Hi Jeanette,
Thank you very much!
I think I set the analysis up correctly (see the design attached) but
the results does not look like the difference in activation between
the to first-level results (which I guess it should?).
Am I doing something wrong?
Best,
Anders
2013/3/27 Jeanette Mumford <[log in to unmask]>:
> Hi,
>
> Calculate the paired differences in a within-subject, fixed effects second
> level model. Design matrix
> 1 0
> 0 1
> contrast
> 1 -1
>
> Repeat for all subjects and you have a single paired difference for each
> subject that you can enter into your group model. The group model will
> include a column of 1s and age (mean centered).
>
> Cheers,
> Jeanette
>
>
> On Wed, Mar 27, 2013 at 10:14 AM, Anders Hougaard <[log in to unmask]>
> wrote:
>>
>> Dear FSL experts,
>>
>>
>> Consider this experiment:
>>
>> A group of subjects is scanned during some kind of stimulation before
>> (condition A) and after (condition B) some kind of intervention.
>>
>> I want to know if there is a difference in the activation caused by
>> the stimulation between condition A and condition B.
>> For fMRI data this is easily set up in a paired design using FLAME.
>>
>> The next thing I want to know if a subject's age has an effect on how
>> much the activation changes from condition A to B.
>> Putting subject age into the design as a covariate would cause the
>> design matrix to become rank deficient and generally would not make
>> sense since we are looking at within-subject differences and all
>> subjects have the same age before and after the intervention.
>>
>> How can I find out about the effect of age, or any other
>> subject-specific parameter such as gender or handedness, in this case?
>>
>>
>> All the best,
>>
>> Anders
>
>
|