Hemodynamic Responses Following Brief Breath-Holding and Visual Stimulation Reconcile the Vascular Compliance and Sustained Oxygen Metabolism Origins for the BOLD Post-Stimulus Undershoot in Human Brain

Jun Hua¹, Robert Stevens¹, Alan J. Huang¹, James J. Pekar¹, Peter C.M. van Zijl¹

BOLD studies of visual stimulation show a post-stimulus undershoot, whereas breath-hold studies dont. BOLD/CBF/CBV/arterial-CBV dynamics following visual stimulation and breath-hold were measured to investigate which mechanism (vascular/metabolic) dominates the undershoot. After visual stimulation, arterial-CBV/CBF returned to baseline in ~8s/15s, respectively, while BOLD undershoot lasted for ~30s, during which elevated post-arterial-CBV (2.4+/-1.8%) and CMRO2 (10.6+/-7.4%) were observed. Following breath-hold, BOLD/CBF/CBV/arterial-CBV all recovered within ~20s and no BOLD undershoot, elevated post-arterial-CBV and CMRO2 were observed. These data suggest that both delayed post-arterial-CBV return and enduring oxygen consumption affect the undershoot, with contributions estimated as 20+/-16% and 79+/-19%, respectively, under our experimental conditions.