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Interviewer: Kerri Smith
This week, the brain cells that map where you are also know what you’re listening to.
Interviewee: Dmitriy Aronov
A neuron that during spatial navigation might be active in the north-eastern corner of the room would instead be active at C sharp.
Interviewer: Noah Baker
And, how trade is draining the world’s ground water supplies.
Interviewee: Carole Dalin
In some parts of India it might be just one or two decades until it’s going to become impossible to use it.
Interviewer: Kerri Smith
Plus, a new compound that can harvest the sun’s energy and keep the cost down. This is the Nature Podcastfor March the 30th2017. I’m Kerri Smith.
Interviewer: Noah Baker
And I’m Noah Baker.
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Interviewer: Kerri Smith
If brain regions had catchphrases, the hippocampus’s would be, ‘location, location, location’. For decades, neuroscientists have known that the hippocampus is active when a rat navigates its way through a maze, for instance. And studies of the hippocampus in London taxi drivers show a boost in size that’s linked to their exhaustive knowledge of the city’s streets. But a new study suggests that thinking of the hippocampus as purely a spatial navigation hub is a bit one-dimensional, or , okay, two dimensional. Neuroscientist Dmitriy Aronov and his colleagues at Princeton University in New Jersey thought they’d take the rats in their lab to a whole new dimension and see how their hippocampus got on with sound. Here’s Dmitriy.
Interviewee: Dmitriy Aronov
We don’t always navigate through physical space. For example, a jazz musician navigates by transitioning between musical chords [jazz music]. The relevant feature of experience for a jazz musician at any given point in time isn’t spatial location, it’s the musical chord that the musician is playing at that moment in time [jazz music]. So we essentially trained our rats to play a very rudimentary musical instrument in which they used a joystick to change the frequency of sound in their environment [changing frequency sound]. So, it’s definitely not jazz but in essence it’s similar because a musician might learn a sequence of sounds and a musician might learn that a particular sound follows another sound and in our case rats learned that there’s a sweeping frequency of sounds where higher frequency follow lower frequencies. And there’s a reward at the end.
Interviewer: Kerri Smith
And what did you see when the rats were listening to this sliding scale of frequencies?
Interviewee: Dmitriy Aronov
What we saw is that the same neurons that classically are known to respond to the animal’s location were instead responding to particular frequencies of sound. So a neuron that during spatial navigation might be active in the north-eastern corner of the room would instead be active at C sharp and it would really be the same neuron that would get repurposed depending on which task the animal was performing.
Interviewer: Kerri Smith
It seems mad that the brain would use the same neuron for these two wildly different concepts.
Interviewee: Dmitriy Aronov
And that is in a way bewildering because we are taught to think about the brain as having very specialised parts: a part that’s responsible for sound; a part that’s responsible for spatial location. To think that there’s a brain area that repurposes itself for whatever task is relevant to the animal, I think is the main and fundamental finding for our work.
Interviewer: Kerri Smith
And I suppose that anything that varies on a scale – temperature or light – could be coded like this.
Interviewee: Dmitriy Aronov
Perhaps and I would take it even further. When we think we transition between different concepts. We know that one concept is related to another concept and we can do mental navigation where we transition between different abstract concepts in order to solve problems.
Interviewer: Kerri Smith
So, when people first observed maps in the hippocampus that had to do with space, perhaps they just called them maps because they happened to be looking at space and they’re actually much more general.
Interviewee: Dmitriy Aronov
When a rat is performing behaviour like that, the most salient, the most relevant feature of experience to the rat is his location. So these brain areas represented location perhaps because that was the relevant variable.
Interviewer: Kerri Smith
That could translate to concepts and abstract ideas couldn’t it, as well as it could sounds or physical location?
Interviewee: Dmitriy Aronov
I think so. It may be hard to test this idea in rats.
Interviewer: Kerri Smith
Well, you’ve already taught them to play an instrument. You could at least try and teach them to philosophise.
Interviewee: Dmitriy Aronov
It’s a big leap [laughs].
Interviewer: Kerri Smith
What will you do next? Is there any other dimension you’d like to test?
Interviewee: Dmitriy Aronov
Well, rather than going in the direction of testing other primitive types of dimensions, I think an interesting direction would be to test navigation through more abstract spaces, perhaps something that’s not as simple as frequency which is changing in a monotonic fashion but concepts that are linked to one another.
Interviewer: Kerri Smith
Do you think that if this study and other studies find a similar thing that we might end up reconceptualising how we think the brain actually works rather than thinking about it as lots of different modules that do different, very specific things. There might be these modules that do something very abstract.
Interviewee: Dmitriy Aronov
Well I think that’s what we’re shooting at. We’d like to go beyond the thinking that there are specialised brain areas, each of which performs a particular kind of function. If you think about your computer, there are components of your computer that are designed for arbitrary computation. Your hard drive can store images or it can store movies or it can store text. The individual components of your hard drive are not specialised for particular types of information. And there may be neural circuits that function in highly flexible ways as well – at least that’s what our data seems to suggest.
Interviewer: Kerri Smith
Yeah, it’s fascinating. It’s a good analogy as well because presumably people that are interested in building computers that look a little bit like brains should also take this into account – possibly already are – factoring in these networks that deal with more abstract information and concepts.
Interviewee: Dmitriy Aronov
I agree. I think that may be a way that we should start thinking about artificial networks as well.
[Jazz music]
Interviewer: Kerri Smith
That was Dmitriy Aronov who did this work at Princeton and has now started a lab at Columbia University. The music was called ‘Faster Does It’ by Kevin MacLeod.
Interviewer: Noah Baker
I’m surprised it wasn’t called ‘Ratmaninov’s Second’.
Interviewer: Kerri Smith
Very good.
Interviewer: Noah Baker
Rat king Cole? Rat Stevens?
Interviewer: Kerri Smith
Okay, you’re pushing your luck.
Interviewer: Noah Baker
Massive ‘R-attack’?
Interviewer: Kerri Smith
Alright, you can have that one.
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Interviewer: Kerri Smith
Coming up in the Research Highlights, giggling birds and ribosome drugs. First, a study corrals the far flung effects of trade on groundwater depletion.
Interviewer: Noah Baker
Digging up fossil fuels and burning them to power our lives is leading to dramatic climate change but fossil fuels aren’t the only unsustainable resource we’re pulling up from the depths of the earth. Ever heard of fossil water? Fossil water is ancient ground water: the gigantic underground water supply lurking beneath our feet. In recent years groundwater reservoirs including fossil water supplies have been increasingly tapped into for agriculture, so much so that they’re now under threat all over the world. Carole Dalin from University College London here in the UK has written a paper in this week’s Natureexploring how these water supplies are being exploited and how economics is driving the change. She joined me in the studio to explain more.
Interviewee: Carole Dalin
Groundwater is stored underground, so in some reservoirs that we call aquifers. They actually represent most of the available fresh water that we can use on earth. It’s 99% of fresh water.
Interviewer: Noah Baker
And this groundwater is really important for various aspects of the water cycle, but it’s also important for industry. And groundwater is used a lot in agriculture. Tell me a little bit about how that works.
Interviewee: Carole Dalin
We actually know that about 85% of overuse of groundwater is for irrigation. People were originally irrigating with water from a lake or from a river but more and more recently people have been digging wells and pumping the water to the surface.
Interviewer: Noah Baker
Now, you said 99% of the water – of fresh water supply – are in groundwater. It’s seems like there’s plenty to go around but there are over-exploitation problems that are coming from these sort of actions.
Interviewee: Carole Dalin
Yes so the other important thing is that what we call the residence time of the water in different reservoirs is very different. For groundwater it’s really long: it’s over a century on average. Whereas for surface water it’s a few years so some of this groundwater is what we call fossil groundwater so they are basically never going to be renewed in our lifetimes.
Interviewer: Noah Baker
What does this eventually come down to then? When are these limited groundwater supplies going to run out?
Interviewee: Carole Dalin
It is difficult to know exactly how much water is stored in these aquifers which is what you need to know on top of the rate of depletion to estimate when it will run out. Some research is on-going to answer that question but we know that also the main relevant factor is basically the depth, the length of the well that you have to dig to pump the water and then it becomes more and more costly to pump it. In some parts of India it might just be one or two decades until it becomes impossible to use it.
Interviewer: Noah Baker
Yeah, you mention those two factors there: the economic factors and then also the climatic factors. You’ve been looking specifically at those economic factors in this paper; so you’ve been looking at how trade influences that groundwater depletion. Tell me a little bit about what the key players are here?
Interviewee: Carole Dalin
Yeah, so, we found groundwater depletion clusters as we call them. So the countries are the United States, Mexico, China, Iran and Saudi Arabia. Those countries are old producers of food irrigated with non-renewable groundwater and they also import from partners who also use this type of water. They are both exposed in terms of their economy and their local supply but also in terms of their imports. Actually, for Saudi Arabia and Iran, they both depend on some of the most over-exploited aquifers in the world.
Interviewer: Noah Baker
And I suppose that makes sense. These countries have very low rain fall, they’re very hot. They might have to use their groundwater supplies to grow crops. But let’s take a different look and look at a country like the United States for example which is also one of these groundwater depletion clusters that you’ve mentioned. This is a country where certain parts of the country have a large amount of rainfall and others have less and yet they still are importing food from countries which are over-exploiting their groundwater supplies and they’re over exploiting their own in the food that they’re exporting. That doesn’t seem to make sense to some.
Interviewee: Carole Dalin
Yeah, so actually the reason why it doesn’t make sense when you know about the groundwater issue is that this issue is not reflected in the price of the food. So, in the case of the US imports, it imports for example citrus crops – so lemons, oranges – from Mexico and they are actually in some parts irrigated with over-exploited aquifers but that’s not put in the cost so we just keep importing them and consuming them.
Interviewer: Noah Baker
If we as a people, as a global community, want to try to prevent this over-exploitation of groundwater, of aquifers, what’s the solution? Is there an economic one? Is this what you’re trying to get at in your study?
Interviewee: Carole Dalin
Well, we are trying to provide the first step which is the quantification and I think there is still some work to do on that and if we want to eventually go to reflecting that in the price or including it more ‘integratively’ in the management of the resource, we need to measure it.
Interviewer: Noah Baker
We’ve talked about sustainable and unsustainable groundwater. Should the countries that are currently over-exploiting their aquifers, should they just not be growing food? Is there a way for sustainable agriculture to happen there if the way that they’re currently getting the irrigation they need to grow this food, if that’s unsustainable?
Interviewee: Carole Dalin
Farming is providing livelihoods to a lot of people – so to hundreds of millions of people – and so it’s difficult to just go and say, look what you’re doing is bad for the environment, you have to stop… because all these people won’t have their food supply and their jobs. Again, I think we have to start to try and first of all be aware of the issue and try to find solutions to reduce the issues of water so there are other solutions than just stopping growing crops. You can change the type of crops that you plant. There are regions where more native cultivars are better adapted. You can also save a lot of water by having more efficient irrigation systems with less leakage – these kinds of measures.
Interviewer: Noah Baker
That was Carole Dalin from University College London joining me in the studio here at Naturetowers. You can find out more about her work with groundwater and trade at nature.com/nature.
Interviewer: Kerri Smith
Just before we get to the Research Highlights, there’s still time to vote for us in the Listener’s Choice category of the British Podcast Awards. That’s britishpodcastawards.com/vote. Just search for Natureand fill in your name.
Interviewer: Noah Baker
Right, as promised, here are those highlights read by Shamini Bundell.
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Interviewer: Shamini Bundell
The sound of others laughing often makes humans giggle. Researchers know that in other mammals, joy can be infectious. A team wondered whether the Kea Parrot, famed for its playful nature might also get the giggles off its friends, so they recorded the warbling sound [Parrot noises] that the parrots make when they’re having fun [Parrot noises]. When the researchers played this back to wild keas it inspired the birds to start playing. So it seems laughter is even more contagious than previously thought. For the full paper, head to Current Biology.
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A newly discovered compound can interrupt the cell’s protein production line. It works by targeting the ribosome, the machine that translates genes into proteins. Crucially, it only halts the ribosome when it’s making one specific protein without preventing most other proteins from being made. The protein it acts on called PCSK9 manages cholesterol levels. Feeding the compound to rats reduced their cholesterol levels. Throwing a spanner in the ribosome like this could help develop new drugs. The full study is in PLOS Biology.
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Interviewer: Noah Baker
The sun’s light is an everlasting energy supply and there’s ways of turning it into electricity but with many of these methods you need rare and expensive metals. Wouldn’t it be great if you could just use one of the most abundant metals on the planet instead? Well, Kerri spoke to the researchers who have been doing just that.
Interviewer: Kerri Smith
Many chemical compounds can absorb light; they can take in photos from a light source and convert them into a train of electrons which is pretty helpful if you’re trying to build a solar cell or some other device that can harvest light and turn it into electricity. Or, the materials can take the photons in and emit them again a bit later, making the materials photo-luminescent. That’s handy if you want to make LED displays, for instance. Of course, there’s a sticking point. Here’s chemist Petter Persson of Lund University in Sweden.
Interviewee: Petter Persson
Many materials that use these light-harvesting complexes, they very often have used rare and expensive metals.
Interviewer: Kerri Smith
Petter is talking about elements like ruthenium, a rare earth metal. There really isn’t very much available – about 5,000 tons total. Naturally then, chemists would like to find some magical material that worked just as well but which they could make out of something much more ordinary.
Interviewee: Petter Persson
And it’s really been a driving force for this project from the start that we want to see if we can use this really earth abundant element. If we get there this will be very suitable for large scale energy applications.
Interviewer: Kerri Smith
Petter Persson, together with his Lund University colleague Kenneth Warnmark and their team, went to the other end of the abundant scale for a new piece of work reported inNature. They’ve used one of Earth’s most abundant elements. It forms 5% of the Earth’s crust. One billion tons of it is mined every year. Here with the answer to the quiz is Felix Castellano, a chemist at North Carolina State University, not part of the Swedish team.
Interviewee: Felix Castellano
Iron is the most abundant transition metal on the entire periodic table in terms of how much you’ll find in the Earth’s crust. Iron is just readily available so if you could make the transition to iron from these ruthenium and iridium types of transition metal complexes, you’d be really taking a good step in the right direction.
Interviewee: Kenneth Warnmark
And that is, I think, the main thing that we have actually managed.
Interviewer: Kerri Smith
This is Kenneth Warnmark speaking.
Interviewee: Kenneth Warnmark
We have been able to tune the iron to resemble the ruthenium.
Interviewer: Kerri Smith
The team took iron and joined onto it a kind of chemical scaffold that they’d carefully designed. The scaffold basically holds the iron in a configuration where exposure to light forces it to accept an electron which excites it. Once the electron is excited its photons start to move and it can transfer this charge to another material which can carry it on to its final use, say, in an electrical grid. But there was one more problem to solve here. Complexes like this need to hold on to their excited state for long enough to transfer charge to another material that can then make use of it. In the past, researchers couldn’t manage to keep iron-based compounds excited for long enough, but here they’ve measured the longest excited state lifetime ever seen for iron: 100 picoseconds. Okay, that’s only a hundred trillionths of a second but it’s long enough, says Kenneth Warnmark.
Interviewee: Kenneth Warnmark
For the eye of a human being, you can’t observe such a lifetime but in the world of molecules, 100 picoseconds, that we have here, it’s a lot of time.
Interviewer: Kerri Smith
There is clearly no shortage of iron to use for this purpose and the scaffold is made from common elements too, like nitrogen and carbon. But could this scaffold be bolted onto other metals? Will it work in other scenarios? That could be useful if other metals could hold on to an excited state for even longer, or have other useful properties. Felix Castellano again…
Interviewee: Felix Castellano
Interviewer: Kerri Smith
At the very least there’s likely to be a proliferation of new research exploring these new designs.
Interviewee: Felix Castellano
This paper is poised at least to challenge the community to seek out alternatives using these concepts.
Interviewer: Kerri Smith
Felix Castellano there, at North Carolina State University and the author of a News & Views article on the new paper. That’s at nature.com/nature along with the paper itself by Kenneth Warnmark, Petter Persson and their team.
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Interviewer: Kerri Smith
It’s the news now and reporter Dan Cressey joins me in the studio – welcome Dan.
Interviewee: Dan Cressey
Hello Kerri.
Interviewer: Kerri Smith
You’ve brought us an update on the animal tree of life which we’ll get to in just a bit but this week’s lead story is a selection of personal takes from researchers whose lives have been touched by Brexit. We should start with the Brexit latest for our international listeners. What’s happened this week?
Interviewee: Dan Cressey
Well, this week everyone is expecting that the government is going to trigger Article 50 on the 29thand that’s basically the formal process of leaving the EU. So, last year the UK voted and the majority of citizens who voted said that they wanted to leave the European Union and now the government is basically going to press the big red button that tells Europe we are leaving.
Interviewer: Kerri Smith
That does make it sound a little more certain but the situation for science and for researchers is still a little bit feeling your way in the dark, right?
Interviewee: Dan Cressey
Researchers know what they’re worried about. They’re worried about their funding because they currently get a lot of money from European Union sources and they’re worried about their staffing because a lot of scientists who work in the UK do so or are currently allowed to do so because they are European Union citizens and no one knows whether that’s still going to be the case in future.
Interviewer: Kerri Smith
Now, in the News section this week you profile a few scientists and researchers who’ve talked to you about their worries, hopes, dreams, fears for Brexit as the UK triggers Article 50. What are some of the takes that you collected – you and your colleagues I should say?
Interviewee: Dan Cressey
Yeah, this is a team effort from people in London and across the European Union, from our various different reporters and some of these people are taking a very positive approach. One is Simone Immler who is taking up a job at the University of East Anglia in Norwich. She is Swiss and she’s moving from Sweden so she is very much one of these European Citizens who is very mobile and she is still coming to the UK. She is taking a glass half-full approach and she says she’s generally optimistic and she doesn’t think that she’s going to have to leave again at the moment because she says that life would have to become very difficult for non-Brits in Britain and hopefully we’re quite far from that. There is some of that ‘we’re just going to get on with it – we’re scientists and we’re just going to do our science’.
Interviewer: Kerri Smith
So Simone’s finding room to be optimistic about her future and her husband’s future working as scientists in the UK. Not necessarily the case for the guy who’s running the EU funded Joint European Torus Fusion project.
Interviewee: Dan Cressey
That’s right. Ian Chapman who is the chief executive officer at the Culham Centre for Fusion Energy in the UK, he basically is spending about half of his time dealing with Brexit. He’s got a lot of European staff who are understandably worrying about what this means for their jobs. They get a lot of European funding because it is the EU funded Joint European Torus and Chapman says some of his top staff have accepted positions elsewhere, and that uncertainty of what’s going on is driving some of that.
Interviewer: Kerri Smith
So he’s been having some difficulty recruiting and one assumes that perhaps some destinations in Europe are somehow benefiting from scientists choosing to go to other countries over the UK right now with this atmosphere of uncertainty.
Interviewee: Dan Cressey
Yes we have another interview with Gerry Gilmore who works at the University of Cambridge and he is probably going to be put out of a job as a result of the UK leaving the EU. He co-ordinates Europe’s Optical Infrared Coordination Network for Astronomy and he thinks he’s going to have to hand control of that over to an Institution in a state which remains a member of the European Union.
Interviewer: Kerri Smith
Are there people elsewhere in Europe who are ready to, I don’t know, seize the opportunities that this might create?
Interviewee: Dan Cressey
I think that might be fair to say, yeah. I think there’s a feeling that if scientists are going to be less attracted to the UK, they’re not just going to sit around at home and not do anything, they’re going to look for jobs elsewhere and people are looking to capitalise on that. And we’ve seen this not just in science but elsewhere. Places are angling for UK businesses to move to a European headquarters and that’s true for scientists as well. These are highly mobile, highly sought after people. If they decide to up sticks and move, there are going to be people competing for their signatures.
Interviewer: Kerri Smith
Now there may be listeners who are frankly sick of hearing about politics, and much as we appreciate, Dan, you bringing this story to us, we’re going to go back now millions of years – hundreds of millions of years – to the controversial branches of the early animal tree of life. What is controversial about this?
Interviewee: Dan Cressey
What’s really controversial about this is what order these branches come in. So, obviously if we go back way past your grandparents and your great, great grandparents, all the way back to the ancestor that you share with all the other animals which is jellyfish and other fish and all sorts of weird things, the real question that a lot of people are trying to work out is which of those branches of the animal kingdom split off first. The row has really boiled down to sponges and comb jellies.
Interviewer: Kerri Smith
Can I ask first, before we get on to the sponges and the comb jellies, why evolutionary biologists are particularly interested in this question?
Interviewee: Dan Cressey
Understanding how things evolve is obviously really important and also, traditionally, the way that people have worked this out – what split off first – was they looked for the simplest creatures and they said that oh sponges, look they’re really simple, they must have split off first and then all of the other animals went on and became these wonderful complicated things like you and me and vaguely bilateral creatures. If it’s not the simplest things that evolve first, that must mean that either some of the things that you view as complications have evolved more than once, or that sponges maybe lost them.
Interviewer: Kerri Smith
So back to the two stars of this story – sponges and comb jellies. They’re the ones vying for position at the very bottom of this tree as I understand it.
Interviewee: Dan Cressey
Yeah, and for a long, long, long time, zoologists thought that sponges were clearly on the bottom because they’re squishy, simple things and lots of angry sponge biologists will probably write in now to tell us that they’re not simple and they’re really interesting and sponges are awesome, let’s put in that caveat. But in 2008, Naturepublished a paper that said comb jellies should be put at the bottom, not sponges, and team comb jelly came and they took the crown from the sponges and that basically has kicked off an on-going – war is probably too strong a term – but exchanges which say, ‘no it’s sponges’, ‘no it’s comb jellies’. And we’ve now got to the latest point in this.
Interviewer: Kerri Smith
What was the evidence for either one of them being the bottom of the tree? This paper that was controversial had to so with genetics.
Interviewee: Dan Cressey
Right, so what’s basically happened here was it used to be just like, ‘oh that looks simple’ – and I am horrifically oversimplifying this – and then we started to get genetic analyses. And these are horrifically complicated things to do and depending on how you do them depends on which animal drops out first at the bottom of the tree.
Interviewer: Kerri Smith
What’s the latest analysis added to this picture?
Interviewee: Dan Cressey
The latest paper bills itself as the largest and most internally consistent Metazoan scale super alignment to date. Basically, what that means is they crunched an incredible amount of genetic data compared to previous studies to try and work out which species did branch off first in the tree of life and this time they take it all the way back and they say… ready? Ready for the big reveal?
Interviewer: Kerri Smith
Not ready… I’m ready now.
Interviewee: Dan Cressey
It’s the sponges.
Interviewer: Kerri Smith
So it was sponges, then it was comb jellies. Now we’re back to sponges and again this is based on genetic evidence rather than the morphology of these things. So it’s looking at how similar genes and mutations in genes are basically in thousands of different species.
Interviewee: Dan Cressey
That’s right, but as one person we quote in the story says… they’ve got a large data set but almost certainly this is not the final word.
Interviewer: Kerri Smith
The most important question of all is, Dan, are you on team sponge or are you on team comb jelly?
Interviewee: Dan Cressey
As a Naturejournalist I am totally impartial in this.
Interviewer: Kerri Smith
And actually, whichever team you’re on, the picture of the sponge at the top of the story is very beautiful, as beautiful, almost as a comb jelly. You can read the story on nature.com/news and check out the Brexit vignette there as well. And while you’re there why not read this week’s impactful Feature on childhood cancers? That’s by Heidi Ledford.
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Interviewer: Noah Baker
This might come as a surprise to you because you’re obviously an insatiable consumer of podcasts but some people don’t even know what they are. We want to join other podcast producers in encouraging people to share podcasts that they think are awesome using the hashtag ‘trypod’ on social media – that’s ‘t-r-y-pod’. Thank you to those who have already recommended us.
Interviewer: Kerri Smith
That’s all for this week. Come and say hello on social media. We’re @naturepodcast and remember to vote for us: bristishpodcastawards.com/vote. Or you can always help us pout by leaving a review on iTunes.
Interviewer: Noah Baker
Next week we’re launching a brand new series of round-table shows all about the Grand Challenges: problems that science will need to work with other disciplines to solve. The first round table discussion is on global mental health and ties in with World Health Day which takes place on April the 7thand this year focuses on depression. Look out for the show wherever you get your podcasts on Monday the 3rdApril. Until then, I’m Noah Baker.
Interviewer: Kerri Smith
And I’m Kerri Smith.
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