Enabling brain-wide mapping of directed functional connectivity at 3T via layer-dependent fMRI with draining-vein suppression

Motivation: Mapping brain-wide directed functional connectivity demands techniques with high spatiotemporal resolution yet current methods fall short. Goal(s): To improve spatial specificity of GE-BOLD EPI by reducing draining-vein contamination without compromising speed. Approach: Incorporating velocity-nulling (VN) gradients into a GE-BOLD fMRI sequence at 3T. We also integrated NORDIC denoising to enhance signal sensitivity. Results: The VN fMRI method demonstrated decent spatial specificity, evidenced by identifying double-peak activation patterns within the M1 area during a finger-tapping task. This technique showed enhanced robustness across participants compared to conventional fMRI. Our findings on directed functional connectivity reveal layer-specific relationships that closely align with the existing literature. Impact: Leveraging its comprehensive brain coverage and efficient scan time, VN fMRI has yielded promising results in directed FC studies. Given the widespread accessibility of 3T scanners, we anticipate this development will have a significant impact across multiple neuroscience research domains.