if acquisition is not continuous, it makes no sense to convolve with a HRF.
What I did to analyze an auditory fMRI study with discontinous acquisition (8
seconds delay between scans)was to set the stimuli as regressors instead as
conditions. The regressors were set to 1 o 0 according if haemodinamic
response to the stimuli was expected or not during each scan acquisition. It
Hope this helps
IDIBAPS-Hospital Clinic de Barcelona
University of Barcelona
Missatge de Susan Shuai <[log in to unmask]>:
> Dear Volkmar,
> My experiment is still a block design. Actually I have tried the methods both
> with and without slice timing. And the parameter setting is exactly what you
> suggested below. But the result is quite different from the original 2sec TR
> (continuous acquisition) analyzed result. For the original one, I got
> significant differences in contrasts I want. However, for the second
> experiment (cluster acquisition), both analysis methods did not show
> I am not sure whether it is because of the individual differences,
> hemodynamic changes caused by introducing TD or wrong analyzing procedure. I
> followed SPM manual, the first two examples' procedure in chapter "data sets"
> to do the analysis with my own parameters.
> Should I send you a more detailed SPMPrint file?
> Thank you and Best regards,
> Susan> Date: Mon, 24 Sep 2007 10:56:42 +0200> From:
> [log in to unmask]> Subject: Re: [SPM] Feel desperate in
> analyzing the discontinuous acquisition data> To: [log in to unmask]> > Dear
> Susan,> > your setup with silence periods between each scan is indeed tricky.
> If > your experiment can be modelled as a block design, I would go for> - no
> slice timing correction> - model TR as 3000 ms> - model blocks with onsets
> and duration> > If you really need to model the design event-related, then
> you should > enter TA as 1.55 secs and TR as 3.0 secs. For modelling, your TR
> would be > 3 seconds, and you have to set your reference time bin in a way
> that it > corresponds to the time when your reference slice was taken.> >
> hope this helps,> > Volkmar> > On Fri, 21 Sep 2007, Susan L. SHUAI wrote:> >
> > Dear SPMers,> >> > I am just a new comer to use SPM and doing fMRI
> experiment. I have> > encountered much difficulty in analyzing the data now.
> My experiment> > design is a !
> block design and the acquisition is a cluster acquisition> > because it will
> allow for silence to present auditory stimulus.> >> > Should I follow the
> Event-related analysis? In slice timing, what should I> > put as TA? Is it
> the start time of the last slice acquisition? For> > example, I have 32
> slices, and they are acquired in 1.6s. Is the TA 1.55?> >> > In the original
> experiment, I did the continuous acquisition and the TR is> > 2000ms. In the
> cluster acquisition, the TR is 3000ms and TD is 1400ms> > allowing for
> silence. But the analyzed results are very different. In the> > first case,
> most contrasts show significant differences, while in the> > second case,
> little contrasts show differences.> >> > I think the slice order and
> reference slice are all set right. What would> > be the reason for such large
> differences? How can I check my analyze> > result? I am feeling desperate
> about the situation now.> >> > Thank you for your help!!> >> > Regards,> >
> Susan> >> > -- > Vo!
> lkmar Glauche> -> Department of Neurology volkmar.glauche@uniklinik-fr
> eiburg.de> Universitaetsklinikum Freiburg Phone 49(0)761-270-5331> Breisacher
> Str. 64 Fax 49(0)761-270-5416> 79106 Freiburg
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