Auditory Discrimination and Short Term Memory are Preserved during Simulated Altitude and Moderate Intensity Exercise.

Abstract

PURPOSE: This study was conducted to examine the cognitive and neurophysiological effects of acute exposure to simulated moderate and high altitudes at rest and during exercise to examine whether short term memory or auditory oddball task performance were affected beyond a certain threshold of simulated altitude and whether exercise improves or worsens cognitive function during these conditions. METHODS: Fourteen recreationally active college students (M=9, F=5) aged 18-35 participated in this study, which consisted of six experimental days, with three simulated altitude conditions: sea level (SL), simulated moderate altitude (MA; 15.4% FIO2, ~2400 m) or simulated high altitude (HA; 12.8% FIO2, ~3900 m); and two exercise conditions: rest or moderate intensity cycling exercise at 60% altitude-specific peak power output, in a randomized-order, crossover design. Accuracy and reaction time on an auditory oddball task and a Sternberg memory task were assessed, alongside the amplitudes and latencies of their associated event-related potentials. RESULTS: Exercise improved auditory reaction time, regardless of altitude (p<0.01), though task accuracy was not affected under any condition. In addition, simulated altitude induced lower P300 amplitudes and slower latencies during the auditory oddball task (p<0.01), while exercise improved latencies at HA and SL, but not at MA (p=0.03). Sternberg memory task behavioral performance was not affected by either simulated altitude or exercise. However, P200 latency was slowed during exercise trials (p=0.02) as well as during MA trials (p<0.01). CONCLUSIONS: Acute exposure to simulated moderate and high altitudes may not significantly impact short term memory and auditory discrimination. On the other hand, an acute bout of moderate intensity cycling exercise may improve reaction time on oddball tasks, even though it does not seem to benefit short term memory. It is possible that these cognitive modalities were negatively affected by simulated altitude, as evidenced by some altered event-related potentials, but that these effects were either too small to translate into performance deficits or that there are as yet unknown compensatory mechanisms at work that preserve performance as one ascends to altitude, at least until 3900 m.