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 differences.
 
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:
>
&! gt; > 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
> &! gt; second case, little contrasts show differences.
> >
&g t; > 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
> >
>
> --
> Volkmar Glauche
> -
> Department of Neurology [log in to unmask]
> Universitaetsklinikum Freiburg Phone 49(0)761-270-5331
> Breisacher Str. 64 Fax 49(0)761-270-5416
> 79106 Freiburg http://fbi.uniklinik-freiburg.de/

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