Brainmap: Effect of the end-tidal CO2 fluctuations on resting-state fMRI

Monday, September 15, 2014 - 13:30
Seminar room 2204, Bldg. 149, Charlestown Navy Yard

Ali Golestani, Ph.D.
Potsdoctoral fellow
Rotman Research Institute, Baycrest
Toronto, Ontario, Canada
 
The blood oxygenation level dependent (BOLD) signal measures brain function indirectly through physiological processes and hence is susceptible to global physiological changes. Specifically, fluctuations in end-tidal CO2 (PETCO2), in addition to cardiac rate variation (CRV), and respiratory volume per time (RVT) variations, have been known to confound the resting-state fMRI (rs-fMRI) signal. Previous studies addressed the resting-state fMRI response function to CRV and RVT, but no attempt has been made to directly estimate the voxel-wise response function to PETCO2. Moreover, the potential interactions amongst PETCO2, CRV, and RVT necessitate their simultaneous inclusion in a multi-regression model to estimate the PETCO2 response. In our recent work, we use such a model to estimate the voxel-wise PETCO2 response functions directly from rs-fMRI data of nine healthy subjects. We also characterized the effect of sampling rate (TR = 2 s vs. 323 ms) on the temporal and spatial variability of the PETCO2 response function in addition to that of CRV and RVT. In addition, we assess the test-retest reproducibility of the response functions to PETCO2, CRV and RVT. Furthermore we investigate the effect of voxel-wise physiological noise correction on the reproducibility of the connectivity measures. We found that despite overlaps across their spatial patterns, PETCO2 explains a unique portion of the rs-fMRI signal variance compared to RVT and CRV. We also found the shapes of the estimated responses are very robust against fMRI image sampling rate, although responses estimated from short-TR data have higher reproducibility.