Hello!

I have a repeated measure dataset, where all subjects were scanned twice (i.e., pre & post) with an interval of 7 days between scans by fMRI. After analyzing by FSL standard pipeline, I got very weird group-level results using insular as ROI.

Pre: the functional connectivity between insular and S1 is Bilateral NEGATIVE!!! (with a large number of voxels) Post: the functional connectivity between insular and S1 is positive (with a small number of voxels) And paired t-test (Post > Pre) found large areas of difference in the sensorimotor region.

This result seems very strange to me as previous research has suggested that the test-retest reliability of resting-state functional connectivity is quite high. However, I am still unclear as to why the sensorimotor region appears to have a negative correlation during the pre-test.

Do any experts have any suggestions on this result? Are there any additional pre-processing methods such as denoising or motion correction that could improve the results?

Many Thanks!!!