
> longer durations?
> Also, If anyone has recommendations for further learning materials on this
> topic I would greatly appreciate it.
>
> Thank you all kindly,
>
> Batiah
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