Dear Meera
say you model separately study / distractor / recognition; you know the
onsets but really you don't know the offsets - depending the subjects
you will have more or less long recognition periods for instance (the
same applies to study and distractor in fact) - so one thing to do could
be to model, at least for recognition, each trial with different
durations and also, to make sure your sampling of the hrf is efficient
to use a small jitter - it will ensure that different data points are
acquired specially because the model can vary trial-wise.
Cyril
> Hi SPM-ers,
>
> I have a slow ER design with a 1.5s fixation cross, 6s study trial (object presented in a certain location on screen), 3s distractor task, and 3.5s recognition task (where subjects are to indicate memory for the location of the item presented at the study phase) per trial for 42 trials. For a TR of 3s should I introduce jittering even if the length of the trial is not a multiple of the TR?
>
> Meera
>
>
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