#1 and #3 are basically the same. If used as a task regressor, then a
contrast for it will be created. #2 is a parametric modulation. Probably
not what you want but see
http://freesurfer.net/fswiki/FsFastParametricModulation
Do you want to treat it as a nuisance variable or task? In any event, I
would probably recode it to make fixation=0 and non-fixation something else
On 5/2/15 5:34 PM, Xiaomin Yue wrote:
Hi,
I have a question related to how to make an appropriate design matrix
using fs-fast 5.3. Subjects’ eye movement was collected during an
experiment. Then, the data has been transformed to a continuous
variable with a number for each TR. The better fixation performance
has higher number. For example, a number would be 0 if subjects look
away from a target within a TR. In ideal situation, subjects should
keep his eyes on target all the time, so the variable should be 1 for
all TR. According to mkanalysis-sess documents, it seems that there
are three different ways to take into account of eye fixation
performance: 1) use it as an external task regressor; 2) use it as a
weight in the paradigm file (the fourth column); 3) use it as a
nuisance regressor. My question is what’s the difference between the
three methods? In my situation, which one is the best choice in my
situation?
I hope the question is clear. Thanks so much for your help.
Xiaomin
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