It is a truism that, while we can stare deeply out into the cosmos, the interiors of our own Planet’s oceans remain mysterious and largely unexplored. Equally, while psychology and neuroscience have constructed complex models to explain the workings of the brain, sleep is a neural abyss which remains persistently enigmatic.
The waters we fall into every night are as mysterious as the rifts of the Indian Ocean. A healthy person sleeps seven hours out of every twenty four: that’s nearly a third of a lifetime. The conscious functions of the brain switch off and rest. We go through cycles of mental regeneration. We dream. Whatever constitutes consciousness ceases temporarily to exist before returning, along with our sense of identity, in the morning. Because the normal experience of existence is absent from sleep, it is difficult to draw conclusions as to what sleep actually is: attempting to make sense of an altered state of consciousness is like trying to remember a dream. At this point, scientists are only beginning to make inroads into the vast and trackless reaches of this subject, attempting to understand how sleep works, what it does, and what its purpose is.
Evolutionarily it makes little sense to leave yourself unaware and defenceless for a third of the day, so sleep couldn’t exist unless it was vital. Experiments in sleep deprivation have borne this out, with participants swiftly degenerating into mental collapse after too long without catching some ZZZs.
Insomnia a modern puzzle
Insomnia, the inability to fall asleep, plagues the modern world, often exacerbated by factors such as long working hours, artificially lit cities, caffeine, and other stimulants, which can offset or disrupt the instinctive process of falling asleep. While it is possible to induce sleep through the use of tranquilisers, these often have unwanted side effects and are not necessarily conducive to truly healthy sleep. Therefore, the search continues for more effective treatments for insomnia, necessitating a greater clinical understanding of the neural mechanisms controlling sleep itself.
Further to this, a ‘sleep switch’ in the brain, discovered recently by scientists at Oxford University, has been heralded as a potential breakthrough in the development of better sleeping pills. Dubbed ‘Sandman’ the switch is triggered by falling levels of the neurotransmitter dopamine which is known to keep people awake. The scientists involved have been trying to work out how the brain suddenly switches off in sleep, a process which has widespread effects throughout the brain.
Sleep is governed by two system: the circadian clock which monitors the time of day, and a mechanism called the ‘sleep homeostat’ which can trigger sleepiness even when it is not dark.
"The circadian clock allows us to anticipate predictable changes in our environment that are caused by the Earth’s rotation," said lead author Professor Gero Miesenböck.
"As such, it makes sure we do our sleeping when it hurts us least, but it doesn’t speak to the mystery of why we need to sleep in the first place. That explanation will likely come from understanding the second controller—called the sleep homeostat.The homeostat measures something—and we don’t know what that something is—that happens in our brains while we are awake, and when that something hits a certain ceiling, we go to sleep. The system is reset during sleep, and the cycle begins anew when we wake up."
The team studied the sleep homeostat in the brains of fruit flies which are thought to have the same sleep-control neurons as humans. If the sleep-neurons are electrically active, the fly is asleep, and when they are silent, the fly is awake.
Researchers found that the sleep-control neurons are either on or off based on the activity of the ‘Sandman’ switch, a physical gate which allows or blocks electrical signals to the cells. When dopamine production stops, the switch is flicked and sleep is triggered. Finding a drug to trigger the Sandman switch could help insomniacs. Scientists think that making a drug to flick the switch could create a new generation of super-efficient sleeping pills.
“If human cells have a similar switch, Sandman could become a very clean and very efficient sleeping pill,” added Professor Miesenböck. “It would be a very quick way of getting to sleep for someone suffering from insomnia.”
As human technology continues to progress, there is a danger that our own natures will conflict with the systems that we produce to live in and around. Simultaneously, as our understanding of ourselves increases through the use of science, more and more of the mysterious mechanisms of life will potentially come under our control.
As Professor Miesenböck says: “Sleep is still one of the mysteries. It creates considerable risks to disconnect yourself for seven to eight hours every day. Our long term goal is to find out what sleep is for and try and control it”.
The Oxford University research was published in the journal Nature.