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Dear SPM experts


I´m trying to run a gPPI analysis using the Donald McLaren´s toolbox and I
would like to ask you some questions. My task, it´s an even related design
divided in 3 runs (213, 218 and 214 volumes respectively) with 8 conditions
(conditions are the same across runs). SPM matrix for first level analysis
was performed with SPM5.

  I introduce parameters in P structure as follow:


P =

Subject={' subject_1'}

VOI={ 'F:\gppi \ROIS\ROI_Amygdala_LB.img'}

Region={ 'ROI_Amygdala_LB'}

SPMver= 5

Directory='F:\ gppi \ subjects\subject_1\ '

Estimate= 1

Contrast={'Omnibus F-test for PPI Analyses'}

Extract= 'mean'

Tasks={'1' 'A' 'B' 'C' 'D' 'E' 'F' 'G' 'H'}

Weights= []

Maskdir= []

Equalroi= 1

FLmask=0

VOI2={}

Analysis= 'psy'

Method= 'cond'

CompContrasts= 1

Weighted= []

Contrasts=

P.Contrasts.name='A>B'

P.Contrasts.STAT='T'

P.Contrasts.left={'A'}

P.Contrasts.right={'B'}

P.Contrasts.Weighted=[]

P.Contrasts.Prefix={'Sn(1)' 'Sn(2)' 'Sn(3)'}

P.Contrasts.Contrail= {'bf(1)'}

P.Contrasts.MinEvents=1



Matlab returns the subsequent error:

'Program will exit. Contrast cannot be defined.'



1) My first question is, is there something wrong in P structure?



Since the erros seems to related to contrasts generation, I tried to avoid
that toolbox generate contrasts automatically. Then, I performed with SPM
an Omnibus F-test (named Omnibus) and changed in above P structure the
subsequents parameters:


Contrast= {'Omnibus' }


CompContrasts= 0 (following the guide in this way any contrast will be
generated)


Then, the matrix was generated and estimated, but contrasts as  expected,
were not defined   (Note that if I change only one of the two parameters
above, toolbox doesn´t run and the same error appears; 'Program will exit.
Contrast cannot be defined.').


The resulting matrix is as follow:


A  B  C  D  E  F  G  H  PPI_A  PPI_B  PPI_C  PPI_D  PPI_E  PPI_F  PPI_G
 PPI_H   ROI_seeddtc  and 6 rp_mov (for run 1 run2 and run3)


2) My second question is if the correct contrast to obtain connectivity
differences during A>B, is simply put 1 for PPI_A regressor in each run, -1
for PPI_B  regressor in each run and 0 for any other columns?


Thanks in advance.


Regards

Victor.