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It’s Only Human

Few researchers have studied the effects of electric lighting on the human body. At LRC, however, Assistant Professor Mariana Figueiro has broken new ground in this area, revealing crucial details about how the eye’s retina processes light and transmits that information into neural signals affecting our circadian system, which in turn links the body’s rhythms to daylight and darkness.


The Daysimeter measures exposure to circadian (short-wavelength) light.

Figueiro’s career is a testament to the interdisciplinary nature of research at LRC. She arrived at the center after earning an architectural engineering degree in her native Brazil and then obtained a master’s degree in lighting from LRC and a Ph.D. in multidisciplinary science from Rensselaer with her thesis work helping to uncover a phenomenon known as “subadditivity,” where more light can actually be less effective than less light of the right color. Natural sky-blue light, for instance, is ideal for stimulating the circadian system, helping to keep individuals alert during the day and resting at night. But exposure to some types of white light of the same intensity can be less effective. “The whole idea is to try to understand how the retina interprets light, and then apply and remove the right light at the right times to increase circadian rhythmicity. A breakdown in circadian rhythmicity will negatively affect sleep, health, and well-being,” Figueiro says.

Individuals with health challenges may benefit directly from this science. Alzheimer’s patients, for example, often have difficulty sleeping through the night, one reason they become institutionalized. “If you give the right light to Alzheimer’s patients during the day, you get an increased level of sleep efficiency at night,” Figueiro says. This suggests that nursing homes, rather than having generic designs, should be built in ways that will help alleviate troublesome conditions and symptoms for their residents.

This type of research could also help workers on night shifts, from doctors and nurses to law enforcement officers and air traffic controllers, perform better given the right kinds of exposure to light.

Figueiro describes her work in part as “a first attempt to bring some scientific validation to architectural practices.” That is, creating the right kind of functional design means connecting architecture and science. “If you understand the mechanisms and you really have an a priori hypothesis based on the physiology, that really narrows down a lot of the work.”

But Figueiro’s work also has widening possibilities, since her research interests a range of potential adapters from nursing homes to the Office of Naval Research, which is interested in the impact of light inside submarines.

LRC has built its success and reputation on interdisciplinary work that connects researchers from seemingly disparate fields. For example, LRC co-founders Rea, a biophysicist, and Leslie, an architect, still have offices next door to each other 20 years after the center opened. “Everybody’s a colleague, and everything is done in teams,” says Rea. “If you have an architect and a biophysicist working together, it’s a unique music you can create.”

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Rensselaer (ISSN 0898-1442) is published in Spring, Summer, Fall, and Winter by the Office of Strategic Communications and External Relations, Rensselaer Polytechnic Institute, Troy, NY 12180-3590. Opinions expressed in these pages do not necessarily reflect the views of the editors or the policies of the Institute. ©2008 Rensselaer Polytechnic Institute.