Dear Torben,
Thanks for your very helpful suggestion!!
One thing not very clear for me is that I have read somewhere else a
design-related suggestion saying that 2 times SOAmax can be used as
cut-off, so for example in my case it is around 40-50.
I haven't yet done the phantom test but for this moment I have tried the
popular 100 cut-off.
The results with cutoff50 and cutoff100 look different, with cut-off 50
it looks much beter; so i just wonder why there exists such a
difference, and when the scanner-related cutoff and the design-related
cutoff are not close to each other, whether it is suitable to use a
design-related cutoff especially for efMRI which is not so efficient as
block or box-car design.
Best,
Qing
Torben Ellegaard Lund a écrit :
> Dear Qing
>
> In general I would use a phantom to find out what your scanner is like
> and what is the optimal cut-off.
>
> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind00&L=SPM&P=R111434&I=-3
> <http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind00&L=SPM&P=R111434&I=-3>
>
>
> Best
> Torben
>
> Torben Ellegaard Lund
> Assistant Professor, PhD
> The Danish National Research Foundation's Center for Functionally
> Integrative Neuroscience (CFIN)
> Aarhus University
> Aarhus University Hospital
> Building 30
> Noerrebrogade
> 8000 Aarhus C
> Denmark
> Phone: +4589494380
> Fax: +4589494400
> http://www.cfin.au.dk
> [log in to unmask] <mailto:[log in to unmask]>
>
>
> On 30/09/2007, at 2.06, Qing CAI wrote:
>
>> Dear SPMers,
>> I have a question on the high-pass filter.
>> In one of my tasks, I use a randomised event-related design with
>> stimuli type A,B, and C, each type 1/3.
>> SOAmin is 5-6 s (with random jitter).
>> The results with default high-pass filter (128) look a liitle noisy,
>> and I just wonder whether I can use a more strict cut-off, say 60. In
>> addition, a more general question is how the cut-off should be
>> decided in this case?
>> Thanks in advance.
>> Best,
>> Qing
>
>
--
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Qing CAI
Institut des sciences cognitives
67, boulevard Pinel
69675 Bron Cedex, France
Telephone: +33 (0)4 37 91 12 53
E-mail : [log in to unmask]
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