Relationship between alertness, performance, and body temperature in humans

ture has been reported to influence human performance. Performance is reported to be better when body temperature is high/near its circadian peak and worse when body temper-ature is low/near its circadian minimum. We assessed whether this relationship between performance and body temperature reflects the regulation of both the internal bio-logical timekeeping system and/or the influence of body tem-perature on performance independent of circadian phase. Fourteen subjects participated in a forced desynchrony pro-tocol allowing assessment of the relationship between body temperature and performance while controlling for circadian phase and hours awake. Most neurobehavioral measures varied as a function of internal biological time and duration of wakefulness. A number of performance measures were better when body temperature was elevated, including work-ing memory, subjective alertness, visual attention, and the slowest 10 % of reaction times. These findings demonstrate that an increased body temperature, associated with and independent of internal biological time, is correlated with improved performance and alertness. These results support the hypothesis that body temperature modulates neurobe-havioral function in humans. sleep homeostasis; circadian phase; neurobehavioral perfor-mance; forced desynchrony; core body temperature CONSIDERABLE EFFORT has been devoted to understand-ing the relationship between body temperature an