Hello All,
I have found an issue when working with 3dretroicor. I recently collected a resting state data set along with respiratory and cardiac data using a GE 3T Scanner and Version 11 Software Pack. When running the physiological data through 3dretroicor and seeding a region in the ventral portion of the brain, I found large amount of potentially spurious correlation. In fact, it appears that there is a network on induced spurious correlations in the ventral portion of the brain that is negatively correlated with the dorsal portion of the brain. While trying to uncover the problem, I re-ran the data without including the 3dretroicor step to see how it would work without including physiological parameters. This previously mentioned spurious correlation was not present. This lead me to test each component of the physiological data separately with 3dretroicor to see if the respiratory or cardiac fluctuations were causing the problem. Unfortunately, the spurious correlations were present in both. I then consulted with Dr. Rasmus Birn to see what his take was on it, and he provided me some code that he uses to handle his physiological data. The results from this test did not include the spurious correlations in the ventral portions of the brain. I had a problem uploading images to this post directly and I would like to share the images I have generated for help in feedback. Let me know how I can go about doing that and I will get on it right away. I look forward to any insight that might help clear this up in my mind as to what I'm doing wrong with the application of 3dretroicor or if the error is in the program itself.
Thanks,
Ben