Here is the solution to my previous posting inquiring about
PPI in SPM5. First, Thank you Darren G, for your help.
To conduct PPI in SPM5 where I have the following
6 conditions:
Rest = Silence
Click = Clicking (A
non-vocal sound)
Whistle = A shrill coaches whistle
NFV Lang = A non -familier
Voice Reading non-ambiguous paragraphes aloud
NFV SON = A non-familiar
voice calling subject's name aloud
I want to compare NFV Lang with
NFV SON using PPI to see which voxels are correlated with a VOI of interest.
This is what worked:
First I CREATED VOI by :
§
After "Specifying
1st Level" I selected Results and SPM.Mat file.
§
Selected NFV Lang –
NFV SON – Rest contrast (that I had previously 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
Then set up for PPI
analysis by:
§
I clicked on PPI button
§
Selected corresponding
spm.mat file
§
Chose psychophysiolgoic ...
§
Sleeted saved voi.mat file
§
Included NFV Lang condition
with contrast weight = 1 (positive)
§
Included NFV SON condition
with contrast weight = -1(negative)
Then I set up a NEW MODEL
by:
First I changed directories
(so nothing would get written over)
§
Copied over my PPI file (that
was created from step above) to my new directory
§
Clicked on specify 1st
level
§
Selected Directory of Choice
§
Select Seconds or Scans
whichever is appropriate
§
Select HRF with Time derivatives
(if indicated)
§
NO CONDITIONS entered
§
Select the Regresssors
option (so that three regressor pop up windows appear)
Enter
in this order:
1.
Regressor 1: Name = Name
PPI.ppi or whatever you want
Value
= PPI.ppi (Make sure you use this case –SPM5 is case sensitive; the
values will automatically populate into this field after you press enter)
2.
Regressor 2: Name = PPI.Y
(or whatever you want to call it)
Value
= PPI.Y (Again the values will automatically populate into this field
after you press enter)
3.
Regressor 3: Name = PPI.P
(or whatever name you choose)
Value
= PPI.P
§
Click run
Then to Estimate the
model I:
Clicking on Estimate and
selected newly created spm.mat file (From the new directory )
Clicked run
To explore 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 Lang - NFV SOn) x Y,
while discounting the effects of Y and P.
the other contrast is -1 0 0
0 which looks at the opposite interaction.
To better understand the
above function you can go to:
http://www.umich.edu/~fmri/course/2005/files/spm2/spm_peb_ppi.m
Thanks again Darren G. for your help with the above
Theresa Louise-Bender Pape, Dr.PH,
MA, CCC-SLP/L
Career Development Transition Award Scientist
Department of Veterans Affairs
Rehabilitation Research & Development Service
Research Service, Hines
Research Health Scientist
Center for Management of Complex Chronic Care
Research Assistant Professor
Northwestern
Department of Physical Medicine and Rehabilitation
Clinical Research Scientist
Senior Associate
Northwestern
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