HI
Thanks a lot for reply. I do have another related question. When I
tried a window of 14 seconds, the hemodynamic functions of 4 EVs look
physiologically plausible. However, when I tried a window of 12
seconds, the hemodynamic functions of 3 EVs did not look right (the one
EV looked a little better than others). I wasn't sure whether the FIR
impulse is sensitive to the window length. Is this because I didn't
have enough time window to cover the hemodynamic rise and fall time?
Thanks,
Junghee
On May 5, 2007, at 12:10 AM, Steve Smith wrote:
> The window length is divided by the number of FIR impulses that you
> ask for so that each impulse has duration length/number seconds.
> A common approach is to organise that so that the length covers the
> normal haemodynamic rise and fall time (eg 15 seconds) and set the
> number so that each is one TR in duration.
> Cheers.
>
>
> On 4 May 2007, at 23:16, Junghee Lee wrote:
>
>> Hello Everyone,
>> I have a question of using FIR basis function. We used a fast
>> event-related design (TR=2) and there are 4 EVs. I would like to
>> compare a window of 12 seconds and a window of 14 seconds.
>>
>> I'm not sure whether I understand what "number" means exactly. Is
>> this number of FIR basis functions? If so, is there any optimal
>> number of functions I should use?
>>
>> Thanks a lot!
>> Junghee
>
>
> -----------------------------------------------------------------------
> ----
> Stephen M. Smith, Professor of Biomedical Engineering
> Associate Director, Oxford University FMRIB Centre
>
> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
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>
------------------------------------
Junghee Lee
Post-doctoral fellow
Semel Institute of Neuroscience and Hunan Behavior, UCLA
Phone: 310-478-3711 ext.42986
email:[log in to unmask]
Mail: UCLA/VA Greater Los Angeles Healthcare System
11301 Wilshire Blvd.
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Los Angeles, CA 90073
Web:http://greenlab.npih.ucla.edu or
http://www.psy.vanderbilt.edu/students/leej11
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