Nature Podcast

This is a transcript of the 6th March edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to podcast@nature.com.

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Adam Rutherford: Coming up, are you thinking what I am thinking, we come a step closer to mind reading with a brain decoding device.

Jack Gallant: There are going to be issues that we are going to have to deal with here because it is going to be possible to do a fairly good reconstruction of people's thoughts.

Kerri Smith: And, the opening of a vault that will keep us fed should the apocalypse ever arrive.

Michael Hopkin: And, I have just helped to carry a box of mung bean seeds that has arrived all the way from India and will now have its new home here in the side of an arctic mountain.

Kerri Smith: Mike Hopkins' report from the seed bank in Svalbard coming up later in the show.Music

Adam Rutherford: This is the Nature Podcast. I am Adam Rutherford.

Kerri Smith: And, I am Kerri Smith. First this week, we are finding out about booms and busts in populations of midges living around an Icelandic lake. Unfortunately, for Charlotte Stoddart, the pod's travel budget would not stretch to Iceland. So, we packed her off on a train as far as Royal Holloway University on the outskirts of London.

Charlotte Stoddart: The appropriately named lake Myvatn, Midge Lake, in Iceland is home to Tanytarsus gracilentus, the green midge. Its population density fluctuates wildly by up to six orders of magnitude every four to seven years. These complex dynamics are the subject of the new study, which finds that human disturbances to the lake can cause the midge population to crash with knock on effects on the fish that feed on the midges and to the locals who like to eat the fish. One of the researchers, Vincent Jansen, is based at Royal Holloway University near London and I am on my way to see him. Hi Vincent nice to meet you. Nature 452, 84–87 (6 March 2008)

Vincent A. A. Jansen: Good morning Charlotte.

Charlotte Stoddart: So, first of all, how do these midges fit into the overall ecology of the lake that you studied?

Vincent A. A. Jansen: Well, these midges are very important for the ecology of the lake, because they make a large part of the biomass in the lake so much as about two thirds and to get some sort of an idea how much it is, you look out of the window, you see grasses and plants, think about two thirds of that is just a mass of insects, because they are so abundant and so dominant that is why they are very important in the ecology of that lake.

Charlotte Stoddart: As a mathematical biologist, Vincent, how did you get interested in midges?

Vincent A. A. Jansen: Well the way I got into this is through the first author of the paper Anthony Ives who worked with people in Iceland who have been monitoring these midge populations for a long, long time. What Tony did, he was thinking about what really these midges do and how you could explain that and in order to explain it, it always helps to have some sort of model and in this case, it is a mathematical model. Tony got stuck with a particular question on the modelling and that is why he called my help. It happened at the time when my wife was about nine months' pregnant and I had an e-mail come again, but the baby was late, so I found myself, sort of, sitting at home not having an awful lot to do and picked that e-mail open because the baby was late, I had a week to work on his story and that is why I produced positive results. So, that is partly how I got into it.

Charlotte Stoddart: And these midges I understand, they have quite an unusual, sort of, population dynamic?

Vincent A. A. Jansen: What is really interesting about these midges is that the numbers are very, very different over the years. So many years, you got just a few, other years they are very, very abundant, they are everywhere. If you see pictures, you cannot see the cloud or the sky almost for the midges, but what is unusual here is that the fluctuations in these numbers of midges are highly irregular they are not sort of just up and down. It is a bit here and a bit there, sometimes they are fairly constant then they have this enormous boom and bust cycles and that is what we tried to understand.

Charlotte Stoddart: So, what have you done to try and understand these really complex dynamics, this boom and bust that you described?

Vincent A. A. Jansen: Well, what we think it is here is that what is happening in these midges is what is called the alternative stable states. One stable state is being fairly constant in numbers, but the other stable state can fall into is these enormous boom and bust cycles. And what we think is that the midge population sort of flips between these two types of behaviours and to give you some sort of idea what that might look like think about an old grandfather clock with a big pendulum. That has also two stable states. If you wind it up, but if you do not touch the pendulum, it will stay perfectly still. If you give it a swing, it starts ticking and gives a regular swing, left-right, left-right. Now, imagine what happens if you put that grandfather clock at the back of a lorry and start driving, you would note a thing that sometimes the pendulum would hang fairly stationery. There is a bit of a wobble because of the knocks it gets from the lorry, but every now and then it might fall into resonance and start giving these regular cycles and what you would see is a fairly, sort of, irregular flip between a regular swing and a wobble and that is what we think is happening in the midge population in Myvatn.

Charlotte Stoddart: What do you think it is in the midge population that is causing this flip; changes between these different stable states?

Vincent A. A. Jansen: It is something like irregular knocks things like the weather, small things; small change in the environment that knocks us from one state into the other.

Charlotte Stoddart: Why should we care about these midges, why is it interesting and useful for us to know about the population dynamics?

Vincent A. A. Jansen: Well, first of all, this is a major question of Ecology trying to understand what is going on and I think what is really nice about this study is not so much of modelling, but the fact that it is 25 years of data and that is quite rare. It was a long data set. You can really start to look at that in detail to understand what is going on. So, it is one aspect that makes it a bit interesting in just finding out what is going on. But there is more than that. It has quite serious practical implications. What happened in Myvatn, there was a local fishery, people were fishing for Arctic char and that fish is a local delicacy and people liked an awful lot. For some reasons in the last few years, that fishery has completely collapsed and the fishes are gone and the reason we think it is because the amplitude, these swings in the midge population have become more pronounced and the fish population basically ran out of food, they eat the midges and that is what has gone to understanding. The midge population tells you an awful lot about all animals in the lake and the whole ecosystem.

Charlotte Stoddart: When I was reading the paper, you talk about on how the influx of algae for example and Tanytarsus can have a big effect in the midge population?

Vincent A. A. Jansen: Yes.

Charlotte Stoddart: I wonder if you could talk just a little bit more about that.

Vincent A. A. Jansen: That is really a very important part, because in this boom and bust cycles what happens is the midge population starts growing and growing in numbers to the point that they would have used all their food resources and once that happens the midge population collapses or there are a very few left, but also importantly they reduce the algae population, which they feed on. Now, what happens in that lake is there is a continuous trickle of algae and the Tanytarsus from all the parts of the lake and that could set off the next cycle. If you change that trickle of nutrients into those parts, if you reduce it for instance, your cycle has got more and more extreme and that is what we think that local fish population might have collapsed. There seems to be a link with Diatom mining in the lake when they are dredging part of the lake and that might have sort of interfered with that trickle of algae into other parts of the lake, which might have made the fluctuations in the cycles of midge more extreme and that is a potential cause or link for the disappearance of fish population.

Adam Rutherford: Vincent Jansen ending that report from Charlotte. Next up, in the most jet-setting episode of the Nature Podcast yet, we sent Geoff Brumfiel to the Large Hadron Collider, the mammoth particle smashing experiment being set up in Switzerland by the European Organization for Nuclear Research. The last pieces of this immense puzzle are falling into place, but are they ready for the off.

Geoff Brumfiel: Switzerland is generally a pretty serene place, but beneath its gently rolling pastures, an army of physicists is putting in overtime and stressing out. One hundred meters below the surface, these researchers are working frantically to finish the world's largest particle accelerator. It is called the Large Hadron Collider and at 27 kilometres in diameter it is arguably the largest scientific instrument ever assembled on planet Earth. Jim Virdee is head of the Compact Muon Solenoid or CMS, one of four giant detectors scattered around the ring of the Collider.

Jim Virdee: We are trying to address some of the most fundamental questions perhaps in science. What is the origin of mass? What is the dark matter made of? Do we live in more dimensions than four? Now these are issues which actually go back to the origins of our universe.

Geoff Brumfiel: The Collider slams protons together at 7 tera-volts, re-creating conditions just one-thousandth of a nanosecond after the big bang. Now, that is not the easiest thing in the world to do. To get the protons moving and keep them on course requires a huge system of superconducting magnets. Lynn Evans is the man responsible for getting those magnets and the rest of the accelerator running.

Lynn Evans: I have been working for 13 years on this machine. Normally, a project would be two to four years, but this is more like building a cathedral in building a particle accelerator in the old sense.

Geoff Brumfiel: Evans and his team are now working around the clock to get the Collider smashing protons. Their main problem at the moment is the magnets. They only function at about a degree above absolute zero and the frigid temperatures put stress on the Collider's vast vacuum and electrical systems.

Lynn Evans: As we cool down, then the risk of off-springing a leak or having a ground fall of one of the big electrical circuits is higher. We have had a couple of cases like that.

Geoff Brumfiel: Meanwhile, the four groups building the detectors that will study the collisions have their own problems to deal with. Each instrument is the size of a building and has thousands of components from all over the world. Now, everything has to be wired together. Jim Virdee again.

Jim Virdee: Within CMS there are about 30,000 cables and each one has an average length of about 100 to 150 meters. So, you can see that this is a vast enterprise and it has to be done very, very carefully, because we cannot actually send things from one place to a wrong place.

Geoff Brumfiel: Eventually the data comes here to the heart of CERN's computer network, where the team faced their last great challenge: handling data, lots of data. Francois Grey is a physicist in CERN's IT Department.

Francois Grey: We are expecting something like 15 petabytes, 15 million gigabytes of data that is about 3 million DVDs that is a stack of DVDs at the height of Mont Blanc.

Geoff Brumfiel: To share the data with thousands of collaborators around the world, CERN has developed a whole new type of internet. It is called a grid and it works by distributing both data and actual computing power to workstations across the globe. The grid is working well so far says Grey, but...

Francois Grey: We are testing it now with 20, 30 experts per experiment, what is going to happen when thousands of professors and their students start to, you know, submit jobs and ask it to do things and make mistakes as well.

Geoff Brumfiel: Despite formidable work to be done at very stage, CERN's physicists are optimistic that they can get their Collider up running soon. The schedule at the moment calls for beams of protons to begin circling around the machine in mid June. It might seem a tad ambitious given all that must be done, but the physicists on the project are going flat out. Lynn Evans again.

Lynn Evans: People are very motivated. I think now they see the end. They want to see the end of this project and to see some real physics coming out.

Geoff Brumfiel: If all goes to plan, data should be streaming out of CERN to labs around the world by the end of this year.

Kerri Smith: Geoff is with us in the pod this week. Hi Geoff.

Geoff Brumfiel: Hello, Kerri.

Kerri Smith: Now, it is the Annual American Physical Society Meeting in New Orleans this week and you have been working on a special Nature Podcast for the physicists out there.

Geoff Brumfiel: That's right. This is to accompany Nature physics milestone supplement about spin.

Kerri Smith: So, give us a brief idea what do you mean by spin?

Geoff Brumfiel: It is pretty simple really. I mean, all it really means is that fundamental particles spin in some classical sense like a top or a spinning wheel. It is a little more complicated because they are so small and they obey the laws of quantum mechanics, so this spin is quantized. That is all there is to it. I spoke to Frank Wilczek about it. He is a Nobel Laureate, who has done some pretty impressive work with the standard model of particle physics and quantum mechanics, and he explained why spin was important.

Frank Wilczek: It has become more and more central as physics has developed in the 20th century. We realized that together with mass and charge, spin is kind of the other fundamental label that we have to associate with the building blocks of nature. So, it is a really basic ingredient of our fundamental theories of nature and it has also become an extremely important tool for technology.

Adam Rutherford: Okay Geoff that was Frank Wilczek explaining why it is been as important, but what abut the practical applications of this phenomenon?

Geoff Brumfiel: Well, it is not immediately obvious it would have any practical applications, it certainly does not show up in nature very much outside of particle experiment, but it turns out that you can do quite a lot with it and the rest of the Spin Podcast will talk about that if you really want to know more. One of the people we lined up was Richard Ernst who is another Nobel Laureate, who won for the most widely used application of spin and that is Nuclear Magnetic Resonance or what they call in the medical circles, Magnetic Resonance Imaging. So, that is basically using spin to look at the body and all sorts of things really. It is really a fundamental tool across science these days.

Adam Rutherford: And we just heard your report from the LHC and CERN, when it finally cranks up, how is that experiment going to add to our understanding of spin?

Geoff Brumfiel: Well the LHC and the detectors there are going to be looking for something we have not seen before and that is a fundamental particle with zero spin. It is called the Higgs particle or the Higgs boson and it is believed to endow all other particles with mass. So, it would really be quite a find although actually in that case the spin is probably one of the less interesting aspects of the particle.

Adam Rutherford: Okay, thanks Geoff, the milestones in spin supplement is available at http://www.nature.com/milestones/milespin and the podcast is there as well. It is also available on the Nature RSS feed.Jingle

Kerri Smith: Now, it is time for The Podium. Here is Nature's news Editor, Alex Witze. Nature 451, 1030 (28 February 2008)

Alex Witze: Texas is a fun place to be a science reporter. I ought to know. For nine years I worked for the Dallas Morning News. It is the leading daily newspaper in the heart of the Bible belt. I used to write stories about everything, from Space Exploration to nanotechnology, but it was always the evolution stories that got to me. I would write up some innocent little piece about a new dinosaur find and I would get a flood of letters protesting that I had said the fossil was 90 million years old. Readers were polite most of the time, sometimes they would accuse me of being a Darwin, other times they tell me exactly where they thought I should go, after all this is the state where the Education agency fired its Science Director, all because she forwarded an e-mail about a talk dismantling Creationism. Now, there is even more incredible news coming from Texas. The State Higher Education Board is considering giving the Institute for Creation Research the ability to grant masters degrees in Science Education. Yes, you heard me. The Institute for Creation Research granting masters degrees in science education. Texas is the kind of place where this idea isn't automatically laughed off the table. Okay, it is not really clear how strongly the Education Board is considering it. For now, they have just asked the creationists to answer some more questions like why their curriculum is so different from every other science education program in this state. In April, the board will decide what to do. Now, scientists are some of the angriest about this proposal and rightfully so, it is a really bad idea, but I talked to a lot of scientists for my job and sometimes I think they do not talk enough to regular people. They do not understand why creationism has such a foothold in the US, but they do not bother trying to figure out why. In Texas, some students get really conflicted when they go to science class every day. They want to learn, but they also do not want to get their parents mad and sometimes they end up taking it out on their teachers. I have interviewed biology teachers before, whose students yell at them saying they think they are doing the work of the devil, and everyone ends up leaving the classroom mad. Academics tell me they cannot believe Creationism still has any supporters. I say, these academics have not been out of their labs. If you want regular Americans to understand why Science trumps Creationism you need to get out of your ivory tower and talk to people. They are ready to listen, but they need to hear from you.

Adam Rutherford: Nature's Alex Witze on the Podium. Coming up in just a moment, Kerri will be engaging in a spot of mind reading, but on the final leg of our European tour, Mike Hopkin wraps up and ventures out to the frozen island of Svalbard, halfway between the northern most tip of Norway and the North Pole.

Michael Hopkin: I am standing inside the Svalbard Global Seed Vault tunnelled into the side of a mountain on a remote Norwegian island just a few hundred kilometres from the North Pole. That eery sounding music you can hear is because I am at the opening ceremony of the seed vault, which aims to hold a backup copy of almost every crop seed that is being cultivated anywhere in the world. The tunnel I am standing in which reaches a hundred meters into the mountain has at the end of it, three vaults where seeds will be kept in cold storage at minus 18 degrees centigrade. 150 delegates from all over the world have come to help load up the first seed collection and I have just helped to carry a box of mung bean seeds that has arrived all the way from India and will now have its new home here in the side of an arctic mountain.

Cary Fowler: Well, we are pretty far away from the dangers of the world right here and sometimes people ask me, do you think there is anything that can go wrong. There is nothing that can go wrong that I can think of.

Michael Hopkin: That was Cary Fowler speaking at the opening ceremony as Executive Director of the Global Crop Diversity Trust the organization that will run the seed collection, he has been the driving force behind its construction earning him the nickname the 'Modern-day Noah'. The vault itself has been dubbed the 'doomsday vault', because it will hold backup copies of all the world seeds should they be lost from their native countries. Back in the warmth of the hotel, Fowler told me how the vault will help to safeguard the world's vital food crops.

Cary Fowler: It is important to have an insurance policy for normal seed banks around the world that are the chief direct suppliers of crop diversity to plant breeders and researchers and sometimes farmers.

Michael Hopkin: And you describe it as an insurance policy. Does that mean like many insurance policies people are hoping that they won't have to use it?

Cary Fowler: Oh, absolutely. Nobody wants to use their insurance policy. You do not expect to have an accident when you go out of the house in the morning and get in your car, but unfortunately we know that we are going to have such accidents and we know we are going to need this insurance policy. If we had built this vault ten years ago we would have used it at least ten times already and for some major disasters for the loss of the gene banks in Iraq and Afghanistan, but I must say that we do not have to have a major disaster in order for this vault to kick into use. We are losing crop diversity everyday. We loose it because of mismanagement and lack of funding and human accidents and equipment failures and all kinds of problems that are something short of apocalyptic, but in this very real sense doomsday is every day for at least some variety of agricultural crops.

Michael Hopkin: And, what is the idea of having that insurance policy based here in Svalbard?

Cary Fowler: This is absolutely the perfect location. Seeds require freezing conditions if you want to conserve them for a long time and here in Svalbard we get naturally frozen seed, if we put it where we are, which is inside of a mountain. So, we have done the calculations. We built a tunnel over 125 meters into a solid stone mountain, we know that is the coldest part of the mountain, we know it is going to be below freezing even 200 years from now, worst case climate change scenario. And there we do not have to depend on mechanical freezing, but we will have equipment to lower the temperature still further to minus 18. Somebody may say well 500 years from now will it be naturally frozen and I cannot answer that question, but I will say that 500 years from now it would be naturally insulated and a good place to keep them frozen.

Michael Hopkin: So, how many seeds actually went in there today and what is the ultimate aim, how many crops and seeds are you going to have represented there?

Cary Fowler: Today, there were over 100 million seeds that actually went through the door of the vault and that represent over 250 thousand unique varieties of agricultural crops. We think there are about one and a half million unique varieties of agricultural crops including a few that cannot be stored in these conditions in Svalbard. So, eventually we hope to get more or less one and a half million samples of our food crops up there and that would represent virtually all of the diversity of our seed-bearing agricultural crops.

Michael Hopkin: The idea of a secured bunker high in the arctic might sound like a rather James Bond style way to address the issue of world food security, but exactly how is a big freezer near the North Pole going to help those most in need, the farmers of African and Asia for example will have the most to lose from crop varieties dying out. I spoke to Jacques Diouf, Director-General of the United Nations, Food and Agriculture Organization.

Jacques Diouf: In developing countries, we do not have always the facilities, the resources to be able to keep these genetic resources despite their importance and their origin in those countries while here we have the low temperature which is natural, but also because we have the technology and we have the resources. The other element which is important is that because of climate change and particularly global warming, we run the risk of losing bio-diversity and this will happen essentially in tropical countries, in dry areas, where we also have some of the great potentials of bio-diversity; hence, the need in addition to the normal national, regional or international collections, that exists to duplicate somewhere these collections and be able to access such collection should the need arise.

Michael Hopkin: What sort of situations might arise where governments will call on the seed vault to provide copies of the backup seeds that it has?

Jacques Diouf: Well, a number of cases, drought, floods, hurricanes, earthquakes, or we may have more normal situations unfortunately of electricity cuts having an impact on capacity to maintain the low temperature of conservation and if you combine all those and unfortunately the increased frequency of this type of problem now in the world.

Michael Hopkin: But perhaps even so the nickname 'doomsday vault' is a little too downbeat. Speaking at the opening ceremony, European Commission President, Jose Manuel Barroso came up with an altogether more positive analogy.

Jose Manuel Barroso: People speak about this seed vault mentioned the 'Ark of Noah', but I think we can even go before to the 'Garden of Eden'. This is a frozen Garden of Eden.

Adam Rutherford: Jose Manual Barroso there, talking to Mike. Back in the comparative warmth of the studio for the final interview this week, Kerri.

Kerri Smith: I have been finding out about a new method of brain reading, decoding brain activity to figure out what someone else is seeing. The technique could one day be used for diagnosing diseases like stroke, monitoring how well therapies are working in the brain and even being able to read out the contents of your dreams. Jack Gallant and his team from the University of California at Berkeley started out trying to model the human visual system. Now, they have been able to use that model to predict which picture out of over a 100, a particular person is looking at, like the magician's, pick-a-card-any-card trick. He told me more about the report appearing on http://www.nature.com this week and some of its implications. Nature advance online publication 5 March 2008

Jack L. Gallant: This paper presents the results of an image identification experiment on humans in an MRI machine. So, we are measuring blood flow from these people while they are viewing natural images, the images themselves have been chosen from a large set of images you can sort of think of it as a deck of cards and they look at these images in the scanner and our job is to try to figure out which image they saw from their brain activity. So, to me the easiest way to think about this is in terms of the magician's card trick experiment. I take a deck of cards, I stand them out, I have you pick a card, you look at the card, put it back in the deck and I have to guess which card you saw. We did that exact same experiment, except we did with natural images instead of cards. So, we put a person in the scanner, we showed them a large number of images and then we looked at the brain activity and we had to guess which image they saw from the set of known images. So, the way the problem was solved was each image that they could have seen was passed through the model and that model predicted a certain pattern of brain activity across all of the voxels that we have recorded in the scanner. We then compared all of those predictions to the brain activity we actually observed and we simply picked the prediction that looked the best.

Kerri Smith: So, you managed to pick the right card out of the pack?

Jack L. Gallant: Yeah, and when the deck of cards or deck of photographs has about a 120 images, we can do better than 90% correct.

Kerri Smith: Vow! That is impressive. Let us talk, sort of, with the beginning of this story. You guys were in the business of making models of the visual system, is that right, what is your long term, sort of, aim there?

Jack L. Gallant: The long-term aim is basically to make a model of all of the individual visual areas. It turns out that your brain is about 30% visual, people are highly visual animals and the visual system consists of probably something between 50 and 70 different visual areas or little modules, sort of, computational modules, and what we would like to do is create a computational model for each one of those areas.

Kerri Smith: What step have you taken in this paper towards those goals?

Jack L. Gallant: I think there are two advances in this paper that make it noteworthy. First of all, we have an underlying model of the brain that we are using to process the data here. So, instead of trying to do a brain-reading experiment, where we simply measure brain activity, analyze the signals statistically and try to guess what, sort of, category the stimulus came from, we actually take the visual stimuli as they come in, we process them through a model of the brain and we use that model to try to guess what stimulus the person saw. The second difference between this paper and other previous attempts to brain reading is that we are using natural images. So, in our view, if you really want to do full brain reading, it has to work on arbitrary natural images that could be drawn from the pool of all the things you could ever see or experience in your life and using highly, you know, artificial simplified stimuli just is not going to cut it. So, this is the first attempt to really deal with natural images in the brain-reading context.

Kerri Smith: So, we are more likely to see a daffodil, when we are used to, sort of, a stylized image of a square or something like that, that a lot of people would use in these kinds of experiments?

Jack L. Gallant: Exactly!

Kerri Smith: So, this begs the question, what do you need to do before you can then recognize a completely novel, never before seen picture, just from some one's brain activity rather than selecting one of these 120 or so images?

Jack L. Gallant: Well, that is in principle a much, much harder problem. It requires essentially having a very good model of the brain, a very good measure of brain activity and a very good understanding of the statistical properties of natural images, and we do not really have any of those three things at this time. So, there is a lot more work to be done before this is going to be a very powerful and general technique. There is going to be a lot more work that is going to need to be done before you are going to really do this thing in real time.

Kerri Smith: Now, what could we use one of those for if we had indeed developed that machine?

Jack L. Gallant: There are a lot of potential medical applications for a device like this. For example, if you have a drug intervention or you are trying to assess the results of a stroke or you are trying to do diagnosis for say dementia, if you are trying to discover what happened when you implanted say stem cells into someone's brain and they re-grew new connections. All of those kinds of purposes you would want to understand how the functional job the brain was doing changed over time. And one way you can do that is to essentially do some sort of brain reading procedure, where you actually reconstruct what was going on in their brain. You can imagine using this for, you know, various kinds of dream analysis or biofeedback or psychotherapy.

Kerri Smith: Will it be a while? Then I do not need to worry yet about there being a way into my most secret dreams?

Jack L. Gallant: No, no I think it is going to be decades before that happens. Basically, you could imagine that in a timeframe of say 20 to 50 years, there are privacy issues that are going to have to be considered very seriously. Once neural imaging becomes much cheaper, smaller, and more portable and more reliable and once the models of the brain, the computational models become much better, then there are going to be issues, I think, that we are going to have to deal with here because it is going to be possible to do a fairly good reconstruction of people's thoughts.

Adam Rutherford: Jack Gallant of UC, Berkeley. That is all from us this week.

Kerri Smith: And we were spoiled for choice for our Sound of Science. The blog 'Null Hypothesis' has just hosted a festival of science songs called 'Geek Pop'. There were many highlights, but here is a snippet of the pick of the bunch, Dark Matter by science troubadour Johnny Berliner, I am Kerri Smith.

Adam Rutherford: And I am Adam Rutherford, thanks for listening.[Sound of Science]

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Adam Rutherford: If you're all still listening here's your chance to win an iPod Touch courtesy of the Nature podcast.

Kerri Smith: First you need to listen to the following three sounds of science taken from the podcast archives from autumn last year and then go to our web site that's http://www.nature.com/nature/podcast and follow the link at the very bottom of that page. Here they come.[Music plays with three different sounds]

Adam Rutherford: So identify those three sounds and follow the link from http://www.nature.com/nature/podcast. This competition closes on the 31st of March 2008. Good luck and thanks for listening.(Music)