Frequency-Dependent Cerebral Blood Flow-Volume Coupling in Activated Human Visual Cortex

Ai-Ling Lin¹, Peter T. Fox¹

Neuronal activations elicit responses in cerebral blood flow (CBF) and volume (CBV). However, whether the flow-volume coupling persists unchanged or varies with brain activities in humans during brain functions remains unclear. In the study, relative CBF and CBV were measured with arterial spin labeling (ASL) and Gd-DTPA contrast agent, respectively, during visual stimulation at 4 and 8 Hz. The result shows that the flow-volume coupling (α value) is not constant, but stimulus frequency-dependent. The frequency-varying flow-volume coupling would facilitate our future understanding of BOLD mechanism and the determination of cerebral metabolic rate of oxygen metabolism (CMRO₂).