U-M Ann Arbor mathematicians research on biological clock. According to the mathematicians, the clock that determines and controls our biological rhythms that tell whether we are a day or night person is not ticking the way that scientists have long believed.

Our biological clockis located in the central brain region called suprachiasmatic nuclei. For so many years, scientists have believed the clock time is determined by the speed at which the cells fire their electrical pulses — fast during the day, slow at night.

The clock plays a role in cell division, heartbeat rates and many other biological functions. For those who have experienced jet lag or a sleep disorder, you just know how bad it feels when you are not in sync with your surroundings. If you are going to treat diseases such as cancer, it is very important that you understand your clock. Chemotherapy drugs are injected at a certain time when doctors thought that they are dividing most rapidly.

According to the new research which was published in the current issue of the journal Science, researchers developed a mathematical model showing that the suprachiasmatic nuclei cells don’t fire faster during the day and slower during the night, as had been assumed. Instead, the model shows that the cells would only fire in brief bursts a couple of times in a 24-hour cycle.

The Michigan mathematicians together with scientists from the University of Manchester in the U.K., examined mice and found that the suprachiasmatic nuclei cells remained in an electrically excited state during the day, but did not fire. Around dusk, the cells would fire for a brief period and then they go quiet again. There is another burst when dawn comes.

The findings “force us to completely reassess what we thought we knew about electrical activity in the brain’s circadian clock,” according to Manchester’s Hugh Piggins. Although this research raises the question whether the biological clock works in an analog or digital manner, it does not provide an answer.

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