Dear Maxwell,
What is the best way to compare
activationareas common between two tasks.
I have 8 subjects doing an active finger movement, 2 runs- analyzed and
have
con files (8 from each run)
I have same 8 subjects doing passive finger movement, 2 runs-analyzed and
I
have con files (8 from each run)
Now I need to know differences in brain activation between 2 tasks-do i
use
RFX or conjunction analyses?
The difference in activation is most simply addressed with a two sample
t-test at the second (between-subject) level. This is a RFX
analysis.
To use conjunctions over subjects would require a first-level analysis
with a large FFX model in which you tested for a conjunction
of differential activations over subjects. Rejecting the
[conjunction] null
would allow you to say that that there was a greater activation in
active,
relative to passive, in one or more subjects.
In order to compare
normals with Spinal cord patients, which confiles should
I use for comparison with 8 SCI subjects who preformed same
tasks
This calls for a conventional RFX analysis because you want to make
an inference about the populations. Conjunctions analyses over
subjects
would not be appropriate here. I would use all (2 runs x 8 subjects
x 2
conditions x 2 groups) con images in a simple ANOVA model at the
second level. This would include the effects of run, condition and
group.
You could then test for the main effects of group, condition and
critically
the group by condition interaction. If the latter was significant
you could
proceed to examine the simple main effects of group within the passive
and
active levels of the condition factor. Note that a single model
enables you to do
all these tests just using different contrasts (and has the greatest
degrees
for freedom for inference)
Q2; what is the
best way to compare pilot data if I have controls- 16
patients versus 2 SCI patients- need to know common areas and
differences
in activation using active and passive tasks
Use exactly the same ANOVA design as above but this time there are
only 2 subjects in the patient group. The common activations can
be
defined by the main effect of condition and the differences identified
though
the interaction.
I hope this helps - Karl