Optical Imaging of Microvascular Function in the Brain

Maintaining adequate cerebral blood flow is essential for normal brain function. Cerebral arteries are responsible for providing sufficient blood supply, which is dependent on systemic blood pressure and thus cardiac output. Cerebral capillaries play a critical role in delivering blood to meet the local needs of neural activity. Their narrow lumen interacts with blood cells, creating resistance to blood flow in the parenchymal tissue. Therefore, the relationship between arterial blood pressure and capillary resistance is critical in determining blood perfusion in the brain. However, the regulatory mechanism of capillary resistance has received less attention compared to the management of arterial blood pressure in maintaining healthy cerebral perfusion. This article summarizes the methodological contributions of optical imaging to the characterization of capillary resistances by microvascular function in the brain, including: i) three-dimensional imaging and quantification methods used in preclinical studies to determine spatial variations in microvascular structures in the cortex, ii) fluorescence imaging techniques for mapping the temporal dynamics of microvascular flow, and iii) understanding microvascular function in response to global changes induced by systemic physiology and local variations in neural network activities. Finally, potential technical advances in optical tools for diagnosis of brain microvascular function are discussed.