Hi Andrew
There is no reason that the microtime specification should cause this error.
You could stick with 16 and 1 or choose 30 if you want to break up the TR
into the same number of bins as your slices. I don't think it matters that
much in general. It would make sense to choose an onset that is temporally
in line with any slice timing correction. If you align your slice time onset
to the first slice in time stick with 1, to the middle slice in time then 8
or 9, etc. However, none of this should create or fix the error you are
getting. The cause is likely that you are including a regressor with 0
onsets. In fact the error says that your design has 0 columns (
size(X)=[1,0] ). Line 17 of spm_orth is: X = X(:,any(X)); This is before
any actual orthogonalization is occurring. Basically it says keep only
columns that contain at least 1 non-zero value. So if
X = 1 0 0
1 1 0
0 1 0
then any(X) = [1 1 0] and X = X(:,any(X)) is
X = 1 0
1 1
0 1
if X = 0 0 0 then X = X(:,any(X)) is an empty matrix: 1-by-0
So the onsets for your events have somehow gone missing.
darren
> -----Original Message-----
> From: SPM (Statistical Parametric Mapping)
> [mailto:[log in to unmask]] On Behalf Of Andrew Park
> Sent: Thursday, November 29, 2007 3:11 PM
> To: [log in to unmask]
> Subject: [SPM] SPM5 Microtime parameter help
>
> Hello
>
> I am having trouble with running the fMRI model spec. My
> supervisor suggests that there is a problem with our
> Microtime Resolution (=16) and Microtime Onset (=1), which
> are the default values.
> What values would be wise to enter if we have a 2 second TR,
> 30 slices with 90 repetitions aquired via interleave? I have
> played around with different values , with no success so we
> just went with the default. Would this affect the error we
> get with spm_orth.m?
>
> Thanks so much,
> Andrew
>
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