Effects Of Acceleration-Induced Reductions In Retinal And Cerebral Oxygenation On Human Performance

BACKGROUND: Ischemic hypoxia induced by suprathreshold G-force loading can adversely affect vision, cognition, and lead to loss of consciousness (LOC). The purpose of this study was to determine whether reductions in cerebral oxygenation, caused by subthreshold G-forces (up to +4 G(z) and of limited durations that do not lead to LOC), would affect visual perception and working memory performance.METHODS: Sixteen subjects performed visual perception and working memory tasks both before and during G, exposures (+1, +2.2, +3, +4 with leg pressurization, +4 with leg and abdomen pressurization) within a human-use centrifuge.RESULTS: As measured using near-infrared spectroscopy, blood oxygenation over medial prefrontal cortex was similar in the +1 and +2.2 G(z) conditions, but was reduced to a similar extent in the +3 and +4 G(z) conditions. In parallel, visual perception accuracy was reduced in the +3 and +4 G(z) conditions, with no difference between the +3 and +4 G(z) conditions. No change in reaction time was seen. Conversely, neither accuracy nor reaction time changes were observed for the visual working memory task.DISCUSSION: These results indicate that although visual working memory is not affected, the ability to visually discriminate between stimuli is reduced at G-forces as low as +3 and +4 G(z). This may have important ramifications for pilots who are routinely subjected to such forces.