I wouldn't worry about the factors part. Just specify the conditions.
Here is some code that should help.
Download the tutorial Attention dataset from the SPM website. Also
download All*.tar from
http://www.martinos.org/~mclaren/ftp/Utilities_DGM
The attached files are also required.
Remember to make sure the downloaded files are in the matlab path.
>> SPMin.nscan=360;
>> SPMin.Units='scans';
>> SPMin.xVi='AR(1)';
>> SPMin.HP=128;
>> SPMin.timingfiles={'multi_condition.mat'};
The names of the three conditions are: NoAtten, Attention, and
Stationary. Here is an example of the Contrasts field structure. Make
this for all 26 combinations of conditions including compared against
fixation (use 'none').
>> SPMin.Contrasts(1).left={'NoAtten'};
>> SPMin.Contrasts(1).right={'Attention'};
>> SPMin.Contrasts(1).STAT='T';
>> SPMin.Contrasts(1).name='NoAtten_minus_Attention';
>> SPMin.Contrasts(1).MinEvents=1;
>> spm_firstlevel(SPMin)
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Office: (773) 406-2464
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On Thu, Jun 30, 2011 at 6:16 PM, Gina Joue <[log in to unmask]> wrote:
> As a related follow-up question: how are the factors and levels which you specify in the factorial design linked to the conditions and onsets? Does SPM match them automatically based on the order in which the conditions and the factors in the model are specified?
>
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