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Dear SPMer:
  I have a basic question for the contrast definition. 
  If there is only 1 task (left hand tap, eg.), resting as control state. then, how will I enter the number in the Number of conditions/trails in the model speification. 1 or 2 ? 
   
  And,  in the RESULT step, how will I enter the number in the window of contrast manager ? 1 -1 0, or 1 0 0 (conditions=2). what the differences between 1 0(1 condition), 1 -1 0 and 1 0 0(2 conditions)? In the contrast manager, the sum of the definition values must be 0 ?
   
  Someone told me that the result of "1 -1 0(2 condition)" was better than that of "1 0 (1 condition)". But I compared them and found the activation of "1 0 (1 condition)" was stronger than "1 -1 0(2 condition)". What's the reason?
   
  In the above example which have only 1 actual task, if the correct specification number is "2" , I wonder why SPM permit "1",  "2" will be the minimum number in the model specification?
   
  Thanks a lot!
   
  Zhiqiang Zhang
  Nanjing University , China.
   

       
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