Applications

Neuro-Vascular Coupling

Neurovascular coupling is one of the key concepts for the investigation of brain functions. The higher rate of oxygen metabolism of cortical tissue following the onset of a stimulus is commonly correlated with an increase in blood flow. This increase is linked to a higher oxygen supply by the blood to the tissue and compensates the higher oxygen extraction.

Consequently, there is an increase in oxygenation, i.e. an increase in the concentration of oxygenated haemoglobin and a decrease in the deoxygenated haemoglobin. The BOLD (Blood Oxygen Level Dependent) contrast in functional magnetic resonance imaging (fMRI) exploits this for an imaging of cortical function. Tissue oxygen monitoring using white-light reflective spectroscopy is well suited to record local changes in oxygenation, and functional related changes in haemoglobin from the opened cortex. Contrary to BOLD which is sensitive to changes in deoxygenated haemoglobin concentrations, the optical tissue oxygen monitoring is able to retrieve both the oxygenated and deoxygenated haemoglobin concentrations. Additionally, the oxygen saturation of the haemoglobin in the microcirculation can be obtained.