Evaluation of brain hemodynamics with functional near infrared spectroscopy during head-down tilt on young and healthy subjects

Human brain undergoes a number of physiological changes. Especially these changes contributes to optical properties of brain and can be observed with optical imaging methods in visible and near infrared light range. The aim of this study is, by using functional near infrared spectroscopy (fNIRS), with a specific protocol, observing oxygenation and blood volume with respect to time on young and healthy subjects. For this purpose, 5 healthy young male and 5 healthy young female are participated and measurements are taken from their prefrontal cortex during the experiment. When the subjects are in supine position, they are asked to move their heads down to their knees and stay in this position for 30 seconds. When this experiment is ended, oxygenation and blood volume changes were observed. fNIRS signals are analysed into two groups containing eight signals each and so they will represent the right and the left hemisphere of the brain. In each hemisphere, maximum and minimum points of blood volume showed no significant difference for male and female. (left hemisphere: V_min p=0.25, V_max p=0.12; right hemisphere: V_min p=0.07, V_max p=0.07). Without taking sex difference into account, V_min ve V_max values of right and left hemisphere are also not significantly different (respectively p=0.22, p=0.06). Therefore, this study implies that there is not a meaningful difference of brainhemodynamic responses during a head tilt test in adult subject group with respect to gender and laterality. fNIRS system hence possesses a potential to diagnose cerebrovascular diseases.