1 March 2006
Sleep:
What Happens When Doctors Do Without It?
Charles Czeisler, Ph.D., M.D., Division of Sleep Medicine
Brigham and Women's Hospital and Harvard Medical School
Irving L. Kron, M.D., Department of Surgery, UVA
What do we know now of the neurobiology of human sleep and the behavioral consequences in persons who experience sleep disturbances or sleep deprivation? How is the science of sleep influencing the ways human activity is regulated, including the determination of duty-hour limits for physicians in training?
Dr. Czeisler’s research focuses on understanding the neurobiology of the human circadian pacemaker, located in the suprachiasmatic nuclei (SCN) of the hypothalamus, and applying that knowledge to clinical medicine and occupational health. His Division's earliest work revealed that sleep duration and structure was regulated by the output of this pacemaker. Since then, his Division unmasked the endogenous circadian component of various neuroendocrine, metabolic, thermoregulatory and behavioral rhythms controlled by the pacemaker, by studying human subjects under constant environmental and behavioral conditions.
His current research focuses on four main areas: The first is the neurobiology of circadian photoreception in humans. His Division has shown that among human subjects who completely lack conscious visual perception, there are a subset who retain normal circadian responsiveness to light. This response is mediated through the eyes and persists even in some subjects who have severe retinal degeneration. He is investigating the influence of light intensity, duration, timing and wavelength on circadian entrainment. The second involves evaluation of how circadian and homeostatic processes interact to regulate sleep and neurobiological function during wakefulness. The third is the examination of the role of melatonin in the organization of sleep and circadian rhythms. Melatonin is typically secreted in a circadian manner by the pineal gland, which is controlled by the SCN via a circuitous neural peripheral pathway. Other ongoing research in his lab includes functional magnetic imaging, quantitative analysis of sleep and waking EEG, and the influence of sleep loss on the deployment of visual attention.