Computational modeling of the transient hemodynamic response in cerebral cortex

Neural activity triggers a vascular response in the brain that leads to transient changes in oxygen transport, and this mechanism is the basis for popular and powerful functional imaging methods. However, there is limited understanding of oxygen delivery to cerebral cortex both in steady state and during transient perturbations. In this study, a computational model for oxygen transport in the brain was developed and used to fit polarographic oxygen measurements during transient stimulation in cerebral cortex. The hemodynamic response function (HRF) was modeled with convection-diffusion transport in a four-compartment system (erythrocyte, intravascular, extravascular, and intracellular) that includes oxygen dissociation from hemoglobin. This model explained the dynamics of oxygen transport in cortex after brief visual stimulation, successfully fitting ~90% of experimental measurements within a realistic range of parameters for steady-state flow speed and oxygen consumption, as well as flow and oxygen uptake perturbations.