JUANA SUMMERS, HOST:
It's time now for our science news roundup from Short Wave, NPR's science podcast. I'm joined by two of the show's reporters, Regina Barber and Rachel Carlson. Hey, y'all.
REGINA BARBER, BYLINE: Hi.
RACHEL CARLSON, BYLINE: Hi.
SUMMERS: So I know that you've brought us three science stories that caught your attention this week. Tell us what they are.
CARLSON: How running a marathon could change your brain.
BARBER: Fermenting food in space.
CARLSON: And the mystery of how bats in flight avoid colliding with each other.
SUMMERS: OK, I have to start off with this marathon one because I want to run my first marathon this year. So, Rachel, can you just tell me...
BARBER: Good luck.
SUMMERS: Thank you.
BARBER: (Laughter).
SUMMERS: Rachel, can you just tell me what does running do to our brains?
CARLSON: Yeah. OK, so especially if you're training for a marathon, I think we can both imagine that running one would take a lot of energy.
SUMMERS: Yes.
CARLSON: Neuroscientist Carlos Matute told me he's done 18 marathons, so he really knows it's exhausting. And he told me that he wondered, how do runners' bodies get the energy they need to make it to the finish line? His new research in the journal Nature Metabolism suggests their brains might be depleting a fatty substance called myelin.
SUMMERS: So it's sort of like your brain is eating itself...
CARLSON: (Laughter).
SUMMERS: ...When it's running low on energy?
CARLSON: Yeah, that's kind of how I was thinking about it. Myelin coats nerve cells and helps electrical signals travel, and it makes up about 40% of the brain.
BARBER: And after marathons, they saw that myelin decreased in the runners' brains, especially in the areas of the brain that are important for things like motor coordination, like how we move our bodies and sensory processing.
SUMMERS: So after a marathon, there's less myelin. Is that a bad thing?
CARLSON: Well, the changes were all temporary. The researchers followed up with the runners two months after the marathon and scanned their brains again, and they saw that the amount of myelin returned to normal.
BARBER: But there are some neurological diseases where myelin decreases and doesn't return to normal. Carlos thinks studying runners could help us better understand these disorders like multiple sclerosis.
CARLOS MATUTE: It may be useful to develop new lines of treatment for multiple sclerosis for slowing aging and perhaps neurogenerative diseases.
SUMMERS: Like neurogenerative diseases - OK, so for marathon runners or marathon runner hopefuls like me...
CARLSON: (Laughter).
SUMMERS: ...It sounds like we're all OK to keep on running.
CARLSON: Yeah, and the study has a few limitations. One of them is that they only looked at 10 runners' brains, so it was a very small sample size.
BARBER: Another neuroscientist in the field, Yannick Poitelon, told us the kind of scans the researchers took makes it hard to say, like, for sure that running caused the change in myelin, but he says that this study was really exciting. It's one of the first to show that human myelin could be used as an energy source, and he thinks it could inspire lots of new work in the field.
SUMMERS: All right, so next up, we've got fermenting food in space. I am always good for food stories. So what kind of food are we talking about here?
BARBER: Yeah, it was miso...
SUMMERS: Yum.
BARBER: ...OK? - the paste created from, like, fermented soybeans or grains. It's used a lot in Japanese cooking. And part of this study is in service of astronaut nutrition. Like, how do we make their diets more delicious, more nutritious, more diverse?
CARLSON: And the researchers were also wondering, how does this specific space environment - the space station - shape microbial life in unique ways? And understanding that's important for any kind of space travel.
SUMMERS: So how did this miso make its way into space?
BARBER: Well, Juana, it almost didn't. I spoke to Maggie Coblentz and Josh Evans, who published their study in the journal iScience this week, and Josh reminded me that, like, most fermented things have a really strong smell, and this fact almost stopped them from getting the experiment into space.
JOSH EVANS: The miso was ready to be put into the shuttle in Houston, and then we got this kind of - or Maggie got this, like, frantic call from someone from NASA being like, your payload is, like, kind of smelling weird.
(LAUGHTER)
BARBER: But fortunately, once NASA, like, got the explanation, they launched it anyway.
SUMMERS: So what did the researchers learn from this fermenting adventure?
CARLSON: Well, Maggie's big takeaway is that it worked.
MAGGIE COBLENTZ: Fermentation is possible in the International Space Station.
CARLSON: So if this worked, who knows what astronauts could get into next when fermenting stuff in space? Maybe sourdough, kimchi - I guess there's also stinky cheese, but I feel like if I were an astronaut, I'd be a little worried about that one. Personal choice, though (laughter).
SUMMERS: I mean, as a cook or an attempted cook, I'm sort of curious...
CARLSON: (Laughter).
SUMMERS: ...Did fermenting this miso in space make it taste any different than making it on Earth?
BARBER: Yeah, it did. When it came back to Earth, it tasted nuttier than the miso from the same batch, like, fermented on the ground.
SUMMERS: Interesting. Why do they think that happened?
CARLSON: So they don't know for sure. I could have been, like, radiation. It could be microgravity. It could be a combination of all of this, but the leading hypothesis is that it was mostly temperature swings inside the space station.
SUMMERS: All right, y'all, let's bring it home. We've got to end on bats. You say that scientists figured out how they avoid collisions?
CARLSON: Yeah, so this was a big mystery that perplexed researchers for a while. Like, basically, bats emerge from their caves, like, around dusk, all at once. There can be hundreds, thousands or even millions of bats in a group, all funneling out together. And for the most part, they don't crash into each other.
BARBER: And just a reminder, bats navigate using sound. It's called echolocation. They send out a vocalization, a call, and then they listen for its echo off objects in their path. But when a million bats are all flying out of a cave together, that's a lot of bat calls that could get mixed up. Here, let's take a listen.
(SOUNDBITE OF BATS CHIRPING)
SUMMERS: Oh, my gosh. Wow, that's incredible. So how did scientists sort of sort out all of these different calls?
CARLSON: Yeah, lead researcher Aya Goldshtein said one big innovation was tiny microphones.
AYA GOLDSHTEIN: We can put microphone on bats. We can track many individuals at the same time.
BARBER: Aya says scientists used to put microphones in front of the caves to measure the sounds of bats emerging, or they would have, like, a few bats in captivity, but none of this really got to an individual bat's perspective while in a densely packed group.
SUMMERS: Maybe we'll let them borrow an NPR producer to mic up their bats next time.
CARLSON: (Laughter).
BARBER: Yes. Yes.
CARLSON: Aya did this work while at Tel Aviv University in Israel. She and her team also used some new tracking technology using these little tags they put on bats to monitor their location. And when they combined acoustic data from these personal bat microphones, they figured out how a bat changed its call based on the density of bats around them, which they reported on in the proceedings of the National Academy of Sciences this week.
SUMMERS: Well, you've got to tell me, how do they change their calls?
BARBER: So they found that when the bats were, like, very densely packed, their calls were shorter, higher pitched, lower in volume and more frequent. And all of this essentially allows a bat to hear its own call echoed back instead of disappearing in, like, the ruckus of other bat sounds. Bat behavioral ecologist Rachel Page at the Smithsonian Tropical Research Institute in Panama, who wasn't involved in this work, said that this was a major advance in the field.
RACHEL PAGE: I think this is giving us insight that really is unparalleled, like, that you cannot get when you bring bats into a lab.
SUMMERS: Well, y'all, any lessons from this bat mystery that could help us humans?
BARBER: Yeah, Aya says that understanding how bats navigate could help engineers design flying robots that could swarm, which might be helpful in agriculture or environmental sensing.
SUMMERS: Ooh. That's Rachel Carlson and Regina Barber from NPR's science podcast Short Wave, which you can follow for new discoveries, everyday mysteries and the science behind the headlines. Thanks, as always.
CARLSON: Thank you.
BARBER: Thank you.
(SOUNDBITE OF HOT CHIP SONG, "COLOURS") Transcript provided by NPR, Copyright NPR.
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