Abstract
Some animals have mechanisms that selectively cool the brain during hyperthermia. However, it remains controversial if humans have the mechanism. In the present study, we investigated the effect of the head or neck cooling on tympanic temperature as an indicator of brain temperature in normothermic and hyperthermic conditions. Eight healthy male subjects performed four local cooling trials (facial fanning, cooling of the forehead and neck, and the control). Subjects sat on a chair, putting on a water‐perfusion suit to maintain skin temperature at 33°C (normothermic condition) or 38°C (hyperthermic condition). Tympanic, esophageal, and skin temperatures were continuously monitored. Temperature sensation and thermal pleasantness were reported by the subjects. After 10‐min baseline period, local cooling was conducted for 15 min. During the head or neck cooling, the local skin temperature significantly decreased, however, there was no significant difference between tympanic and esophageal temperatures in normothemic condition. Only in hyperthermic condition, a significant difference between tympanic and esophageal temperatures was observed. After facial fanning, tympanic temperature was lower than esophageal temperature. While facial fanning produced a slight change in thermal pleasantness in normothermic condition, facial fanning produced a clear “pleasant” feeling in hyperthermic condition. These results may suggest that facial fanning cools the brain in hyperthermic condition. However, local skin cooling of the forehead and neck may not effect on the selective brain cooling.Grant Funding Source: This study was supported by JSPS KAKENHI Grant Number 25870831
Published Version
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