theresa:
==============Original message text===============
On Thu, 27 Sep 2007 1:49:51 pm CDT "Pape, Theresa" wrote:
All
I just tried PPR with SPM5 (using Matlab 7.10) for the first time and I
am pretty sure that I have made an error in my logic or in my
procedures, but I am not sure.
I have 6 conditions:
Rest = Silence
Click = Clicking (A non-vocal sound)
NFV SON = A non-familiar voice calling subject's name aloud
Bell = a school bell ringing
Whistle = A shrill coaches whislte
NFV Lang = A non -familiar voice reading non-ambiguous paragraphs aloud
I want to compare NFV SON with NFV Lang using PPI to see which voxels
are correlated with a VOI of interest.
This is what I did:
I CREATED VOI by :
* After "Specifying 1st Level" (Model.mat file is Attached FYI), I selected Results and
SPM.Mat file.
* Selected NFV SON - NFV Lang contrast (that I had already created),
* Selected a group of voxels in the frontal area (Near Superior Frontal Gyrus),
* Clicked on VOI button
* Named the VOI
* Selected sphere with 6 mm
YES
Then set up for PPI analysis by:
* I clicked on PPI button
* Selected corresponding spm.mat file
* Chose psychophysiolgoic ...
* Seleted saved voi.mat file
* Included NFV SON condition with contrast weight = 1 (positive)
* Included NFV Lang condition with contrast weight = -1 (negative)
YES
Then I added the ppi as a multiple regressor by:
* I changed directories (so nothing would get written over)
YES
* Clicked on specify 1 st level
YES
* Loaded my previous model (attached), but added ppi as a multiple regressor
NO
YOU NEED A NEW MODEL. IT SHOULD HAVE 3 USER SPECIFIED REGRESSORS AND NO CONDTIONS.
THE THREE REGRESSORS ARE
- PPI.ppi
- PPI.Y
- PPI.P
* Clicked run
USING THE NEW MODEL
Then to Estimate the model I:
* Clicking on Estimate and selected newly created spm.mat file
* Clicked run
YES
TO LOOK AT RESULTS YOU CAN HAVE 2 CONTRASTS THAT LOOK AT PPI. The first is
1 0 0 0
which means
1 0 0 0
^ ^ ^ ^
ppi y p mean
assuming you put regressors in that order.
This will look at areas showing activation relative to the interaction of
(NFV SON - NFV Lang) x Y, while discounting the effects of Y and P.
the other contrast is -1 0 0 0 which looks at the opposite interaction.
darren
|