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Abstract #1651

Low-Frequency Respiration Related Signals in Resting State FMRI: A Comparison of End-Tidal CO2 and Respiration Volume Per Time

Kevin Murphy1, Rami K. Niazy1,2, C. John Evans1, Richard G. Wise1

1Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff, UK; 2Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia

Functional connectivity analysis exploits coherent low-frequency oscillations in the BOLD signal. Fluctuations in arterial CO2 are low-frequency and can confound interpretation of neuronal activity. Two correction methods that attempt to remove this noise source use end-tidal CO2 and RVT measures to regress breathing-related changes from the BOLD time series. We show that a lack of similarity between the CO2 and RVT regressors and the variance explained by them implies that each is measuring a different portion of the noise related to fluctuations in breathing and arterial CO2. This suggests that both measurements are required for accurate removal of such noise.