AGE DEPENDENCY OF CHANGES IN CEREBRAL HEMOGLOBIN OXYGENATION DURING BRAIN ACTIVATION - A NEAR-INFRARED SPECTROSCOPY STUDY

We used near-infrared spectroscopy (NIRS) to study noninvasively the i nfluence of aging on changes in the local concentration of oxygenated hemoglobin ([HbO(2)]), reduced hemoglobin ([HbR]), and total hemoglobi n ([HbT] = [HbR] + [HbO(2)]) during activation of brain function. Youn g subjects (n = 12; age, 28 +/- 4 years) performing calculation tasks showed an increase in [HbO(2)] [mean (arbitrary units) +/- SD, 2.36 +/ - 1.07] and [HbT] (2.24 +/- 1.13) in the frontal cortex, while [HbR] ( -0.11 +/- 0.48) decreased. Elderly subjects (n = 17; age, 52 +/- 10 ye ars) showed a significantly lower mean increase (p < 0.05) in [HbO(2)] and [HbT] levels (1.21 +/- 1.38 and 0.72 +/- 1.41, respectively). Reg ression analysis supports the hypothesis of an age-dependent decline i n the activation-induced local increase in [HbO(2)] (y = -0.241x + 20. 062; r = -0.431, p < 0.05) as well as [HbT] (y = -0.346x + 22.496; r = -0.568, p < 0.05). We conclude that NIRS isa promising approach for s tudying changes in Hb oxygenation during brain activation in physiolog ical aging.