help
help > RE: Possible to do '3rd' or '4th' level analyses with PPI?
Aug 28, 2021 06:08 PM | Alfonso Nieto-Castanon - Boston University
RE: Possible to do '3rd' or '4th' level analyses with PPI?
Hi Ben,
Yes, that sounds perfectly fine, I would suggest simply running standard seed-to-voxel analyses using weighted-GLM, that will compute a separate connectivity map for each of the four individual conditions, and then in the second-level analysis tab simply select those four conditions and enter the desired between-conditions contrast (e.g. if the conditions are sorted as Neutral-OFF, Neutral-ON, Rewarding-OFF, Rewarding-ON, and you would like to evaluate the reward-by-DBS interaction the between-conditions contrast would be "1 -1 -1 1"; see http://www.conn-toolbox.org/fmri-methods... for a few more details and examples)
Hope this helps
Alfonso
Originally posted by Benjamin Davidson:
Yes, that sounds perfectly fine, I would suggest simply running standard seed-to-voxel analyses using weighted-GLM, that will compute a separate connectivity map for each of the four individual conditions, and then in the second-level analysis tab simply select those four conditions and enter the desired between-conditions contrast (e.g. if the conditions are sorted as Neutral-OFF, Neutral-ON, Rewarding-OFF, Rewarding-ON, and you would like to evaluate the reward-by-DBS interaction the between-conditions contrast would be "1 -1 -1 1"; see http://www.conn-toolbox.org/fmri-methods... for a few more details and examples)
Hope this helps
Alfonso
Originally posted by Benjamin Davidson:
Hi Alfonso,
I have 6 patients with deep brain stimulators in the nucleus accumbens. In each, I performed a block-design fMRI task, where they viewed neutral and 'rewarding' pictures. I performed the fMRI run with the DBS activated, and also with the DBS OFF (randomized order). So, 2 fMRI runs for each subject. In addition to performing a task-based fMRI activation study (which I did using FSL-FEAT), I'd like to do a connectivity analysis using CONN, but I'm struggling with the contrasts/conditions. The contrast of interest for each subject is 'rewarding' pictures vs 'neutral' pictures (1 -1), but I'd really like to know how this is affected by turning the DBS ON.
For each subject I've created conditions with their custom timings (Neutral-OFF, Neutral-ON, Rewarding-OFF, Rewarding-ON). Is it possible to use these 4 conditions, in a seed-to-voxel analysis, to model the change in connectivity to an ROI, for the effect of looking at a 'rewarding' image vs a neutral image? Since I'm using a block design, I've been working in the weighted-GLM mode, because I read somewhere on this forum that this may be appropriate for block-design tasks. I think this would be like a 3rd or 4th level analysis in FSL...
Thanks in advance for any help!
Ben
I have 6 patients with deep brain stimulators in the nucleus accumbens. In each, I performed a block-design fMRI task, where they viewed neutral and 'rewarding' pictures. I performed the fMRI run with the DBS activated, and also with the DBS OFF (randomized order). So, 2 fMRI runs for each subject. In addition to performing a task-based fMRI activation study (which I did using FSL-FEAT), I'd like to do a connectivity analysis using CONN, but I'm struggling with the contrasts/conditions. The contrast of interest for each subject is 'rewarding' pictures vs 'neutral' pictures (1 -1), but I'd really like to know how this is affected by turning the DBS ON.
For each subject I've created conditions with their custom timings (Neutral-OFF, Neutral-ON, Rewarding-OFF, Rewarding-ON). Is it possible to use these 4 conditions, in a seed-to-voxel analysis, to model the change in connectivity to an ROI, for the effect of looking at a 'rewarding' image vs a neutral image? Since I'm using a block design, I've been working in the weighted-GLM mode, because I read somewhere on this forum that this may be appropriate for block-design tasks. I think this would be like a 3rd or 4th level analysis in FSL...
Thanks in advance for any help!
Ben
Threaded View
| Title | Author | Date |
|---|---|---|
| Benjamin Davidson | Aug 21, 2021 | |
| Benjamin Davidson | Aug 29, 2021 | |
| Alfonso Nieto-Castanon | Aug 28, 2021 | |