Time of day effects on cognitive processing and brain temperature.

摘要

Cognitive performance appears to vary as a function of the time of day in which the task is performed. This fluctuation in performance often is related to the circadian rhythm of body temperature. Fluctuations in cognitive performance have also been linked to changes in cerebral blood flow (as measured by brain temperature). This study was designed to determine whether task characteristics are differentially sensitive to time of day effects, resulting in differences in cognitive performance. Also, this study sought to determine if there is a time of day effect on the way in which brain temperature changes as a consequence of task performance. Tympanic membrane (TM) thermometry was used to measures changes in TM temperature while subjects performed a series of 4 cognitive tasks. TM temperature reflects average brain temperature and is an indirect measure of cerebral blood flow (CBF). Results showed that, as in previous studies, there is a time of day effect on body temperature. Only measures of short-term memory for word lists demonstrated a significant time of day effect. Results of this study indicate that CBF changes as a result of performing specific tasks. These changes in CBF are different at different times for the some tasks, even if there is no significant difference in performance. A significant interaction exists between the time of day in which a task is performed, the change in CBF, and the way in which the CBF changes. Implications for future time of day studies are discussed.