Thanks for your feedback Liam. Here is what I was also considering: The
patients show a wide range of benefit from our treatment. To understand what
areas predict outcome, I was planning to do a t-test for each individual
first ((Session 1 + Session 2) - (Session 3 + Session 4)) using a fixed
effect comparison. Then, in the next level analysis, to input the resulting
COPEs to predict group outcome (e.g. greater signal change = greater
recovery) using mixed effects. That is, are there specific areas that show
greater signal change in those patients that show greater recovery? Again,
hope this makes sense. -
Julius
The way I understand your analysis is as follows:
21 subjects in the before treatment condition
(same) 21 subjects in the after treatment condition
You want to compare the two conditions - this you do with a paired t-test
within a Mixed effects analysis
Say you have two runs for each condition? You would average across these
runs using a Fixed effects analysis before using the COPE files of the Fixed
effects analysis to do the Mixed effects paired t-test.
Hope this makes sense.
Liam.
*******************************************
Liam Nestor, Ph.D
Office C8-523
Laboratory for Molecular Neuroimaging
Semel Institute for Neuroscience and Human Behavior
760 Westwood Plaza
Los Angeles 90024
Tel: 310-206-0655
E-mail: [log in to unmask]
*******************************************
________________________________________
From: FSL - FMRIB's Software Library [[log in to unmask]] On Behalf Of
Julius Fridriksson [[log in to unmask]]
Sent: Friday, August 28, 2009 12:59 PM
To: [log in to unmask]
Subject: [FSL] higher level FEAT
Hi - I have a group of 21 patients who underwent two fMRI sessions before
and after treatment. I would like to compare activation before and after
treatment on patient-by-patient basis and then do a higher level regression
analysis to see whether change in group activation predicts behavioural
improvement. For the within subject analysis I am using a higher level
t-test comparing the two before and two after fMRI sessions. My questions
is: Should I use a fixed effect analysis for this step?
Also, for the higher level (third level) analysis that includes the whole
group, should I use the COPEs as inputs? Hope this makes sense. Thanks -
Julius
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