If you set up the following:
EV1 EV2 EV3 EV4
Mean1 1 0 0 0
Mean2 0 1 0 0
Mean3 0 0 1 0
Mean4 0 0 0 1
You will analyse where each your conditions activates on average in the brain.
If you set up the following:
EV1 EV2 EV3 EV4
Mean1>Mean2 1 -1 0 0
Mean1>Mean3 1 0 -1 0
Mean1>Mean4 1 0 0 -1
Mean2>Mean1 -1 1 0 0
Mean2>Mean3 0 1 -1 0
Mean2>Mean4 0 1 0 -1
Mean3>Mean1 -1 0 1 0
Mean3>Mean2 0 -1 1 0
Mean3>Mean4 0 0 1 -1
Mean4>Mean1 -1 0 0 1
Mean4>Mean2 0 -1 0 1
Mean4>Mean3 0 0 -1 1
You will analyse where each your conditions differs from one another in the brain.
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 Heather C. [[log in to unmask]]
Sent: Thursday, July 23, 2009 12:00 PM
To: [log in to unmask]
Subject: [FSL] Mean contrast?
Hello FSL experts!
I have 4 experimental conditions and would like to obtain the mean activation for
all conditions. Is the correct contrast [1 1 1 1 ]?
I thought that if you had a contrast such as [1 1 1 1 ], it meant you wer
weighting each condition equally in the model. Is that true?
Does [1 1 1 1] give me areas in which all 4 conditions are contributing equally?
Or does it give me the overall mean? And if it is the overall mean, which formula
is it using?
Thank you for your help!
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