George C. Brainard has directed Jefferson's Light Research Program since 1984. This program's research studies the effects of light on neuroendocrine physiology and circadian regulation in humans. Using the techniques of photobiology, radioimmunoassay, and performance testing, this group has documented how various visible and nonvisible light sources influence both hormonal balance and behavior. Current studies include elucidating the action spectrum of melatonin regulation, investigating the phase shifting capacities of light, studying the influence of light on tumor progression, and testing new light treatment devices for winter depression.