Li Bei wrote:
>Dear Juan Jose Lull Noguera :
>
> Thank you for helping me.
> There are some other questions.
>
> In my exp. described in last letter
>
>
>> My experiment is designed like this:
>> CACBCACBCACB ,where C means control,A means
>>stimulus 1,B means stimulus 2, and where are 10 scans
>>for each character
>>
>>(A,B,C),so there are 120 scans total .
>> In fmri design, i specify 3 conditions ,for
>>
>>
>A,B,C.
>
>
>> Vector for A is [10 50 90]
>> vector for B is [30 70 110]
>> vector for C is [0 40 80]
>>
>>
>
>Queston1: what's the meaning of F contrast of [1 -1]
>if i defined condition1 [10 30 50 70 90 110]
>condition2 [0 20 40 60 80 100]? A and B are both
>visual stimuli, and they are slightly different in
>context. Does this F-contrast mean activation and
>deactivation of a combination effect of A and B?
>
>
>
Yes, I think so. By combination you should understand areas activated
(and also deactivated) for both visual conditions. You could test this
with your other design (three conditions, A, B and C) with an F
contrast: [0.5 0.5 -1], I think. With that same design, you could also
test areas (de)activated for A and also for B (showing areas
(de)activated for A and not B; and areas (de)activated for B stimulus
and not A; and also common areas of (de)activation), with an F contrast:
[1 0 -1;0 1 -1].
>Question2: what's the vector of the F-contrast
>"effects of interest" ?
>
>
>
I don't see the meaning of effects of interest with this other design.
If your design was:
A: [10 50 90]
B: [30 70 110]
(no C defined), then effects of interest would be the F contrast I
defined in the last paragraph
P.S. - I'm already waiting for corrections from the list :)
>Thank you
>
>Li Bei
>
>
>
>=====
>Bei Li
>Institute of Neuroinformatics
>Dalian University of Technology
>2 Ling Gong Rd, Dalian 116023, China
>Email:[log in to unmask]
>
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