NEWS & TECHNOLOGY Our brains trust made-up vision over what’s real SAYAKA WAKAYAMA ET AL Healthy pups bred from space sperm Alice Klein WE HAVE lift-off. Freeze-dried mouse sperm that spent nine months in space has successfully impregnated female mice and created healthy offspring. Despite growing discussion around space colonisation, there are still big questions about the viability of human reproduction off Earth. <strong>Scientist</strong>s say the high levels of radiation and low gravity could hinder conception or lead to abnormal development. Experiments have shown that fish and salamanders reproduce normally on space stations, but research in mammals is scarce. A handful of studies in the 1980s found that male rats produced less sperm in space, but sperm quality was not assessed. To address this, Teruhiko Wakayama at the University of Yamanashi in Japan and his colleagues sent freeze-dried sperm from 12 male mice to the International Space Station (ISS) in August 2013. The samples were kept in a -95°C freezer for nine months, before being flown back. Wakayama and his team then analysed the sperm’s DNA. They found that it was severed in several places – probably due to exposure to cosmic radiation. Radiation levels on the ISS are 100 times greater than on Earth because the station is not protected by the planet’s atmosphere and magnetic field. However, this damage did not seem to affect fertility or the health of offspring. Female mice implanted with the sperm via IVF had the same birth rate as those impregnated with freeze-dried “Mammalian eggs can repair damaged DNA. Essentially, the female fixes up the male’s mess” sperm that had not been exposed to space. The pups appeared healthy, and gene sequencing confirmed that they did not have any significant defects (PNAS, DOI: 10.1073/pnas.1701425114). The radiation damage in the DNA may have been repaired when the sperm cells were combined with the eggs, says Andrew Wyrobek at Lawrence Berkeley National Laboratory in California. Mammalian eggs are known to have a strong capacity for repairing damaged DNA, he says. “Essentially, the female fixes up the male’s mess.” To test the effects of space radiation on sperm-egg pairings, Wakayama’s team has now received approval to send frozen mouse embryos to the ISS. There, astronauts will thaw and culture them until they reach maturity. Then they will be returned to Earth and implanted in female mice to see if they produce healthy offspring. This experiment will also probe the effects of low gravity on early embryo viability. Previous studies have found that mouse and zebrafish embryos do not develop properly in simulated microgravity. So, even if embryos can successfully form in highradiation space environments, their growth may be hampered by the reduced gravity. However, we won’t know for sure without experiments in space, says Wakayama. Eventually, he would like to test whether live mice can mate normally on the ISS, because this would give the best insights into whether humans could safely conceive in space. “Nobody has tried it and we really want to know.” ■ SEEING shouldn’t always be believing. We all have blind spots in our vision, but we don’t notice them because our brains fill in the gaps with made-up information. Now subtle tests show that we trust this “fake vision” more than the real thing. If the brain works like this in other ways, it suggests that we should be less trusting of the evidence from our senses, says Christoph Teufel of Cardiff University, UK, who wasn’t –Astronauts before they were born– involved in the study. “Perception is not providing us with a true representation of the world,” he says. The blind spot is caused by a patch at the back of each eye where there are no light-sensitive cells. We normally don’t notice blind spots, because our two eyes can fill in for each other. When vision is obscured, the brain makes up what’s in the missing area by assuming that whatever is in the regions around the spot continues inwards. Now Benedikt Ehinger of the University of Osnabrück in Germany and his colleagues have asked 100 people to look at a picture of a circle of vertical stripes, which contained a small patch of horizontal stripes. The circle was positioned so that with one eye obscured, the patch of horizontal stripes fell within the other eye’s blind spot. As a result, the circle appeared to have no patch and the vertical stripes were continuous. Next to this was another circle of vertical stripes without a patch of horizontal stripes. People were asked to choose which circle seemed most likely to have continuous stripes. Ehinger’s team thought that people would choose the circle without a patch more often, as they could really see all the information in those. In fact, people chose the circle with a filled-in patch 65 per cent of the time. “We never expected this,” says Ehinger. “The brain trusts its own generated information more than what it sees outside in the world.” Clare Wilson ■ 14|<strong>New</strong><strong>Scientist</strong>|<strong>27</strong><strong>May</strong><strong>2017</strong>
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