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Nov 16, 2017 03:11 PM | Simone Viganò
Connectivity measures for test-retest fmri
Dear experts,
I'm having trouble in defining the correct connectivity measures to implement in my analysis pipeline for a test-retest fMRI experiment. I hope some of you could give me any suggestion on how to proceed, or confirm/correct what I already figured out by myself.
I have 21 subjects performing two fMRI sessions, one pre-learning and one post-learning.
During pre-learning session subjects perform task A. During post-learning session they perform task B and then task A again. We have event-related design in both the sessions.
Now, I have been able to observe activity in three ROIs: regions X and Y appears in all the tasks, while region Z only during task B (post learning).
Here comes the connectivity issues I would like to attack:
1) is the functional connectivity between X and Y during pre-learning session significantly higher than zero, at group level?
2) is this functional connectivity between X and Y different between task A (pre-learning) and both the tasks B and A on post-learning? (e.g. effects of learning and of learning x task)
3) is the FC between X,Y, and Z on post-learning session higher than zero and higher than the first learning session?
Please be patient but this is my very first experience with connectivity (and this is also my first fMRI experiment!). Here's my idea about how to proceed:
1) here I would use an ROI-to-ROI analysis between regions X and Y. I would use the weighted GLM as option, and I would test the significance at group level as a classical 2nd level analysis in SPM. If this is right, does this step account for task induced co-activation? That is, does this step use the residuals after the task model has been regressed out?
2) here I would use ROI-to-ROI analysis with gPPI, because I need to know whether and how this connectivity changes between pre and post learning.
3) same as before: gPPI to see wether connectivity with the "new" region Z emerges after learning in one of the two tasks, compared with pre learning session.
Hope it was clear enough.
Thank you very much for your time!
s
I'm having trouble in defining the correct connectivity measures to implement in my analysis pipeline for a test-retest fMRI experiment. I hope some of you could give me any suggestion on how to proceed, or confirm/correct what I already figured out by myself.
I have 21 subjects performing two fMRI sessions, one pre-learning and one post-learning.
During pre-learning session subjects perform task A. During post-learning session they perform task B and then task A again. We have event-related design in both the sessions.
Now, I have been able to observe activity in three ROIs: regions X and Y appears in all the tasks, while region Z only during task B (post learning).
Here comes the connectivity issues I would like to attack:
1) is the functional connectivity between X and Y during pre-learning session significantly higher than zero, at group level?
2) is this functional connectivity between X and Y different between task A (pre-learning) and both the tasks B and A on post-learning? (e.g. effects of learning and of learning x task)
3) is the FC between X,Y, and Z on post-learning session higher than zero and higher than the first learning session?
Please be patient but this is my very first experience with connectivity (and this is also my first fMRI experiment!). Here's my idea about how to proceed:
1) here I would use an ROI-to-ROI analysis between regions X and Y. I would use the weighted GLM as option, and I would test the significance at group level as a classical 2nd level analysis in SPM. If this is right, does this step account for task induced co-activation? That is, does this step use the residuals after the task model has been regressed out?
2) here I would use ROI-to-ROI analysis with gPPI, because I need to know whether and how this connectivity changes between pre and post learning.
3) same as before: gPPI to see wether connectivity with the "new" region Z emerges after learning in one of the two tasks, compared with pre learning session.
Hope it was clear enough.
Thank you very much for your time!
s