The effect of hyperthermia on cognitive and auditory processing

Abstract

Hyperthermia is thought to cause a significant strain on either the brain function or the locomotive system. In fact, hyperthermia impairs psychological and working memory performances, but the effect of hyperthermia on either cognitive or auditory processing remains unknown. We hypothesized that a passive heat stress impairs the cognitive function when the internal temperature was excessively increased. Thirteen healthy males performed an auditory oddball paradigm before and after heat stress (Pre and Post) and when esophageal temperature was increased by 0.8 °C and 2.0 °C (Mild and Severe). The reaction time and event‐related potentials (ERPs) were recorded in these four sessions. As a time control, subjects performed the same sessions without heat stress. The reaction time was shortened while esophageal temperature was elevated relative to the Pre but did not change in the time control trial. However the peak latency and amplitude of N100, indicated auditory processing, did not change throughout the experiment. Although the latency of P300 was unaffected due to heat stress, the amplitude of P300, indicated cognitive processing, was significantly reduced at the Severe (10.5±5.9 μV) and Post (11.1±5.5 μV) relative to at the Pre (16.3±4.7 μV). These results suggest that excessive elevation of internal temperature impairs cognitive processing but not auditory processing.