The Relationship Between Cerebral Blood Flow Characteristics and Mathematical Processing in Normoxia and Normobaric Hypoxia.

Abstract

Previous research suggests that middle cerebral artery flow velocity remains unchanged at altitudes up to 6,400m, and that cerebral oxygenation and cognitive function decline. PURPOSE: The purpose of this study was to investigate the relationships between cerebral blood flow characteristics, peripheral oxygen saturation, and mathematical performance in normobaric hypoxia (NH) and normoxia (N). METHODS: Nine participants (5 male) completed a VO2 max test in NH and in N (sessions 1 and 2) followed by two experimental sessions also in NH and N (sessions 3 and 4). The experimental sessions began with baseline assessments of peripheral blood oxygen saturation (SaO2), mathematical processing (TP), frontal lobe oxygenated hemoglobin saturation (CeO2Hb), and middle cerebral artery flow velocity (MCAfv) at min 0. These variables were measured again after 30 min of acclimation, during the final 5 min of a 20 min cycling protocol (60% VO2max), and at min 1, 15, 30, and 45 of recovery. CeO2Hb, SaO2, and MCAfv were first analyzed for colinearity using a Pearson Correlation analysis. Results indicated that MCAfv was significantly correlated to CeO2Hb (r2=.349, p=.01), but not to SaO2 (r2=.02, p=.885). Backwards regression analyses were then run with TP as the dependent variable and MCAfv and SaO2 as the independent variables for NH, N, and the combined conditions (COMB). RESULTS: In the N condition, neither the model including both predictors (SaO2 and MCAfv) nor the model only including SaO2 were significant predictors of TP (R2=.036, F=.961, p=.389 and R2= .036, F=1.957, p=.168, respectively). In the NH condition, the model including both SaO2 and MCAfv was a significant predictor of TP (R2=.216, F=7.040, P=.002), with MCAfv contributing the most to the model (B= −.404, P=.001). Similar results were found in the COMB condition (MCAfv only model, R2= .046, F=5.163, p=.025). CONCLUSIONS: Results from this study suggest that middle cerebral artery flow velocity is a significant predictor of mathematical performance, and that this relationship may be more pronounced in hypoxia. This information may be valuable to individuals whose occupation requires them to use mathematical processing skills while in hypoxia.