The body synchronizes its sleep-wake cycle to the Earth’s light-dark cycle, and disruption of this synchronization can result in chronic sleep loss. Dr. Fred W. Turek is studying circadian disruption and sleep loss in mice to explore the interactions between circadian rhythm and sleep. This research should provide information needed to develop countermeasures against circadian rhythm disruption experienced by astronauts in space and by night-shift workers or international travelers on Earth.
Overview
Animal Model for Sleep Loss and Circadian Disruption
Principal Investigator:
Fred W. Turek, Ph.D.
Organization:
Northwestern University
Technical Summary
The adverse effects associated with imposed disruptions of the normal circadian and sleep-wake cycles are particularly relevant to NASA personnel and their ability to carry out normal duties at a high level of efficiency. Many space travel situations demand that both ground-based and flight personnel engage in duty schedules that can lead to circadian rhythm disruption and sleep loss. The tasks that can be affected involve vigilance, operation and control of vehicles/aircraft, maintenance, preparation and operation of equipment as well as command and control activities. Night operations are important for successful missions, and there is a clear need to find countermeasures that can alleviate the adverse effects of these activities on human circadian rhythms and sleep as well as on neurobehavioral capabilities and on physical performance.
Despite the high prevalence of chronic partial sleep loss and circadian disruption due to shiftwork in modern society, no animal models have previously been developed to systematically examine the effects of chronic partial sleep and circadian disruption on sleep architecture and performance. The use of a new animal model, as outlined in the original proposal, will lead to new insights into how the circadian and sleep systems are affected by the disruption of their normal phase relationship to one another, and how this temporal disorganization influences neurobehavioral capabilities and motor performance. Information gained using this novel animal model will also be important in the development of effective countermeasures to the adverse effects associated with circadian disruption and sleep loss. These countermeasures could be useful in a number of situations involving NASA personnel, particularly in extended duration space flight missions that will result in challenges to the sleep and circadian system of the flight crew and support teams. This project will also provide important insights in to the interactions between the circadian and sleep/wake systems.
Specific Aims
There are three specific aims of the project: 1) to determine the effects of 12 hours of imposed wakefulness during both normal active and inactive periods on circadian rhythms, the sleep-wake cycle and neurobehavioral and motor performance measurements, 2) to test the hypothesis that treatment with either a physiological or pharmacological dose of melatonin at the beginning of the imposed period of wakefulness will alter the effects of this temporal desynchrony on the circadian clock, the sleep-wake cycle, and/or on neurobehavioral and motor performance measurements and, 3) to test the hypothesis that access to a wheel (exercise) when in the home cage will alter the effects of the imposed periods of wakefulness on the circadian clock, the sleep-wake cycle, and/or neurobehavioral and motor performance measurements.
During the award period we have examined the impact of chronic partial sleep loss and circadian disruption on sleep, circadian rhythms and neurobehavioral and motor performance. With the development of an animal model of sleep loss and circadian disruption, we have determined that mice respond in a similar way to chronic partial sleep loss and circadian disruption as humans. Sleep is altered depending on the strain and the time-of-day of sleep restriction. During our forced wakefulness procedure animals are not able to get any REM sleep but can get anywhere between 5 to 40 % NREM sleep. Over the 10 day period of partial sleep restriction animals are sleep deprived of between 26 to 41 hours of sleep, depending on the strain and time of sleep restriction (i.e. light or dark period). The degree of sleep loss seen in these studies is equivalent to a human obtaining approximately 5-6 hours of sleep per night, which is commonly seen on shuttle missions. We have also determined that this moderate degree of sleep deprivation does not significantly impair performance on a task of neurobehavioral and motor performance. The data collected during this unique study appears to be similar to data recently published on human subjects exposed to chronic partial sleep loss.
This project's funding ended in 2004