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Troy, N.Y. -  10/18/2005

Framework Developed for Testing How Lighting Can Affect Human Health

New scientific model will be featured in Brain Research Reviews

Scientists at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute have taken a significant step forward in understanding how light affects the human body. The scientists developed a model that postulates the mechanisms by which humans process light for the circadian system, the body's system that regulates rhythms such as body temperature, hormone production, alertness, and sleep patterns. The research will be featured in Brain Research Reviews.

The "circadian phototransduction" model offers a framework for testing and exploring the practical aspects of architectural lighting and how it can affect human health. "The model is important in two ways," said Dr. Mark Rea, director of the LRC and lead researcher on the project. "It is theoretically important for generating hypotheses about neural mechanisms; and it is practically important for predicting the relative effectiveness of different light sources for impacting the human circadian system."

Rea says the model can be used as the foundation for a new system of circadian photometry, the study of how light affects the circadian system, much like the current system of photometry based on human vision. Quantification of light as a stimulus for the circadian system has profound implications for exploring how lighting can be used to adjust our bodies' internal clocks. "The model takes into account the high sensitivity of the human circadian system to short-wavelength (blue) light," explained Rea. "But it also considers evidence for a phenomenon known as spectral opponency. When middle-wavelength (yellow) light is added to short-wavelength light, the resulting white light is actually less effective at regulating the circadian system."

According to LRC researchers, the model is based on recently published evidence from electrophysiology and neuroanatomy. It incorporates newly-discovered retinal neurons that respond directly to light exposure called intrinsically-photosensitive retinal ganglion cells, or ipRGCs, as well as traditional photoreceptors (rods and cones).

LRC scientists plan to extend and refine the circadian phototransduction model, as well as bridge the findings to practical applications.

The research is summarized in a paper titled, "A model of phototransduction by the human circadian system," available in the Brain Research Reviews journal online and will be published in an upcoming print edition of the journal.

About the Lighting Research Center
The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute is the world's leading center for lighting research and education. Established in 1988 by the New York State Energy Research and Development Authority (NYSERDA), the LRC conducts research in light and human health, transportation lighting and safety, solid-state lighting, energy efficiency, and plant health. LRC lighting scientists with multidisciplinary expertise in research, technology, design, and human factors, collaborate with a global network of leading manufacturers and government agencies, developing innovative lighting solutions for projects that range from the Boeing 787 Dreamliner to U.S. Navy submarines to hospital neonatal intensive-care units. In 1990, the LRC became the first university research center to offer graduate degrees in lighting and today, offers a M.S. in lighting and a Ph.D. to educate future leaders in lighting. Learn more at

About Rensselaer Polytechnic Institute
Founded in 1824, Rensselaer Polytechnic Institute is America's first technological research university. Rensselaer encompasses five schools, 32 research centers, more than 145 academic programs, and a dynamic community made up of more than 7,900 students and more than 100,000 living alumni. Rensselaer faculty and alumni include more than 145 National Academy members, six members of the National Inventors Hall of Fame, six National Medal of Technology winners, five National Medal of Science winners, and a Nobel Prize winner in Physics. With nearly 200 years of experience advancing scientific and technological knowledge, Rensselaer remains focused on addressing global challenges with a spirit of ingenuity and collaboration.