Real-time tracking of brain oxygen gradients and blood flow during functional activation

Cerebral metabolic rate of oxygen ( $$ ) consumption is a key physiological variable that characterizes brain metabolism in a steady state and during functional activation.

We aim to develop a minimally invasive optical technique for real-time measurement of $$ concurrently with cerebral blood flow (CBF).

We used a pair of macromolecular phosphorescent probes with nonoverlapping optical spectra, which were localized in the intra- and extravascular compartments of the brain tissue, thus providing a readout of oxygen gradients between these two compartments. In parallel, we measured CBF using laser speckle contrast imaging.

The method enables computation and tracking of $$ during functional activation with high temporal resolution ( $$ ). In contrast to other approaches, our assessment of $$ does not require measurements of CBF or hemoglobin oxygen saturation.

The independent records of intravascular and extravascular partial pressures of oxygen, CBF, and $$ provide information about the physiological events that accompany neuronal activation, creating opportunities for dynamic quantification of brain metabolism.