The effects of hypoxia on reaction time and movement time components of a perceptual—motor task

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Abstract
It has previously been demonstrated that hypoxia disrupts performance on a visual SCRT (serial choice response time) task. Two experiments were conducted to examine further the nature of this disruption. Hypoxia was induced with low-oxygen mixtures and SaO2 (arterial oxyhaemoglobin saturation) was held at a level equivalent to an altitude of approximately 4700 m. In experiment 1, choice reaction time was measured with a version of the SCRT task that eliminated movement time. Hypoxia increased the intercept but not the slope of the Hick-Hyman function. In experiment 2, movement time was measured with a reciprocal tapping task. Hypoxia increased not only the slope of Fitts’ function but also the slopes produced when target width and movement amplitude were analysed separately. In both experiments the error rate was held constant. These results indicate that hypoxia disrupts the reaction time and movement time components of SCRT performance. It is proposed that reaction time is slowed rather than ‘blocked’ and that decreased brightness sensitivity contributes to this slowing but the choice processing stage does not. Movement time is also slowed due to a disruption of both the aiming and ballistic processes controlling movement.