Steve,
In a recent posting, Russ recommended modeling the Go response rather
than leaving it out as an implicit baseline. What do you think?
I'll try 30s, though the recent postings didn't do much to help me
understand why. My understanding is that the highpass should be
around the "total cycle time," which would be about 9s. I see where
you suggest 10-30s, so we should up ours a bit. But I unclear why I
would push it up to 30s rather than 10s.
Bryon
On Aug 19, 2005, at 5:43 AM, Stephen Smith wrote:
> Hi Bryon,
>
> This looks fine I think. I would probably raise the highpass to
> maybe 30s
> - though of course it's hard to quantitate this (see recent postings).
>
> Cheers, Steve.
>
>
> On Wed, 17 Aug 2005, Bryon Adinoff wrote:
>
>
>>>
>>>
>>> This is my first analysis with FSL, and would appreciate input on
>>> our model setup.
>>>
>>> We are analyzing the results of a stop signal task (SST) (from
>>> Rubia et al.).
>>>
>>> There are 196 volumes, TR 1.8. During each TR the subject
>>> 1. responds to a stimulus with either a left or right button press
>>> (GO response, 156 trials)
>>> 2. is signaled to withhold a response but does not inhibit (NoStop
>>> response, about 20 trials)
>>> 3. is signaled to withhold a response and is successful in doing
>>> so (Stop response, about 20 trials)
>>> Each NoStop or Stop response is separated by 4-6 Go responses.
>>>
>>> If the subject responds prematurely or with the wrong button, the
>>> response is discarded. In addition, 10 extra volumes at the end
>>> are discarded.
>>>
>>> I am using a highpass filter of 9 sec.
>>>
>>> I am using the GO response as the baseline, so is not included as
>>> an EV.
>>>
>>> EV1 is NoStop
>>> EV2 is Stop
>>> EV3 is Discard
>>>
>>> I have attached the three textfiles (3 column entries) used to
>>> describe these 3 EVs.
>>>
>>> Three contrasts are assessed:
>>> NoStop 1 0 0
>>> Stop 0 1 0
>>> NoStop - Stop 1 -1 0
>>>
>>> Thanks.
>>>
>>> Bryon
>>>
>
> --
> Stephen M. Smith DPhil
> Associate Director, FMRIB and Analysis Research Coordinator
>
> Oxford University Centre for Functional MRI of the Brain
> John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
>
> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
>
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