Illuminating Brain Health: Using Diffusive Optical Imaging to Study Vascular Health and Reactivity
Aerobic fitness has been related to the level of cognitive decline that occurs with normal aging. Some of this relationship may be explained by vascular health in the brain, including arterial elasticity. However, measuring vascular health from outside the head is difficult. Near-infrared light can propagate through the skull and is absorbed by hemoglobin in the blood, allowing changes in blood dynamics to be detected outside the head. Therefore, optical imaging can be used to study vascular health and reactivity non-invasively in human participants. We have been studying a novel method to measure arterial elasticity non-invasively in the brain by quantifying the length and shape of the pulse wave, which can be measured using optical methods. Furthermore, we have been relating this measure to the shape and timing of the hemodynamic response to breath-holding, a measure of vascular reactivity. The hemodynamic response in adults (aged 55-87) with higher elasticity reacts to and recovers faster to breath-holding than adults with lower elasticity. We expect further investigation to yield fruitful insights into the mechanisms by which vascular health may impact cognitive fitness.