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.