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Current Projects: Air Force Office of Scientific Research
Title: Effects of Cognitive Task Difficulty on Sleep-Wake Homeostasis
Principal Investigator: David F. Dinges, Ph.D.
Air Force operations place a high value on cognitive performance capability around the clock, but jet lag, night work and sleep loss can markedly erode this capability. Accurate understanding and prediction of cognitive performance impairment during such fatiguing conditions is critical to effectively managing fatigue and the risks it poses for errors and accidents. Despite a belief in operational communities that the nature of cognitive work performed - especially cognitive task difficulty - during sleep loss can influence the magnitude of the fatigue response and recovery from it, current practical, theoretical and mathematical models of cognitive performance during sleep deprivation ignore this factor. In other words, these models assume that sleep loss adversely affects cognitive activity, but cognitive activity has no affect on sleepiness or sleep. However, we have preliminary evidence suggesting that cognitive workload can potentiate the effects of sleep loss and further degrade performance, especially vigilant attention performance, which is fundamental to many safety-sensitive tasks in Air Force operations.
The objective of this proposal is to expressly evaluate the possibility that cognitive task difficulty from increased demands on attention will interact with sleep loss and produce objective evidence of changes in sleep-wake responses. Thus, we will undertake the first systematic scientific evaluation of the effects of increasing cognitive task difficulty on sleep-wake homeostasis by varying attentional task difficulty with a working memory paradigm embedded in the PVT vigilant attention task. Using a within-subjects design and an 11-day laboratory protocol, we will study 36 healthy adults subjects (ages 21-45 yr) at three levels of attentional task difficulty in both rested and sleep-deprived conditions, to determine the effects of task difficulty on (1) the waking ability to avoid performance lapses and the ability to resist sleep, as well as other behavioral and physiological markers of sleepiness and fatigue; (2) physiological sleep responses, especially those associated with homeostatic sleep drive, such as NREM EEG slow-wave activity; and (3) cerebral blood flow (CBF), using the new technique of arterial spin labeling perfusion functional magnetic resonance imaging (fMRI) to measure absolute CBF as a function of task difficulty, sleep deprivation and the interaction of these factors.
As the first systematic scientific evaluation of the effects of cognitive task difficulty on sleep-wake homeostasis, the experiment will break new ground advancing the understanding of cognitive performance during sleep loss. It will resolve the question of whether or not there are cognitive use-dependent effects on sleep and waking brain physiology and behavior via the attention system. It will specifically determine whether cognitive task difficulty manipulated via the attention system interacts with sleep deprivation to influence the magnitude of the fatigue response and recovery from it during sleep. If evidence is found for cognitive use-dependent effects on aspects of sleep-wake homeostasis, it will have significant implications for theories and models of cognitive function, attention and arousal, fatigue and performance, sleep-wake regulation and the functions of sleep. The research also has a high potential for important advances in identifying the brain mechanisms subserving attention and arousal and their interaction in rested and fatigued states, through use of arterial spin labeling perfusion fMRI, which unlike other fMRI approaches measures absolute CBF levels with excellent reproducibility, greater functional sensitivity contrast, better detection of differences in regional brain activation over time, and superior power in group analysis. This will be the first application of the technique to the study of cognitive performance and sleep deprivation. Overall, the research is scientifically and technologically cutting edge, with a high likelihood of leading to consequential new discoveries relevant to both the advancement of basic science and Air Force needs.
Links:
Air Force Office of Scientific Research - http://www.afosr.af.mil/