Do You Really Need Sleep?

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The longer we go without sleep, the stronger the pressure to sleep grows. The reason for "sleep pressure" after going without sleep for an extended time, is a buildup of particular chemicals in specific parts of the brain.

Dr. Halassa says that the results of the new study show that "adenosine from astrocytes clearly regulates sleep pressure." He notes that this is the first time a non-neuronal cell within the brain has been shown to influence behavior. Unlike neurons, astrocytes do not fire electrical spikes, and they are often described as support cells.

In experiments on mice, Dr. Halassa and his colleagues used a genetic switch, called the dnSNARE transgene, to block the release of adenosine and other chemicals from astrocytes. The researchers then deprived the mice of sleep for short periods, and evaluated them with behavioral tests and with electroencephalography (EEG), a means of recording brain activity.

Mice subjected to the genetic blockade exhibited less sleep pressure than control mice. Following sleep deprivation, they did not need as much compensatory sleep, and during the early phases of sleep, they had patterns of brain activity consistent with low sleep pressure. When they were evaluated with a memory test, they performed as if their sleep had been undisturbed.

The researchers observed similar results when they used certain compounds to block the effects of adenosine on neurons. Neurons have several types of cell-surface receptors that enable them to respond to adenosine, but only pharmacological blockade of the A1 type of receptor was effective. That result shows that adenosine acts through the A1 receptor to produce sleep pressure. _MNT

These results hint that most humans may not need to sleep as much as they do. If new drugs can influence sleep pressure by acting through the A1 receptors of neurons in the VLPO sleep-inducing area of the brain without serious adverse effects, humans in a wide range of professions and vocations might be able to perform to a higher standard.

Only further research can tell whether other problems -- such as memory loss or behavioural instability -- may occur despite the absence of sleep pressure, when extended sleep deprivation is induced. Eventually the brain centers responsible for maintaining attention and vigilance would presumably "run down" and require replenishment. Controlled experiments should tell us how long the sleepless period can be safely extended.

Since several other brain areas besides the VLPO are involved in control of sleep, it is inevitable that eventually the brain will run into a brick wall of some type, without sleep. It will take time and work to find all the answers, but for now sleep scientists have a solid theory to work with.