Decoupling of the short‐term hemodynamic response and the blood oxygen concentration

Abstract

Neuronal activation leads to an increase in the local cortical perfusion. The exact regulatory mechanisms leading to these changes are still unknown. To elucidate the role of oxygen in the initial hemodynamic regulation, a disactivation paradigm was performed with fMRI. A stimulus was applied following a previous extended activation in order to evoke physiological variations of the local oxygen concentration. The results demonstrate that the initial hemodynamic response time is independent of the local blood oxygen concentration. Copyright © 2001 John Wiley & Sons, Ltd. Abbrevations used: BOLD blood oxygenation level dependent CBF cerebral blood flow CMRO₂ cerebral metabolic rate of oxygen fMRI functional magnetic resonance imaging FOV field‐of‐view GE‐EPI gradient echo–echo planar imaging