Hi Zhang
> 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 ?
I would go for 1 condition; the resting state being implicitly modelled
> 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 ?
well if you model one condition just enter 1
if you model 2 conditions enter 1 -1 (activation > rest)
when contrasting 2 conditions you will have to have the sum = 0,
otherwise you can also have a look at each regressor separately (1 0
then 0 1)
> 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?
because the rest is implicitly modelled you only have to estimate the
activation and thus already win 1 df ; in addition, although SPM manages
well rank deficient matrices I guess you get a better estimate if your
model is not rank deficient
> 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?
well don't get this one .. you can enter as many conditions as you want ...
Hope this helps
cyril
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