Mathematical Model Sheds New Light on Biological Clocks

November 12, 2009

A mathematical model developed by mathematicians at the University of Michigan has revolutionized our understanding of the human biological clock.

Located in a region of the central brain called the suprachiasmatic nuclei (SCN), the body's time-keeping mechanism controls sleeping rhythms and plays a role in disorders ranging from insomnia to Alzheimer's disease.

Previously, scientists believed that cells in the SCN regulated sleep pattern by firing rapidly during the day and slowly at night. The idea was that other organ systems took their cues from this tempo, speeding up or slowing down to match the SCN's electrical pulses. However, according to Michigan mathematician Daniel Forger, "the old model is, frankly, wrong."

The new model, designed by Forger along with graduate student Casey Diekman, shows that the majority of the time, even during the day, the SCN cells remain silent. They fire for a brief interval at dusk, and then again around dawn, serving as a sort of alarm rather than a constant metronome.

Data collected by a team of British scientists, led by Dr. Mino Belle and Hugh Piggins of the University of Manchester in England, corroborates Forger and Diekman's model. "This is a perfect example of how a mathematical model can make predictions that are completely at odds with the prevailing views yet, upon further experimentation, turn out to be dead-on," Forger said.

As enlightening as the findings are, they raise as many questions as they answer. As Piggins explained, the results "force us to completely reassess what we thought we knew about electrical activity in the brain's circadian clock."

The researchers published their findings, "Daily Electrical Silencing in the Mammalian Circadian Clock," in Science (Oct. 9, 2009).

Source: University of Michigan, Oct. 8, 1009.