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Principal Investigator:
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Derk-Jan Dijk, Ph.D.
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Organization:
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Harvard - Brigham and Women's Hospital
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Project Ended:
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1999
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Total sleep deprivation leads to decrements in eurobehavioral performance and changes in electroencephalographic (EEG) oscillations as well as the incidence of slow eye movements detected in the electro-oculogram (EOG) during wakefulness. Although total sleep deprivation is a powerful tool to investigate the association of EEG/EOG and neurobehavioral decrements, sleep loss during space flight is usually only partial. Furthermore, exposure to the microgravity environment leads to changes in sodium and volume homeostasis and associated renal and cardio-endocrine responses. Some of these changes can be induced in head-down tilt bed-rest studies. We integrate research tools and research projects to enhance the fidelity of the simulated conditions of space flight which are characterized by complex and mutual interactions. The effectiveness of countermeasures and physiologic mechanisms underlying neurobehavioral changes and renal-cardio endocrine changes are investigated in projects of the Human Performance Factors and Cardiovascular Alterations teams. Although the specific aims of these two projects are very different, they employ very similar research protocols. Thus, both projects investigate the effects of posture/bedrest and sleep deprivation (total or partial) on outcome measures relevant to their specific aims. The main aim of this enhancement grant is to exploit the similarities in research protocols by including the assessment of outcome variables relevant to the Renal-Cardio project in the research protocol of Human Performance Factors project and by including the assessment of outcome variables relevant to the Quantitative EEG and Sleep Deprivation Project in the research protocols of the Cardiovascular Alterations project. In particular we will assess neurobehavioral function and waking EEG in the research protocols of the renal-cardio endocrine project and renin-angiotensin and cardiac function in the research protocol of the quantitative EEG and waking neurobehavioral function project. This will allow us to investigate two additional specific aims:
1) Test the hypothesis that chronic partial sleep deprivation during a 17-day bed-rest experiment results in deterioration of neurobehavioral function during waking and increases in EEG power density in the theta frequencies, especially in frontal areas of the brain, as well as the nonREM-REM cycle dependent modulation of heart-rate variability.
2) Test the hypothesis that acute total sleep deprivation modifies the circadian rhythm of the renin-angiotensin system, changes the acute responsiveness of this system to posture beyond what a microgravity environment alone does and affects the nonREM-REM cycle dependent modulation of heart-rate variability.
The data obtained on the waking EEG and neurobehavioral function in the chronic partial sleep deprivation experiment will complement the data obtained on the effects of total sleep deprivation which are collected in the Human Performance Factors project. The data obtained on the renin-angiotensin levels in the acute total sleep deprivation experiment will complement data obtained on the effects of chronic partial sleep deprivation which will be collected in the Cardiovascular Alterations project. We have obtained recordings in two subjects who participated in a 24-day laboratory study with 21 days of continuous bedrest. The application of identical research tools and outcome measures in research protocols across the Cardiovascular Alterations and Human Performance Factors team will greatly enhance the overall science return of these projects and emphasizes the synergistic nature of this application.
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