Dear SPM experts,
I have another question regarding parametric modulation of the trial
specific HRF in SPM5 and greatly appreciate any help.
For the 1st level analysis under fMRI model specification:
My design matrix contains 3 sessions, 4 trial types including null events
(HRF with spatial and temporal derivative)
and for each of the 3 trial types (not null events) I have defined several
modulating parameters.
One of the parameters is Reaction Time (in millseconds) for each stimulus
and trial.
Surprisingly after running the model (in bacth mode) and exploring the
design matrix before estimation (I redid this 3 times), the design matrix
would skip the Reaction Time parameter for some trials in some runs and
keep it for others.
Is there any reasonable explanation for this ?
Thanks for any help !!
Best,
Roland
Roland Zahn, Dr. med.
NIH / NINDS
Cognitive Neuroscience Section
Building 10, 5C206
10 Center Drive, MSC 1440
Bethesda, MD 20892-1440
Tel.: (+1)-301-402-6392
Fax.: (+1)-301-480-2909
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