Subject-Specific BOLD fMRI Respiratory and Cardiac Response Functions Obtained from Global Signal

Maryam Falahpour¹, ², Hazem Refai², Jerzy Bodurka¹, ³

Slow changes in the heart rate and breathing pattern alter BOLD fMRI and can be misinterpreted as neural activation. It is common to employ respiratory and cardiac response functions (RRF, CRF) to map and remove the low-frequency physiological fluctuations from BOLD. However, both RRF and CRF have been analytically defined based on the average of multi-subject data and dont account for intra-subject differences. We propose a novel approach that employs subject-specific, individualized RRFi and CRFi obtained from the whole brain global signal (GS). Our subject-specific approach explains more variance in data without creating the problems caused by GS regression.