It may one day be possible to reap some of the benefits of sleep without ever closing our eyes. Stimulating specific brain activity in awake mice led to some of the same effects as deep sleep, including a boost in memory.

“It should be possible, at least in theory and to some extent, to replicate these results in our species,” says at the University of Oxford, who wasn’t involved in the research. “It would be fascinating to explore whether artificially inducing [this activity] during waking [hours] in humans can result in a subjective feeling of being more refreshed and rested afterwards.”

Sleep is thought to be an essential way for the brain to carry out most of its maintenance work. This includes synaptic homeostasis, the process whereby the brain declutters the thousands of new neural connections made during the day – storing important ones and weakening or cutting away ones that aren’t as necessary.

During non-rapid eye movement (NREM) sleep – the deep sleep state that makes up around 80 per cent of sleep in adults – the brain’s cortex repeatedly fires signals at the exact same time and then shuts those neurons off, in a pattern called slow-wave sleep activity. “This has been linked to synaptic homeostasis, and may be a key mechanism underlying sleep’s restorative functions,” says at the University of Wisconsin-Madison.

Cirelli and her colleagues wondered if a small part of the cortex could be nudged into entering this deep sleep state while an individual is still awake. Some animals do this naturally, such as dolphins, ducks and fur seals, in which one half of the brain enters NREM sleep while the other remains alert and vigilant for predators.

To see if a similar state could be induced, the researchers genetically engineered mice so their neuronal activity could be switched off using light. They implanted a probe into one half of their brain and kept the mice awake for five hours by giving them new things to explore. Near the end of this time period, the light probe was repeatedly turned on and off for 30 minutes, mimicking NREM sleep.

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Afterwards, when the mice were allowed to sleep, brain recordings showed that the stimulated side of the brain didn’t show the usual signs of exhaustion caused by sleep deprivation. “Because that small part of the brain did its decluttering while awake, it no longer needed extra deep sleep afterwards,” says Cirelli.

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Next, the researchers wondered whether forcing sleep during wakefulness boosts memory. So they placed the genetically modified mice in a square box with carpet that had the same texture on both sides of the container. After 15 minutes of exploring the space, the mice were assigned to either a sleep group, a group that was sleep-deprived for 1 hour, or a group that was sleep-deprived for 1 hour but received the artificial deep-sleep stimulation.

The next day, the mice went back into the box, but one side of the container had a new texture. Mice are naturally drawn to novelty, so the researchers measured how much they remembered the old environment by the amount of time they spent on the new side. They found that the sleep-deprived mice that received no stimulation seemed to struggle to tell the new and old side apart, while both the sleep group and the sleep-deprived mice that received the stimulation spent more time on the new side.

The team plans to study whether similar effects could come about in people if this brain activity were induced non-invasively via transcranial electrical stimulation. However, Vyazovskiy stresses that sleep can probably never be replaced. “Sleep is of two kinds – NREM and REM [rapid eye movement] – and we still do not know what it is about the alternation of these two states that makes sleep complete,” he says.

This article appeared in print under the headline “Hog in the limelight”

Donut eat them (Image: Roy Ooms/Getty)

Here’s something to chew over. Eating more trans fats is linked to coronary heart disease, while eating saturated fats is not. That’s according to an analysis of 123 studies of dietary fat and cardiovascular health.

Most dietary advice recommends limiting the consumption of saturated fats, which are found in butter, milk, meat and egg, due to the risk of developing heart disease. But Russell de Souza of McMaster University in Ontario, Canada, and his team were unable to find a clear association between these fats and the chances of heart or cardiovascular disease.

This wasn’t the case with industrial trans fats, which are made by hydrogenating plant oils and are found in margarine and some processed foods like cake. The analysis suggests that eating more trans fat is associated with a 21 per cent rise in the likelihood of developing heart disease, and a 28 per cent rise in the risk of dying of this condition, confirming a number of other reviews that have linked trans fats to heart disease.

Earlier this year, the US Food and Drug Administration banned the use of trans fats in food, giving manufacturers three years to comply.

“The results of this review support existing guidance to avoid industrially produced trans fats,” said Victoria Taylor, a dietician for the British Heart Foundation charity. “In the UK, industry action to remove these fats from manufactured foods means that our intakes are already below the recommended maximum of 2 per cent of food energy.”

The UK also advises that saturated fat makes up no more than of a person’s daily energy intake.

But de Souza’s results don’t necessarily mean it’s time to scrap this recommendation just yet. Although they were unable to find a link in their analysis, it is still possible that there might be one. Furthermore, sources of saturated fat may pose other health risks, says de Souza.

“There are many factors which cause coronary heart disease and no single food or nutrient is solely responsible for this,” said Taylor. “We will continue to recommend switching saturated fat for unsaturated fat, consistent with a traditional Mediterranean-style diet.”

Journal reference: BMJ, .

(Image: Kevin Schafer)

Fancy a bite to eat? This pink river dolphin is skilfully snatching a snack but the animal can itself be a controversial source of food.

Found in the Amazon and Orinoco rivers, the river dolphins, also known as boto, are endangered due to pollution, boat accidents and habitat loss. Far worse, however, was their use by the fishing industry as bait to catch catfish, later sold in Brazilian markets.

Brazilians aren’t fond of eating catfish, considering it to be repulsive. But they were perhaps tempted to try a fish called “douradinha” that suddenly appeared in markets about seven years ago.

When the fish couldn’t be matched to any known Amazonian species, Haydée Cunha at the Rio de Janeiro State University and her team decided to investigate. Sixty-two “douradinha” samples were purchased for DNA sequencing. The analysis showed that 60 per cent of the samples were in fact catfish, while the rest were other fish species of low commercial value. When the stomach contents from two samples, which were actually catfish, were analysed, river dolphin was present suggesting it had been used as bait.

Thanks in part to the genetic detective work, the catfish fishery was banned in Brazil last year. Further details of the analysis have now been published to highlight the growing use of DNA techniques for conservation in Latin America.

Last year, a new species of river dolphin was discovered for the first time in a century.

Journal reference: