Thanks Steve,
I read what I wrote below and I noticed that I worded it a little
ambiguously so I just
wanted to clarify:
1. the initial fixed effects analysis is run on the difference contrast COPE
image for POST-PRE. so essentially I am asking is there a group difference
among the difference of differences (active condition(post - pre) - placebo
(post - pre)).
2. Not sure how to design it all in one matrix so instead I am running the
lower level COPEs in seperate FEAT matrices, e.g.:
FEAT run 1: subj1 POST - subj1 PRE (run 2n times for n subjects)
FEAT run 2: ACTIVE difference COPE - PLACEBO difference cope for each
subject (run n times)
FEAT run 3: unpaired t test group difference of results of FEAT run 2. (run
once)
Thanks
Tal.
On Tue, 18 Aug 2009 08:34:11 +0200, Steve Smith <[log in to unmask]> wrote:
>Hi,
>
>Yes - that looks right.
>
>Cheers.
>
>
>On 17 Aug 2009, at 18:20, Tal Herbsman wrote:
>
>> I have the following experimental paradigm:
>>
>>
>> 1. patient and healthy control groups
>> 2. each subject has two separate scanning sessions on 2 days
>> 3. on each day subject has fMRI task followed by a)active substance
>> OR b)placebo
>> administration and repeat fMRI task
>>
>> I wanted to confirm proper design matrix construction to test the
>> question of whether
>> activation deltas (post - pre substance administration) differ among
>> group A and B
>>
>> My thought is to use a variation of the Multi-Session & Multi-
>> Subject (Repeated Measures
>> - Three Level Analysis) scenario on the FEAT webpage but instead of
>> running the initial
>> fixed effects analysis on subject mean COPEs, run it instead on
>> COPEs generated by a
>> fixed effect analysis of before and after condition for each subject.
>>
>> Not sure if this is correct or how to design the matrix. Any advice
>> would be much
>> appreciated.
>>
>> Tal.
>>
>
>
>---------------------------------------------------------------------------
>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)
>[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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