BOLD temporal SNR bias and variance across the HCP population as a function of cortical B0-orientation and orientation variability

BOLD fMRI signals vary with the orientation of the cortex to the B0-field as extravascular susceptibility effects vary with the orientation of the cortical pial vasculature. This creates regional tSNR biases with cortical folding. Certain cortical folds are more homogenous across the population than others and orientation variability across subjects should introduce tSNR variability at the group-level. Here, we use HCP 3T rs-fMRI data to show that B0-orientation contributes to within-subject tSNR bias and orientation variability contributes to tSNR variance across subjects. We found that functional connectivity networks with more perpendicular orientation exhibit higher tSNR and networks with high orientation consistency have lower tSNR variability.