Dear Jerry,
> SPM99 will accept fractional scans in the vector of onsets (e.g. 0.8 2.3 4.2 ...).
> When using an impulse type stimulus, if the stimuli are not in synchrony with the epi
> scans, should the actual onset times be expressed in fractional scans?
>
> Perhaps SPM99 accepts non-integer data and then rounds the data to the closest integer.
In SPM99, there is a variable named fMRI_T, which represents the number
of bins per TR used for discretizing the vector of onsets. The default
value is 16, i.e. with a TR of e.g 4.0 seconds you would have 0.25
second bins.
It is a user defined value, you can change fMRI_T in spm_defaults under
fMRI statistics.
Stefan
--
Stefan Kiebel
Functional Imaging Laboratory
Wellcome Dept. of Cognitive Neurology
12 Queen Square
WC1N 3BG London, UK
Tel.: +44-(0)20-7833-7478
FAX : -7813-1420
email: [log in to unmask]
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