People try to set this to be at least 2 times the longest interval between event onsets or just leave it at 128. For designs with rare events, this can be problematic, but detecting events could also be problematic too. In block designs, you will want it to be at least 2 times the onset of block A to the onset of block A. So if you have a design of 30s off, 30s A, 30s off, 30s B, 30s off, 30s A., then you would want to use at least 180s.
If your doing a standard event-related design, 128 should be sufficient.
Best Regards, Donald McLaren ================= D.G. McLaren, Ph.D. Postdoctoral Research Fellow, GRECC, Bedford VA
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On Mon, Jan 16, 2012 at 2:29 PM, adams adams <[log in to unmask]> wrote:
Hi, By defalut , SPM set Haemodynamic Response Function equal to 128 , how can i check if this valueif its suitable to my design
