Biophysical simulations using realistic Vascular Anatomical Networks predict BOLD response attenuation at high stimulation frequencies

Motivation: BOLD response amplitudes decrease with faster stimulation frequency. The extent to which this is caused by hemodynamics is unclear. Goal(s): To investigate the extent to which hemodynamics within the microvascular network impact BOLD response amplitude with increasing stimulus frequency. Approach: Using realistic reconstructions of cortical microvasculature, we simulated hemodynamic responses to oscillating stimuli. We implemented arterial dynamics such that dilation propagated across the arterioles, with passive compliant ballooning of capillaries and veins. Results: We found that transit time heterogeneity due to dilation propagation within the microvascular network impacted flow and oxygenation responses, resulting in attenuated BOLD responses with increasing stimulus frequency. Impact: The role of vascular anatomy in BOLD responses attenuation at higher-frequency sensory stimulation is unclear. We apply biophysical modeling to investigate whether the cerebral cortical microvascular network influences BOLD dynamics and generates discrepancies between blood volume and oxygenation responses.