Special Mathematics Department Colloquium Daniel Forger Courant Institute, NYU "Math Matters in Biological Timekeeping" Wednesday January 12, 2005 3:45pm in JWB 335 Biological clocks with a period near one day (circadian) are essential for the survival of most organisms. Circadian clock disorders in man can lead to poor productivity, jet lag, sleep disorders and have been linked to Alzheimer's disease and cancer. The circadian clock within a cell is comprised of a feedback network of genes and proteins. In man, a group of about 20,000 neurons in the brain (the suprachiasmatic nucleus, SCN), many of which have an internal circadian clock, form our central circadian pacemaker and regulate our sleep-wake patterns, core body temperature and the release of most hormones in the body. The first half of the talk will describe a detailed mathematical model of circadian clock in SCN neurons I have developed with Charles Peskin. I will then briefly outline how simulations of this model, and mathematical analysis can used to understand key questions in circadian biology including: 1) How intracellular clocks function accurately despite the inherent stochasticity of the molecular interactions of which they are comprised and 2) How intracellular clocks keep an approximately 24-hour period over a wide range of temperatures. If time permits, I will also discuss: 1) Mathematically predicted biological mechanisms which cause oscillations in genetic feedback loops, and 2) How mathematical models of circadian clocks can help you work productively and avoid jet lag.