Jet-setters and night owls will have felt the wrath of an off-kilter body clock, by way of the physical impact it can have on immediate well being. A yearning to understand the underlying reasons for this has been the subject of much scientific interest, and has led to some rather strange products like LED light glasses and glowing pillows. But by studying the biological clock of a humble fruit fly, researchers at Northwestern University are claiming to have uncovered the precise mechanisms that bring us in and out of sleep, with their evidence suggesting these switches date back hundreds of millions of years.

The Northwestern University scientists aren't the first to claim the discovery of a switch for the human biological clock. Earlier this year, a team from Tennessee's Vanderbilt University claimed to have found a way to change an animal's sleep and wake rhythms by stimulating neurons in the brain through a technique known as optogenetics. Last year, scientists from the University of Manchester did so by focusing on an enzyme known as casein kinase 1epsilon (CK1epsilon).

But what has led the Northwestern researchers to their discovery were studies carried out on the brain circadian neurons of an odd mutant fruit fly. They found that heightened sodium channel activity in brain circadian neurons during the daylight was waking up the fly, while high potassium channel activity at night was having the opposite effect.

Even more illuminating was the finding that mice rely on the same triggers, sodium and potassium currents, to move in and out of sleep cycles. This observation came about through a study of a small region of the mouse brain called the suprachiasmatic nucleus, made up of 20,000 neurons, where they found the same mechanisms working away. Mice are said to have almost identical biological clocks as humans, despite being nocturnal.

"This suggests the underlying mechanism controlling our sleep-wake cycle is ancient,” says Dr Ravi Allada, senior author of the study. "This oscillation mechanism appears to be conserved across several hundred million years of evolution. And if it’s in the mouse, it is likely in humans, too."

The researchers describe these ups and downs of the potassium and sodium levels as a "bicycle mechanism." This refers to the two pedals pumping up and down to keep the vehicle chugging along. They are now seeking to continue work in this area to learn more about what is regulating this sleep-wake pathway, which could led to the development of drugs that could potentially reset a person's internal clock to address sleep-wake issues related to jet lag, shift work and other problems.

The research was published in the journal Cell.