Personally I am not a big fan of the 2*SOA*TR formula since it does
not work well for poorly designed paradigms. The high-pass filter is
applied to remove low frequency drift, which depends on your scanner
and not your paradigm (but I have already posted quite a bit on this).
In SPM8 (and maybe in SPM5) you can use the "Review" function to see
how much of your signal a given high-pass filter removes (see the
attached picture for a (toy) example with a 30s high-pass filter).
Den 20/07/2009 kl. 13.09 skrev Nico:
> Dear spm experts,
> i have a question concerning the high pass filter in spm5 in rapid
> or normal
> event related designs.
> I have read the following formula :2*SOA*TR to obtain the HPF
> cutoff. But
> this formula was always discussed (at least what i saw) in the
> presence of a
> block design.
> In my case i use a event related design with the following properties:
> Picturetype A = 3s
> ISI = random 3-5s
> Picturetype B = mean 6.5s (depending on the subjects response)
> ITI = random 5-7
> 1. Is the formula 2*SOA*TR also valid in cases of event or rapid event
> related designs?
> 2. If this is the case is my SOA in this study 4s (mean ISI) + 6s
> (mean ITI)
> = 10s -> HPF of 50s ?
> Or is the SOA only 4s because the SOA is defined as the "time interval
> between the onset of a first stimulus (A) and the onset of a second
> Thank you for any help you can offer!