A cognitive “speed training” game that cuts dementia risk by 25 per cent alters levels of beta-amyloid, a protein that clogs up the brain in Alzheimer’s disease, in men, but not in women.

It is the first time brain training has been shown to influence the levels of a neurodegenerative marker, strengthening the evidence suggesting that mental exercises can boost brain health.

“One of the main markers that’s indicative of future dementia risk got better for men who completed cognitive speed training,” says  at Clemson University in South Carolina, who presented the research at the Alzheimer’s Association International Conference in London on 12 July.

The computer-based speed training involves recalling where objects have flashed up, with the task becoming harder as performance improves. A prior 20-year study by some of Chai’s colleagues showed that people aged 65 and older, who did the training were 25 per cent less likely to be diagnosed with Alzheimer’s disease or a related form of dementia compared with a control group.

In the latest study, Chai and her team recruited a separate group of 53 people from the US aged 65 and older, 13 of whom were male. About a third of the participants were asked to complete between 2 and 4 hours of speed training each week for 4.5 months.

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The remaining participants were either told to spend the same amount of time playing games such as Solitaire, word search and a game similar to Connect 4, or to complete another kind of brain training in which they had to strategically track objects and switch between tasks.

To explore how speed training may reduce dementia risk, the team collected blood samples from all of the participants at the start and end of the training period.

This revealed that, among men, speed training increased the ratio of two forms of beta-amyloid found in the blood, which suggests the training boosted the brain’s ability to clear beta-amyloid 42. This protein forms clumps called plaques in the brain during Alzheimer’s disease, disrupting brain function. The other two kinds of training had no effect.

“It’s a really cool finding,” says  at McGill University in Montreal. “It is definitely strengthening what they’ve [previously] shown with the reduction in dementia.”

Some Alzheimer’s treatments, such as lecanemab, have been designed to help clear amyloid from the brain, but they only marginally slow cognitive decline during Alzheimer’s disease. The limited benefit seen in trials is probably down to these treatments being taken at a relatively late stage of the condition, when substantial brain damage has already occurred, says at University College London.

Engaging in cognitive training to reduce beta-amyloid build-up before dementia develops may have a bigger effect on dementia because it would be done before much brain damage has occurred, says Castegnaro.

However, cognitive training had no effect on amyloid levels in female participants in the study. This suggests that speed training reduces dementia risk in different ways in women and men, says Chai.

The team hopes to explore how speed training may benefit women in future studies, says Chai. But first, the findings need to be verified in geographically and ethnically diverse groups, says Novozhilova.

Global warming-fuelled heat and drought is already hitting yields of maize, wheat and soybeans to the tune of $20 billion a year, a study has estimated. This could rise eightfold, to more than $160 billion by 2100, unless we slash emissions.

While the financial losses will be greatest for big producers such as the US, the impacts will be felt most in the lowest-income countries, where ,��������� at the International Institute for Applied Systems Analysis (IIASA) in Austria. “If you look at the least-developed countries in Africa, the impact is much bigger.” This could lead to social unrest and increased migration, she warns.

There is great uncertainty about these kinds of projections, not least because so much depends on how farmers respond and adapt to a continually changing climate, for instance, by switching to different crops or adopting irrigation where it is possible. In fact, the whole point of this study is to raise awareness and encourage adaptation, to help ensure these projections turn out to be overestimates, says team member , also at IIASA. “This is the entire mission of climate scientists: we make these cases for people to react, so our projections turn out to be wrong.”

The researchers started by gathering data on the yields per country of maize, wheat and soya from the UN Food and Agriculture Organization (FAO). Next, they took past climate data and calculated the drought level, using a standard approach that estimates soil moisture levels from rainfall and evaporation levels.

Past heat extremes and drought levels were then compared with the yields from 1974 to 2004 to estimate the impact of heat and drought. They then used these statistical correlations to estimate crop losses from 2007 to 2019. Their results suggest that increases in heat extremes and drought have caused a 3.5 per cent decline in yields relative to the 1974 to 2004 baseline. “Three per cent or so might not sound like much, but this is a major impact [on] the global food market, which regionally can trigger a severe crisis,” says Kornhuber.

The researchers then calculated the economic losses, based on FAO data showing how much farmers would have been paid for their produce at the time. Finally, they used the same approach to project future losses in several different emissions scenarios, assuming that some adaptation takes place.

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In a high-emissions scenario, known as SSP3-7.0, global yields will fall by around 35 per cent by 2100, with annual losses rising to more than $161 billion. “The production losses caused by heat and drought are around 855 million tonnes a year,” says Hwong, who presented the results at a meeting of the European Geosciences Union in Vienna in May. “I think that is equivalent to what around 2 billion people consume over a year.”

This could be an underestimate of the full impact of climate change for a number of reasons: it’s just three crops, and it doesn’t include flood, storm or rain damage, or the possibility that shortages could lead to big price increases, as is already happening with some other crops such as coffee and cacao.

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at Columbia University in New York says the study’s reliance on the statistical relationships between yield losses and extreme heat and drought could result in it overestimating the impacts by 2100. “Statistical yield models are great for explaining what’s happening now, and in the near past [or] future, but they are inherently unreliable when pushed into vastly different environmental regimes, such as high-emission climate scenarios by the end of the century.” Computer models of how plants are affected by rising CO2 and temperatures are better for projecting what will happen by the end of the century, he says.

at the University of Queensland, Australia, makes the same point. “Although models are not perfect, they are better suited for this type of extrapolation.” However, her team recently released a , which hasn’t been peer-reviewed, showing that two widely used models for wheat make large errors and are especially poor at forecasting the combined effects of extreme heat and drought.

But Kornhuber has defended his team’s use of statistical methods. “The models are remarkable tools, but some of the validation papers have suggested that they might not be super responsive to extremes,” he says. “In our project, extremes were the main focus, so we decided to establish these relationships directly through statistics.”

Albert Einstein’s theory of special relativity can reshape chemical bonds within molecules, and researchers have just seen it happen for the first time.

The theory of special relativity describes how moving at speeds close to the speed of light would affect travellers’ experience of space and time. Because of this, it is usually associated with particle accelerators and spacefaring objects, but within some heavy atoms, electrons experience relativistic speeds too.

at Brown University in Rhode Island and his colleagues have now managed to take an unprecedented look at how this breaks the standard notion of chemical bonds within a charged molecule made from bismuth and carbon.

Within the molecule, a bismuth atom and a carbon atom were connected by three bonds, one of which the researchers expected to be of “sigma” type and two of “pi” type. The difference between these two types stems from electrons’ quantum character – each electron is “smeared” across some region of space, instead of being a tight ball, and whether these regions overlap head on or side by side determines the type of chemical bond they create between the atoms.

In their experiment, Wang and his colleagues mapped the distribution of electrons throughout the molecule, effectively getting a look at its bonds. But instead of seeing electrons distributed in shapes associated with sigma and pi bonds, the team noticed that two of the bonds resembled two different mixes of sigma and pi shapes. “Their characters are different from our normal understanding,” says Wang. “You can’t really call it the sigma and pi.”

His team turned to at Washington State University, whose calculations ultimately showed that this mixing was a consequence of electrons near the bismuth nucleus feeling such a strong electromagnetic interaction that they moved at relativistic speeds. He says this effect hadn’t previously been captured in an experiment.

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“The hardest thing about [studying] heavy elements is a lack of really good experimental data,” says Peterson. “To have such a beautiful experiment to be able to essentially compare very high-level theory to data is really a luxury.”

Wang says one important part of the new experiment is that he and his colleagues could make the molecule very cold before looking at its electrons. This dampened any jitters and excitations that would have made the final images imprecise.

“As you go down to the bottom of the periodic table, the usual quantum mechanics is no longer sufficient, you need to take into account the effects of relativity,” says at the University of Toulouse in France. He says that all elements in the same row of the periodic table as bismuth are affected by relativistic effects – for instance, gold would be the same colour as silver and mercury would not be liquid without them.

at the University of Helsinki in Finland says that for bismuth, the relativistic effect on its bonding with carbon could influence how organic bismuth compounds are used in chemical reactions. In fact, by researchers at the Max Planck Institute for Coal Research in Germany has already shown that relativistic effects help make this heavy metal a good catalyst, or accelerator, of chemical processes.

Wang says that the team now wants to repeat their experiment but swap bismuth for elements close to it in the periodic table to see when exactly special relativity makes the traditional chemical bond structure collapse.