Symboilc GLT Question

AFNI Message Board
1

Hello,
I have a block design where I have subject move “Left Hand”, “Right Hand” and “Both Hands” in random order.

I am interested in knowing what regions “Both Hands” activation is the greatest and what regions “Both Hands” activation is unique.

For the first question I tried to set-up the Symbolic GLT as:

BothHand -(LeftHand -RightHand)…this has resulted in errors that are common with the GLTsymtest documentation but I still don’t know how to fix it.

Further, I’m not really sure how to set up a GLTsymtest for the second question where I would like to know where the Both Hands activation is unique.

Can anyone provide advice?
Thanks

2

Are you performing the analysis at the individual or population level?

what regions “Both Hands” activation is the greatest

For this, you can conduct two separate tests: (1) “Both Hands” > “Left Hand”, and (2) “Both Hands” > “Right Hand”. Then obtain the conjunction of the two.

what regions “Both Hands” activation is unique

By “unique” do you mean the brain regions where “Both Hands” is activated but neither “Left Hand” nor “Right Hand”? If so, you’re hitting the territory where the conventional statistics cannot directly address: you can’t use p > 0.05 as an evidence of a lack of an effect. If you’re willing to perform the analysis at the ROI level, it might be possible to make such an inference under the Bayesian framework: https://afni.nimh.nih.gov/afni/community/board/read.php?1,157054,157054#msg-157054

3

For right now I’m doing analysis at the individual level. Once I acquire more date I’ll do it at the group level.

Can you refer me to a document that lays out what syntax Symbolic GLT accepts? I tried inputting “Both Hands” > “Left Hand” and received errors. Can that be written as BothHands -LeftHand?

For the second question I am trying to do something similar to:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4486387/

In their paper they performed a conjunction analysis using (BothHands ∩ ¬(RightHand ∪ LeftHand)). How would I do something like this in AFNI?

Thanks for your help.