Researchers have discovered neurons in mice that help their brains track and recover from sleep debt. If a similar pathway exists in humans, it could improve treatments for sleep disorders and other conditions marked by sleep impairment, such as Alzheimer’s disease.

We are all familiar with sleep debt, or the gap between how much sleep you need and how much you actually get. But until now, it wasn’t clear how the brain tracks sleep loss – or compels us to make up this difference.

at Johns Hopkins University in Maryland and his colleagues mapped brain pathways in mice that are involved in sleep by injecting a tracer into 11 brain areas known to induce sleep. The tracer, which travels from neurons receiving signals to those sending them, revealed 22 regions with connections to at least four sleep-promoting areas.

The researchers focused on a subset of 11 previously unidentified regions. Using a technique called chemogenetics, they gave mice specialised drugs that activate particular parts of their brains. They divided the mice into 11 groups of three to four individuals, activating a different area in each group.

A region called the thalamic nucleus reuniens seemed to be key. When neurons in this area were stimulated, the mice experienced the greatest increase in non-rapid eye movement (REM) sleep – about twice the amount as mice that weren’t stimulated. However, it took several hours for the animals to fall asleep after stimulation, during which they seemed to prepare for rest.

“When you go to bed, you probably brush your teeth, you wash your face, you fluff your pillow or arrange your blanket and then go to sleep,” says Wu. Mice do something similar. “They kind of groom their face, they clean their whiskers and then they fluff their nest up,” he says. This suggests these neurons aren’t an on-and-off switch for sleep – instead, they induce sleepiness.

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Another test also supported this idea. In six sleep-deprived mice, deactivating the thalamic nucleus reuniens brain cells made the rodents less sleepy – they were more active and spent less time nesting than control mice. They also got 10 per cent less non-REM sleep, on average.

Other experiments showed that these neurons activate during sleep deprivation and quiet down once sleep begins.

Together, the findings suggest this brain region drives sleepiness and triggers restorative sleep after sleep loss, says Wu. Developing therapies that target these neurons could lead to new treatments for hypersomnia – a sleep disorder characterised by excessive sleepiness after rest – as well as conditions such as Alzheimer’s disease, in which people don’t sleep enough.

However, it isn’t clear if the same brain circuit exists in humans, says at Stanford University in California. We also don’t know whether it plays a role in long-term sleep deprivation. “They’re focusing more on the short-term effects of sleep deprivation, which might not closely model humans with years and years and years of sleepless nights,” he says.

An obsessive approach to optimising sleep only tends to make things worse

It is no secret that sleeping is one of the most important things you can do for your health. Mountains of research over the past decade demonstrate, time and again, that a decent night’s rest is essential for everything from cognitive function to heart health, mood and more. Not getting good sleep or enough of it is associated with an increased risk of , type 2 diabetes, stroke, and hypertension, not to mention the hit to your .

For many of us, however, getting good sleep is often easier said than done. And much of the advice out there is probably familiar by now, if a little too generic: sleep for 8 hours, avoid bright light and anything stressful before bed, and so on.

In reality, life is messier. For a start, we don’t all need the same amount of sleep – our age, sex, personal habits and tolerances all influence what we individually need. We also all have different lifestyles, including work and travel, which might see us needing to adjust our sleep schedules on a regular basis. Getting good sleep is about more than just clocking up time spent in bed – but we also aren’t great judges of the quality of the sleep we, a consequence of being unconscious when doing the thing we are trying to assess.

All of this means that following prescriptive messages about sleeping more can feel frustrating. The good news, as we explore in this special issue devoted to the subject, is that new research is revealing the benefits of a more holistic approach – some of the most important things you can do to improve your sleep don’t happen in bed, no matter how comfortable that bed might be.

Your sleep is affected by what happens during the rest of the day, such as what and when you eat, as well as your gut microbiome and hormonal production. Your personal chronotype – not only when you prefer to sleep, but also when you’re most active during the day – plays a role in the quality and quantity of the sleep you get, too.

What we need, then, is a 24-hour perspective on sleep. None of this changes how crucial our unconscious hours are, but it does give us fresh opportunities to improve them well before we lay down our heads.

Explore key questions about sleep in our latest special series:

Why sleep quality is so important – and so difficult to measure

Sleeping a solid 8 hours isn't the whole story and the quality of your sleep might matter more. But what does sleep quality mean and how can we measure it?

Why your chronotype is key to figuring out how much sleep you need

Is 8 hours of sleep really the right amount for you? Understanding your personal chronotype could be a better way to approach how much time you should spend in bed

The surprising relationship between your microbiome and sleeping well

Research is revealing the complex relationship between sleep and the gut microbiome, raising the prospect that eating better during the day might help you get a better night’s rest

How best to catch up on rest and pay off your sleep debt

If you've missed out on sleep, it is possible to catch up. But is it better to try to do it all in one go or spread out over time – and is it really so bad to sleep in at the weekend?

How to shift your circadian clock to beat your jet lag

It is possible to speed up how quickly you get over jet lag – but calculating the right way to do it based on flight times, time zones and light exposure can be tricky

What nine sleep researchers do to get their best night’s rest

From carefully timing meals and bedtime to turning down the lights and banning screens in bed, here's what the scientists who study sleep do to optimise their slumber

A better understanding of our hormones and sleep could improve both

The hormonal changes of puberty, the menstrual cycle and menopause can all affect our sleep, but there are also subtler ways that hormones and sleep interact