Nature Podcast 13 July 2006

This is a transcript of the 13 July 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 mailto:podcast@nature.com

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Chris Smith: In this week's show, how eavesdropping on thoughts can be used to control computers:

Krishna Shenoy: We've implanted an electrode in the brain that allows a person to use their thoughts to control devices.

Chris Smith: The challenge faced by women pursuing a career in science:

Ben Barres: After you gave a talk, shortly after you changed your sex, I heard one of the faculty members say, Ben Barres gave a great talk today, his work is much better than his sister's.

Chris Smith: They were of course talking about the same person. And the world's smallest pair of tweezers:

Arno Rauschenbeutel: We have created a pair of optical tweezers that allows us to sort atoms one by one.

Chris Smith: Hello. I'm Chris Smith, welcome to this week's Nature Podcast. Now have a listen to this: ......... None the wiser? Well, that's actually the sound of the brain in action and researchers are now developing ways to eavesdrop on this activity to produce brain-computer interfaces. From Stanford University here's Krishna Shenoy. Nature 442, 195–198 (13 July 2006)

Krishna Shenoy: We have been trying to understand if we can record electrical signals from the brain to guide prostheses to help paralysed patients.

Chris Smith: So what exactly are you recording, and how?

Krishna Shenoy: We implant, neurosurgically, a small array of electrodes. Imagine a silicone chip like in your computer but with 100 tiny electrodes. This is implanted in the outer regions of the brain called the cerebral cortex and what it picks up upon are small electrical signals emanating from individual cells in the brain called neurons. These cells are responsive and relate to how you wish to move your arm and through mathematical algorithms we're able to interpret those neurosignals to predict which way one would wish to move their arm.

Chris Smith: So you're recording from the brain's motor areas principally?

Krishna Shenoy: Yes, we're recording actually from pre-motor cortex which is very close to motor cortex, which are the areas principally responsible for guiding your arm.

Chris Smith: And this is in an experimental animal?

Krishna Shenoy: Yes. In fact we use the Rhesus Macaque monkey model, and the reason for this is twofold. First and foremost we're very focused on trying to conduct science that can directly apply to humans. And because we wish to translate our work to humans we have to have an animal model that has a brain structure similar, called homologous to the human brain. The second reason is that we need to train our animals to perform rather complex eye movements and hand movements not unlike what a human would be able to do.

Chris Smith: So when you actually do this, just talk us through exactly what you train the monkey to do and what recordings you make, and how it essentially works.

Krishna Shenoy: Well, we train monkeys to look at a particular point of light on a screen directly in front of them and touch another point of light also directly in front of them, and then they play more or less a video game. So while they're looking and touching a screen right in front of them we turn on another point of light at some location and after some period of time they're asked to reach to that location. Now, the key is when the light comes on they know that they're going to have to reach there so they actually plan to move their arms there – something that we all do in everyday life but at a subconscious level. And while planning to reach to this point of light that's where we intercept these electrical signals from the brain and decode them which allow our computer algorithms to estimate where the monkey would like to move his arm.

Chris Smith: So with this sort of system in mind, and using a sort of keyboard analogy, if you want people to be able to, say, be able to type on a computer keyboard or a virtual keyboard just using their thoughts how many words would you anticipate they will get through in a minute with this?

Krishna Shenoy: We estimate roughly 15, that could be 13 to 15, and while it's a little bit complicated in terms of translating the exact speed and accuracy that we directly measure into this word equivalent that is absolutely how we think of it. Currently patients using existing systems might be able to type just a few words per minute and here we are able to advance that by roughly a factor of four.

Chris Smith: And Stephen Ryu who – you're the co-author on this paper – how do you see this actually being used clinically to, say, help people who have spinal injuries and so on?

Stephen Ryu: Well, Chris, the really exciting thing about this research technology is that we've always thought about what you could do if you could take somebody's brain signals and utilise them to control something, say a remote device – there's talk about controlling something, say, in Space so people wouldn't have to be exposed to dangers – but really more if you look at people who are normally functioning and, say someone who is a quadriparetic who suddenly loses the ability to use their arms and legs – such as someone like Christopher Reeves - you can imagine that their brain is still intact and therefore we could take advantage of those signals to help improve the quality of life. But in order to actually translate this to something which will be helpful to people we're going to have to take it to another level where we can show that they're both safe and that they're effective and can replace function that's already been previously lost.

Chris Smith: Stanford's Stephen Ryu, and before him, co-author Krishna Shenoy. But will it work in humans? Well, also in this edition of Nature Brown University's John Donoghue and his colleagues describe how they've implanted an electrode into the hand region of the motor area in the brain of a 25 year-old patient called Michael who's been previously paralysed by a spinal injury. The neural activity picked up by their electrode can then be decoded and used to control a computer. Nature 442, 164–171 (13 July 2006)

John Donoghue: The paper is about the technology that we've developed to help a paralysed person communicate with the outside world again, to be able to use their thoughts and for their brain activity to control devices, and mainly what we used was a computer.

Chris Smith: So is this literally recording from individual nerve fibres or is this whole populations of nerve cells that you're listening to?

John Donoghue: We're recording individual nerve cells, we're recording what's called the spiking activity, which is the language of the brain, and we record many of those at once – dozens to more than 100 – and we transform the pattern of spiking activity into a single control signal.

Chris Smith: So in order to record from the hand area of this person's brain you actually, presumably, have to implant an electrode?

John Donoghue: An electrode array is implanted. Yes.

Chris Smith: So what does that look like and how does it work?

John Donoghue: The array is about the size of a baby aspirin and it's implanted on the surface. It's 4 x 4 millimetres and it has 100 hair-like protrusions coming out of it. They go just into the surface of the brain, the cortex is about the thickness of an orange peel and the electrodes go about half that thickness into the brain to pick up the neurons that are just below the surface.

Chris Smith: And then how is that translated by your computer into a meaningful movement? And does the subject have to learn to control this?

John Donoghue: There's not actually a learning required to control it, the part that has to be learned is the relationship between a complex pattern of activity that's coming out of the brain and a desired motion of the cursor. So we have the patient imagine that they're tracking a cursor on a screen, and by the changes in brain activity that we observe while that patient is observing the cursor motion we build a map that says, here is the pattern of activity and here's the cursor position, and later on, here is another pattern of activity and here's another cursor position, and we try to map the two together. And of course another significant finding is we're able to do that. We do it over a period of about 15 minutes or so. So that's not really learning, it's establishing the mapping function. Once that mapping function is put together in the computer then the patient is able to just think about moving and the cursor will move pretty much in the motion that the hand would take if you were to imagine, say, moving left or right.

Chris Smith: How accurate are the movements that the person who has the implant fitted can make?

John Donoghue: So the motion of the cursor by thought is I would describe as wobbly and unstable, so right now, if your mouse performed like that it would be rather frustrating. And that's actually been part of our study, is to understand what happens as a person is exposed to that kind of signal? Do they get better and better at controlling it? And so far we haven't seen a major change in their control. And what that means is that at least we haven't found out how to exploit the brain's plasticity, so we need to change the computer to make the control signal better. And we're doing that and actually having some good success.

Chris Smith: Brown University's John Donoghue. But what are the outstanding questions raised by these studies? And how far are we from seeing the results translated to the clinic? Stephen Ryu again.

Stephen Ryu: The exciting thing about this research is that there's a lot of people that are involved because the early proof of a conscious system has shown that this is possible. There's clearly a lot of things that need to be done. There is research both in looking at the durability of the interfaces to the brain, such as the electrodes that are actually implanted because they would have to last a long time. And then the other thing is actually once you've extracted a signal from brains, how can you optimally take advantage of your signals to restore function? I think it's only a matter of time before we really start to see some true promise from these things.

Chris Smith: Let's hope he's right. And now to a very different human problem, the battle of the sexes and the challenge that science presents to women who want to pursue a career in it, especially after Harvard President Larry Summers suggested last year that females have less of an aptitude for science than their male counterparts. Well, that suggestion provoked Stanford University's Ben Barres to write to Nature explaining why it's just not true. Nature 442, 133–136 (13 July 2006)

Ben Barres: I decided to write this after hearing Larry Summers' comments about why women aren't advancing as scientists and he suggested, in his best guess, that women were innately less able than men in maths and intellectual abilities required to be a successful scientist.

Chris Smith: Well, perhaps at this point you should actually come clean, let's say, about your background and how you come to be interested in this subject?

Ben Barres: Well, I'm a trans-gendered person, I lived the first 40 years of my life as a woman and about ten years ago or so I decided to change sex, and I've had many experiences that lead me to feel pretty strongly about these issues and to be very aware from my own personal experiences of some of the forces that tend to hold talented women back.

Chris Smith: And have you noticed that life has changed enormously for you in the workplace?

Ben Barres: Well, certainly for the reason for my sex change had to do with inborn feelings of having been born the wrong gender. But I have certainly noticed that I have been treated differently since my sex change, particularly by people that weren't aware of my original gender.

Chris Smith: You give some quote that people anecdotally have said that your sister's work isn't half as good as yours?

Ben Barres: Yes, I just heard that recently from a friend when I asked them to read my commentary, they said, by the way, after you gave a talk at MIT shortly after you changed your sex I heard one of the faculty members say, Ben Barres gave a great talk today, his work is much better than his sister's.

Chris Smith: I mean, joking aside, what do you think is the solution to the present predicament that women find themselves in?

Ben Barres: The most important thing is that we need to have higher expectations. For women we need to all understand that they are cognitively as capable as men of being scientists, and we need to treat them as such from the time that they are born, onwards. I also think that women do bear the brunt of bearing the babies and childcare and the fact is it's not fair to expect women to advance at the same rate as men during their childcare years. There's nothing wrong – and I think we should do this more – to recognise talented women even if they're producing science. If they don't have a lab of 20 people that doesn't mean their science isnt' just as important as the man who has a lab of 20 people.

Chris Smith: And just to finish off, Ben, as a neurobiologist could you resist doing some tests on yourself from a cognitive point of view, when you actually changed from a woman to a man?

Ben Barres: People have been trying to sort out this issue of how much is nature versus nurture and so there are certain trans-gendered people have been an interesting test group to ask this question in do the cognitive abilities of women and men change when they change their hormonal status. And certainly in my case, I'm told that my verbal abilities had decreased. Now, I should make clear that these are very specific verbal abilities, but you should know that any cognitive differences between men and women are still quite controversial even whether they exist at all is very controversial, and so one of the things I think maybe the thing that annoyed me the most about Larry Summers' comments and why I thought they were so very unscholarly is he did not acknowledge, number one it's not clear there actually are cognitive differences, number two even if there are cognitive differences it's not clear that they're innate. And lastly even if there are differences are those differences relevant to the ability of women to be scientists? And I would say in every case the answer is, no.

Chris Smith: Stanford's Ben Barres. Nature's Podcast, bringing the world of nature to life.And now with news of avian flu, research and religion, and how oil rigs are helping biologists to take fantastic photos, here's Nature's Jo Marchant talking with Anna Lacey.

Jo Marchant: The first story that we've got is about an outbreak of bird flu in a family in Indonesia. I don't know if listeners will remember, we covered this in May. This was the first human cluster of bird flu, where it's thought that the virus had actually transmitted from person to person. The WHO released a statement shortly after this cluster – eight family members were affected, of whom seven died – saying that the viruses from each person had been sequenced and that there was no evidence of significant mutations. Beyond that they haven't made any of the information about the genetic sequence public and they say that the data belongs to Indonesia. But we've actually obtained some of the information so we've been able to have a look at what those mutations were. Nature 442, 114–115 (13 July 2006)

Anna Lacey: And what exactly does this data show?

Jo Marchant: Well, it shows that the WHO – you could say that they were correct when they said that there's no evidence of significant mutations, but the interesting things are firstly one of the mutations seems to confer resistance to an antiviral drug called Amantadene which is something that the WHO didn't mention in its statement, and the other thing is just the number of mutations. When you look at the relatives who caught it in first generation spread, if you like, there's between one and four mutations in each of those viruses. When you look at where the viruses have spread second generation there are 21 mutations across seven of the eight flu genes. Now, most of those are what geneticists call silent mutations, they're not actually affecting the amino acids used by the virus so there's no reason to think that there would be significant functional differences there, but just the fact that it's mutating that fast is quite interesting.

Anna Lacey: But you're giving figures there of about four mutations, 21 mutations, considering that influenza is actually an RNA virus and RNA is known to mutate quite rapidly anyway are these numbers actually that great?

Jo Marchant: Well, we do know that the virus when it's spreading between birds does also mutate quite fast. So that's true. I mean, we don't really understand very much about how fast it mutates in birds and we understand nothing about what it does in humans. So although we don't want to be too sensationalistic about this a lot of the virologists that we spoke to say that they'd love to be able to comment on the significance but they can't because that data is not being made available.

Anna Lacey: So why isn't this information being shared and what are the WHO actually going to do about this?

Jo Marchant: Well, the main reason it's not being shared is because... I mean, the WHO is made up of its member states so it has to do what they say, really, it doesn't have the authority to tell them what to do, and because these were cases in Indonesia that data is seen as belonging to Indonesia and Indonesia has not so far chosen to share that data.

Anna Lacey: Well, while we're on the subject of sharing, there's a new book out this month that's trying to create a more caring, sharing environment between the faith versus science debate. Nature 442, 114–115 (13 July 2006)

Jo Marchant: Yes, that's right. This is a book from Francis Collins who is the Director of the National Institute for Human Genome Research in the US, and he's got a book out this month called The Language of God, A Scientist presents Evidence of Belief. His basic argument is that you don't need to choose one or the other, there is a way to rationally combine the two.

Anna Lacey: But who is this book aimed at? Is it aimed at scientists, trying to get them to accept religion, or vice versa?

Jo Marchant: I think it's both, really. He says that the reason that he wrote this book is because the popular debate on faith and science seems to have become very dominated by extreme voices, it always tends to be those making the most extreme statements that get heard the loudest. So what he wanted to do is just say that there is a middle ground, you can believe in both.

Anna Lacey: But aren't there many scientists already who already believe in both? Is there any need for this book?

Jo Marchant: I think there are a lot of scientists who already believe in both, but I think there's a feeling that scientists can't really talk about it and won't really be taken as seriously if they do talk about it. So I think Collins is trying to encourage more debate amongst scientists about faith.

Anna Lacey: But irrespective of people's personal beliefs should scientists really be including the religious side of how they feel in the public presentation of their work?

Jo Marchant: Well, Collins obviously thinks that the answer to that is, yes. But there are others who are a little bit concerned about it. Some make the argument that science is a little bit on the defensive at the moment, not everywhere but in places like the United States where you've got this argument over embryonic stem-cell research and the argument over evolution versus intelligent design. So I think some people feel that really perhaps science needs less talk about faith and more about reason. But then other people have really welcomed the book and said that it's very helpful when a scientist of that prominence speaks out to say that the two things can be compatible rather than fighting.

Anna Lacey: Finally, this week, looking on the slightly lighter side of science, there's been a competition that's taken some snapshots of some of the wonders of nature. Nature 442, 116–117 (13 July 2006)

Jo Marchant: Yes, that's right. This is a competition for deep-sea images, it's being showcased at the International Deep Sea Biology Symposium in Southampton this week and they're just some lovely images, so we couldn't resist doing a picture special this week. Some of them are taken in the deep, some of them are creatures that have been collected and brought up to the surface and photographed there.

Anna Lacey: And so, Jo, tell us, what do some of these winning images look like?

Jo Marchant: They're weird and wonderful really. There's one that I love which is of a lantern fish, it's a real close up of its face and it looks absolutely mean, it's got these glowing eyes and shiny, wrinkled skin and it's got hundreds and hundreds of little, tiny teeth, and it has a huge frown, so it looks really alien. There's another one of the dumbo octopus which some people might have heard of, it's this vivid orange creature with a cute little smile as it looks like in this picture, and flapping ears just behind its eyes so it looks like a strange combination between a flying elephant and an octopus, I guess.

Anna Lacey: And how did people take these photos?

Jo Marchant: There's a variety of ways in which they've been photographed. Some are just frame grabs from remotely operated video cameras that have been sent down to the bottom of the sea, some have been taken, as I said, once the specimens have been brought up on to a ship, some are cameras attached to submarines that have been sent down. So there's all kinds of different ways in which they've been taken.

Anna Lacey: Well, they sound absolutely amazing, how can people have a look at them?

Jo Marchant: Well, we've got a picture special in the printed edition of Nature this week but we're also going to be showing them as a click-through gallery online, so if you go to http://www.nature.com/news you should be able to see them. There are some really nice stories behind them.

Chris Smith: Nature's Jo Marchant. This is Nature's Podcast from the 6th July edition of Nature with me Chris Smith. If you'd like to drop me a line about this or one of the previous editions of our programme then please email mailto:podcast@nature.com, and if you are online and you'd like to find out a bit more about any of the items we're discussing this week they're all available on our website at http://www.nature.com/nature. Coming up shortly how the atmosphere keeps itself clean and atomic tweezers. But first we're joining Jean-Bernard Caron from the Royal Ontario Museum in Canada to meet one of the earliest ancestors of modern molluscs. Nature 442, 159–163 (13 July 2006)

Jean-Bernard Caron: We discovered a soft-bodied mollusc from the Burgess Shale. The Burgess Shale is one of the world's most famous fossil deposits. It is a world heritage site in British Columbia in Canada. It is famous for its preservation and the preservation is exceptional, so that you can study animals in great detail.

Chris Smith: So what's important about the mollusc you found?

Jean-Bernard Caron: The importance of this discovery lies in the fact that this animal doesn't have any shell. What we know about early molluscs so far was only based on shelly remains, it's only because of the exceptional preservation in the Burgess Shale that for the first time we are able to tell that, yes, we have ancestors of molluscs that were shell-less.

Chris Smith: How do you know these guys came before the shelled version?

Jean-Bernard Caron: Well, we think that molluscs originally don't have any shell. The reason is that an organism found in Russia, called Kimberella, doesn't have any shell and this organism is found at about 555 million years ago. It was a creeping animal, possibly feeding on a cyanobacterial mat and possibly had a radular structure capable of eating this bacteria. The Burgess Shale is more recent, it's only 500 million years old, but it's just after the famous Cambrian explosion which represents the origin of animals. So it is significant, this discovery in the Cambrian because it tells us that there's a group of organisms from prior to the Cambrian explosion that connected to the Burgess Shale.

Chris Smith: So this is essentially where everything else was spawned from that's a mollusc today?

Jean-Bernard Caron: We think that early molluscs originated from a group that were shell-less, were ovoid, were flat and were eating cyanobacteria, and yes, Ondontogriphus is certainly one of these early offshoots of the mollusc.

Chris Smith: Can you just describe it for us? What it would have looked like, how big it was, that kind of thing?

Jean-Bernard Caron: This organism is flat, like the sole of a shoe, and it's a relatively large organism in the Burgess Shale, in fact it's one of the largest organisms we have. It can reach up to 15 centimetres. We also found juveniles up from half a centimetre, and this organism with its lack of striking morphological features was probably evolved to live a cryptic lifestyle.

Chris Smith: Jean-Bernard Caron on the trail of some of the earliest molluscs. And now what can only be called blue-skies research because Franz Rohrer from Germany's University of Jülich has been looking at the origins of atmospheric hydroxyl, OH, radicals which, because of their reactivity, play a key role in neutralising airborne pollutants like hydrocarbons and oxides of nitrogen. Nature 442, 184–187 (13 July 2006)

Franz Rohrer: The atmosphere needs some cleaning mechanism which removes all these pollutants and this is done by a very reactive species which we call radicals, and the most pronounced of these radicals are the OH radicals. They are introduced into the atmosphere by solar sunlight and then they react with all the pollutants and these are degraded in this process. And what we have seen is that the level of these OH radicals is very correlated to solar sunlight, and this is very astonishing to us.

Chris Smith: Would you not expect that because isn't the origin of these OH or hydroxyl radicals the interaction of sunlight with ozone?

Franz Rohrer: Yes, but you have to know that such a species like OH radicals has to be in balance with its production and destruction processes. Production is triggered by solar radiation but the destruction of OH, which is very fast, is done by pollutants, and so you should see the imprint of the production and the destruction processes. And all we find is the production process.

Chris Smith: So where has the destruction gone?

Franz Rohrer: There must be a coupling of processes because during the destruction of pollutants ozone is generated and the solar irradiation of ozone generates OH. So we have something like a recycling or a coupling of processes. And this coupling is not fully understood but it seems to stabilise the OH concentration.

Chris Smith: So what did people think was the case before this, then? Where did they think the OH was coming from and going to?

Franz Rohrer: The single processes, production and destruction processes, are known. But the full interaction of these processes, there must be something hidden in the system which is not fully understood because if you see we have these large mathematical models which calculate OH and if we compare these calculated OH levels with the measured OH levels they do fit less than solar radiation effects.

Chris Smith: So what is it going to take to find that missing link?

Franz Rohrer: The OH radicals generate their chemical environment because they degrade the pollutants and they generate ozone so they are also responsible for the generation of their production process. So we have to ask, how is it possible that OH shapes its chemical environment in such a way, and the difficulty is that OH itself has a lifetime of one second, and most of the pollutants have a lifetime of several weeks or months. So OH radicals are very locally and the pollutants are regionally or even continentally controlled. And so somehow the whole chemical system let's say of the northern hemisphere has to shape its chemical environment so that the OH radical is stabilised in its relation to solar radiation.

Chris Smith: Franz Rohrer, and the next step is to try to close that loop by uncovering the other chemical players and how they relate to ozone, sunlight, and hydroxyl radicals. Now, finally this week the world's smallest tweezers, capable quite literally of moving atoms around one by one. Arno Rauschenbeutel and his colleagues from the University of Bonn use two intersecting laser beams. Pointing the beam at a clutch of cooled caesium atoms causes the atoms to sit on the wave tips about half a micron apart, then by adjusting the phase of the laser light the atoms can be moved along like a conveyor belt. Nature 442, 151 (13 July 2006)

Arno Rauschenbeutel: We trap and observe single atoms which are trapped using laser light and what we have done now is to rearrange and manipulate these atoms so as to prepare regular strings of trapped neutral atoms.

Chris Smith: The caesium atoms?

Arno Rauschenbeutel: This is caesium atoms, exactly.

Chris Smith: So would this work for any kind of atoms as long as they're neutral?

Arno Rauschenbeutel: Basically yes, but the thing is that you have first to cool them down to a very low temperature in order to trap them using laser beams, and so this cooling mechanism works best with certain atoms, like caesium atoms and rubidium atoms.

Chris Smith: And how do you actually move them around and how far can you move them?

Arno Rauschenbeutel: Well, it's using laser beams as optical tweezers, so maybe you know that from biology where you can even manipulate cells using laser light and so what you need is a focused laser beam and you can move the atoms them by moving either this focus, or what we do is that we have two counter-propagating laser beams. So these laser beams not only have a focus but actually in this focus they have a standing wave structure, so that is like nodes and anti-nodes of light intensity and the atoms are trapped inside these antinodes, and so what we can do then is to move, like a conveyor belt, this trough of light, and move the atoms along the laser beam for a couple of millimetres.

Chris Smith: So you can move them along the X axis with a laser pointing, say, horizontally, and then with another laser pointing upwards you can move them upstairs, if you like?

Arno Rauschenbeutel: That's it. Actually if you trap the atoms in one laser beam in such a standing wave you cannot really influence the distance between the atoms, so the atoms are trapped in the individual potential wells but they will stay there. Now, if we want to control these wells in which the atoms sit we need an additional laser beam and an additional optical tweezer, if you like, and we can then extract the atoms out of this first laser trap and move them with respect to the other atoms which remain trapped, and so rearrange them by putting this extracted atom back into the laser beams.

Chris Smith: How do you know that the atoms are doing this?

Arno Rauschenbeutel: We can observe them, actually, by illuminating them with neo-resonant light, which is not the same light that we use for trapping them. We can just observe them using an optical microscope. So we take photos of the atoms and so we even recorded a movie of this process of rearranging the atoms, where you see the different steps of extraction and reinsertion of the atoms.

Chris Smith: And what sort of applications might there be for something like this? Because I remember when IBM famously wrote the letters IBM in atoms, I think they were xenon atoms, weren't they, using a tunnelling electro microscope. And they said, this is going to revolutionise the power of computing. Is this going to do the same?

Arno Rauschenbeutel: Actually it is of course, first of all, fundamental research, but we do this with the idea of using the atoms for processing quantum information. So we have shown that you can use such atoms which are trapped in a dipole trap as a memory for quantum information. And the idea is then to use some gate operation to process this quantum information, and actually then the answer is, yes, if you manage to process quantum information that can yield very much faster calculations concerning certain problems.

Chris Smith: Bonn University's Arno Rauschenbeutel. Well, that's it for this week, thanks very much for listening. Next time I shall be getting to the bottom of where the sea floor comes from. But for more news in the meantime do check out Nature's news blog, that's available from http://www.nature.com/blogs, and in fact this podcast is listed there and you can comment on it if you want to.Also, in this week's edition of The Naked Scientist podcast we're exploring the origins of allergies and how the methods evolved by parasites to evade the host's immune response might hold the key to allergy treatments of the future. That's The Naked Scientist podcast which is freely available from http://www.thenakedscientist.com. Additional production this week was by Derek Thorne and Anna Lacey, and I'm Chris Smith. Until next week, goodbye.

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