Auditory and Cognitive Functions during Heat Stress

Abstract

Excessive elevation of internal body temperature causes a significant strain on either the brain function or the locomotive system. Although hyperthermia impairs psychological and working memory performances, the effect of hyperthermia on cognitive processing remains unknown. We hypothesized that a passive heat stress impaired the cognitive function when the internal temperature was excessively increased. sixteen healthy males performed an auditory oddball paradigm before and after heat stress （Pre and Post） and when esophageal temperature was increased by 0.8 ℃ and 2.0 ℃ （Mild and Severe）．The reaction time and event-related potentials （ERPs） were recorded in these four sessions. As a countermeasure, subjects performed the same sessions without heat stress （i.e. normothermic condition）．The reaction time was shortened while esophageal temperature was elevated relative to the Pre but did not change in the normothermic trial. However the peak latency and amplitude of N100 component did not change throughout the experiment. Although the latency of P300 component was unaffected due to heat stress, the amplitude of P300 was significantly reduced at the Severe and Post relative to at the Pre. These results suggest that excessive elevation of internal temperature impairs cognitive processing but not auditory processing.