Decoding our inner voice, and hunting for life on Mars

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0:32scientists. Hello, welcome to the Naked Scientist podcast, the programme that brings you the biggest breakthroughs and talks to the major movers and shakers in the worlds of science, technology and medicine. I'm Chris Smith. Coming up, how scientists have now successfully decoded the voices in our heads. Also, direct evidence that ultra-processed foods make it harder to lose weight. And we hear from the PhD student who's aiding the search for life on Mars.

1:10Scientists at Stanford say they've decoded the brain signals behind our inner voice, the thoughts we hear in our heads, and with around 74 % accuracy. They implanted small electrodes into the region of the brain that we use to produce speech movements and then trained a computer to recognise the patterns of nerve activity that correspond to saying different words. The breakthrough could help people who can't communicate to speak again by turning their thoughts into speech. Erin Kunz at Stanford University led the study. Working with our participants in the previous studies in which participants attempt to speak but they have limited ability to do so due to, for example, ALS or stroke, we wanted to investigate a way that might be more comfortable or easier.

1:57So perhaps by imagining speaking instead of actually trying to speak. So bypassing the need for physical effort. The second motivation was that now as these systems are achieving impressive accuracies at decoding pretty much open-ended speech, we wanted to explore the possibility of these systems decoding something, words that the user may have not intended to be said aloud. So is this almost like when we talk to ourselves, it's that inner voice you're seeking to pick up and decode and turn into an output? Sort of. So we first were explicitly asking our participants to imagine aspects of them saying those words.

2:37So actually imagining the movement of their mouth or, for example, imagining the sound of their voice when they try to say the words. And how were you recording the activity? Because this is picking up on brain activity. isn't it? Yes so we're recording from the motor cortex so this is the part of the brain that controls basically our voluntary movement so when you want to move your hand or when you want to speak and specifically we're in the speech motor cortex so focusing in on those areas that control your mouth and your tongue and we're doing this with devices called microelectrode arrays they're about 3.4 millimeter square so smaller than a pea and these are placed on the cortex during a surgery and these have 64 electrodes on them, things that record the electrical signals of individual neurons firing in the brain.

3:24We can record those signals in real time for this study. There must be a long training phase then. So presumably you instruct your participant, think about this word or this sound and you must work your way almost like through a dictionary of different signature sounds or speech outputs so that you can work out what the different neurological patterns are that would correspond to each of those? Yeah, that's correct. So we cue participants with sentences on a screen. So for example, the sentence, I feel good. So the participant will see that sentence, and then they'll imagine saying that sentence.

4:00And then we do several of these sentences. So in the study, depending on the participant, they imagined between 80 and 500 of these sentences in order to train the models to decode the patterns of their speech that were associated with individual phonemes, individual speech units, basically. In the English language, we have 39 phonemes, and those are what make up the words. And so then the decoder can take that sequence of phonemes and identify what the most likely words were from them. And then what do you do? Flip it round. So you say, well, now it's learned what the brain does when we tell it to imagine saying X.

4:36Now we flip it round. We look at what it's saying it thinks the person said and ask them, is that what you really wanted to say? Yes, that's correct. So once the decoders are trained to identify those patterns, then the participants can imagine saying what they want and the decoder can decode that. And how accurate is it when you then start just looking at the activity that's coming out and then asking the person, is that what you were thinking of? How right is it? So it varied across participants, but in the best case scenario, we were able to get an 86 % accuracy when decoding from 50 words and a 74 % accuracy when decoding from a large vocabulary of 125 ,000 words, which would essentially be being able to say anything you want.

5:20Well, when one thinks about how many mistakes we make with fat thumbs trying to type text messages, that's pretty good. Yeah, it's pretty good. And also for reference, systems like Siri or Alexa typically get around a 95 % accuracy. So that's generally thought of being the sort of transition point between usable and not usable. Can it continue to learn though? Because obviously everyone's a bit different and it must be possible to pick up on foibles of how people think or tune it slightly more with time. So can it continue to learn? So will performance potentially continue to rise in these people or is it topping out at that roughly 75-80 % accuracy?

6:00Yes, absolutely. So this was an initial proof of concept. So we have pretty limited amounts of training data. And since this study was completed, we've continued to collect some training data. So we're still exploring the possibility of achieving higher accuracies with this type of device. And crucially, in the people with disabilities whom this could be applied to, where existing systems are quite fatiguing to use, trying to blink or look at things or breathe to move cursors around, is this a lot less cognitively taxing for these people so they find that communication is much more effortless?

6:37I think some participants report that it is less effortful. Some participants don't mind as much when they're attempting to speak. So I think it's just offering another option, depending on user preferences. And what did the end users make of it? I think there was excitement about the possibility of this both being less effortful, as well as the potential for it to reach faster communication rates. Even though the systems like this that are built on using attempted speak are quite a bit faster than some of the previous options available, they're still not quite at the speed of typical conversation.

7:10I think the fastest study published has reached about 90 words per minute, whereas typical conversational speech is closer to 150 words per minute. So this sort of inner speech decoding may be a way to reach those conversational rates of speech. And notably, at least a few of our participants have expressed the enthusiasm about the ability to potentially interrupt a conversation. Now, given that what you've effectively got here is a system that can hear a person's thoughts inside their head, potentially, that there might be things they say and they didn't actually want the computer to hear it.

7:46is there an ethical angle to this as well and were any of your participants or anybody in the study uncomfortable about the fact that you're now probing something that previously would be completely private to a person so yes we wanted to responsibly address this question and i will point out that we've also looked in to comparing the sort of inner speech representation to attempted speech and that there is strong distinguishability between those two and we've actually proposed two methods in the paper for addressing this in ways that the system can either totally ignore inner speech altogether if someone's using a system based on attempted speech or else a password that will allow the user to control when the decoder is running.

8:31So you can sort of think of that as saying hey Siri or hey Alexa and if it doesn't receive that command And first, it just ignores. So there's like a wake word for the interface. So the person can divorce themselves from having their thoughts read when they want a private moment. Yes. Amazing that, isn't it? But how long will it be before everyone has a system like that running in their heads? Interesting idea, isn't it? Erin Kunz there from Stanford University. Her study just came out in the journal Cell. Obesity researchers in London have found that eating ultra-processed foods makes it harder to lose weight.

9:10These foods are manufactured for convenience and tastiness, which can in turn make them more palatable and hence harder to resist. They also often contain high levels of sugar, salt and saturated fat. So a new study, which has been published in Nature Medicine, sought to discover to what extent this might be hindering weight loss among consumers who are seeking to slim down. Study participants ate meals prepared using either ultra-processed or minimally processed ingredients. And guess what? The diet comprising the minimally processed food turns out to be much more beneficial from a weight loss perspective.

9:45Here's Sam Dickin at University College London. So we've seen growing evidence around higher intakes of ultra-processed foods. These are foods that are made with the purpose of being highly profitable. So they're very cheap, accessible and tasty. And what are you coming back for more? Typically, these foods are very nutritionally poor, but actually some of these ultra-processed foods are nutritionally better. And no one's actually looked yet at whether ultra-processed foods that meet our current dietary guidance can be healthy. So we put that to the test. How did you test it? The best way to test diets and interventions is to do a clinical trial.

10:18So we gave participants a healthy balanced diet based on the current NHS guidance. That's having your five portions of fruit and veg day, not eating too many foods high in saturated fat, sugar and salt, and having the recommended fiber intakes. We provided these diets, one ultra-processed and one minimally processed. So these are the kinds of meals that you make from scratch at home with raw ingredients. And they were provided for free, delivered twice a week to participants' homes. We removed all these barriers that people face when accessing a healthy diet. So we provided it for free, ready prepared and with a menu guide.

10:50And what we wanted participants to do was to have as much or as little as they wanted of these diets. Because we think ultra-processed food for people to eat more than they need. So we're going to test that in the context of the current dietary guidance. Were the people trying to lose weight or gain weight? What was their health status before you started on this trial? So our participants were living with overweight or obesity. So that's the body mass index between 25 and 40 kilograms per meter squared. So it's your weight divided by your height squared. And the average person in the UK has a BMI of around 26 to 27.

11:22And participants were not told that at the trial we're looking at weight as the primary outcome, our main outcome of interest. and participants were not told to restrict their intake. We provided more energy than they needed in abundance of these two healthy balanced diets and they were just told to eat as much or as little as they wanted until they felt satisfied and full. So basically you're presenting these people for one period of time with a really wholesome healthy diet made from minimally processed foods that they would want to eat and then the rest of the trial you're doing the same thing but with ultra processed ingredients and the outcome measure is does their weight change?

11:56Exactly that. So the one diet minimally processed, the kind of foods you think of as typically healthy, then the ultra processed diet might be high fibre breakfast cereals, nutritionally improved sandwiches and meal deals, ready meals and snack bars, but all meeting our current guidance. So what happened then? Did you see a difference? Really interestingly, we saw that on both diets, people ate less than they were before they started the trial. Most probably because the diets they were eating before weren't aligned with our current dietary guidance they were eating too much saturated fat sugar and salt and not enough fruit and veg these nutritionally improved diets whether ultra processed or minimally processed resulted in significant weight loss what's really interesting is when participants had the minimally processed diet they lost twice as much weight significantly more weight loss than the ultra processed diet this is really interesting so ultra processed foods are not necessarily awful then they can in the right hands and mouths translate into a loss of weight but they're still not as good as if you make food from scratch i mean that's the take home from this then it is indeed and a good way to think about this is not all ultra processed foods are intrinsically unhealthy but there's an effect when that food has had the purpose of being made to be highly profitable tasty cheap and accessible we tend to see that there's a an effect on how much we eat and weight change compared to the same food if it wasn't going through this same process.

13:20Did the participants eat roughly the same amounts on both diets or did they lose more weight on the minimally processed foods because they ate less of it because actually they enjoyed it less? There were two ways we estimated their energy intakes on the trial. We asked them through dietary reports which can sometimes be a bit inaccurate because people tend to under-report. The other way is that we based it on the amount of changing their muscle mass and fat mass that changed across the diets and we saw that there was a significant reduction in their energy intake on the ultra-processed diet from baseline but a significantly greater reduction in their energy intake on the minimally processed diet compared to baseline and the ultra-processed diet.

13:58What's the take home from this then as opposed to take away I suppose you could say we've got a population of the world actually that are overweight and obese at extreme levels now and we're trying to combat this what does this study add what should people do differently? We know that the biggest barriers to accessing healthy food is cost. In the UK, the lowest 20 % of people in terms of income have to spend 70 % of their disposable income to meet our current dietary guidance, compared to 10 % of the highest 20 % of income. And that was reported in the Food Foundation Broken Plate report earlier this year.

14:33So what we need to do is clearly our current dietary guidance works, but it seems to be more favourable. We get greater weight loss and other aspects when it's a minimally processed diet. So we need higher level action from governments to change the financial drivers that dominate our food supply and rather than just being purely driven by profit also have health and the environment as stakeholders so we're developing foods that are incentivized to improve our health and not just our back pockets so at the moment someone who goes into a convenience store and they're hungry because it's the end of the day they've got a family to feed they're in a hurry they're going to reach for the ultra processed ready meals and so on because that's the easy option it's also often the cheaper option if we can flip that round you're saying and this study kind of suggests so that we're eating more minimally processed ingredients and making more meals from scratch which are at the moment more expensive so if we could make them cheaper and therefore there would be a price incentive to consume them more you're arguing that would be a double win because we would be healthier and the weight loss that people would achieve or at least not gaining as much weight would be greater.

15:42Indeed it seems to be a more cost-effective approach to improving diets and globally we see that it's a lack of healthy food so fruits, vegetables, whole grains, fibre that's linked with early mortality and greater disease and the more so than unhealthy components. We really need to think about how we're improving access to healthy foods but not by individuals by systems and governments and communities. Fascinating. So if you want to lose weight, avoid the process stuff and go back to dietary basics. That's the bottom line. Sam Dickin at University College London there. You know that feeling when too many things fall through the cracks?

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16:36The Naked Scientist podcast is produced in association with Spitfire, cost-effective voice, internet and IP engineering services for UK businesses. Find out how Spitfire can empower your company at spitfire.co.uk. Music in the programme is sponsored by Epidemic Sound, perfect music for audio and video productions. This is The Naked Scientist with me, Chris Smith. Still to come, how butterflies are inspiring superior solar solutions. But first, a PhD student at Imperial College London says he's found a way to use existing scientific tools already on board the current fleet of Mars rovers to search for active life on the red planet.

17:19Solomon Hirsch says the discovery could avoid the need for costly new missions to our celestial near neighbour. Well, the work we have here is some work we did on the equipment in our lab that closely replicates the equipment that's used on the surface of Mars. And we found that this equipment is able to distinguish between living and dead things, basically. So we've not found any evidence of life yet. But if we do, one of the first questions is, is it living now or is it dead? And hopefully the signals that we've detected in these experiments will help us answer that question in the future. Had the people who built the analytical instruments on the rovers not realised that this was what they could do then?

18:00I have read previous mission statements that have said that this ability is lacking. And it comes with some limitations, the main one being that we don't know what life is going to be like beyond Earth. We're really making the massive assumption here that it's similar to Earth. It's the best assumption we have. You know, we might think things might have evolved in similar ways on other planets. So we're not saying this is 100 % perfect test for all life, but with the best information we've got and using the equipment that we know that works, I think, yeah, we have discovered a new way that this equipment can be used.

18:36What is the signal that you think you can look for then? We started by looking at these molecules that are found in the membranes of most cells on Earth. So if these molecules aren't there, the membrane can't form and the cell will die. And when a cell dies, these membranes break down very quickly, mainly because they're eaten by other things. So these are a really good marker of living things because they break down really quickly when something's dead. So if they're there, then we expect that something is alive. We took these compounds and put them through our system and tried to see whether there was any distinctive signal of these compounds compared to the compounds that you get after something's died.

19:15And we found a few particular compounds that could distinguish these compounds that are indicative of living things. What are the chemicals? They're called intact polar lipids, and they are long chains of carbon. And one end is positively charged and the other end is negatively charged. And that kind of charge distribution causes these quite large molecules to arrange themselves into a membrane. A lot of them contain phosphate or phosphorus, not all of them. And in fact, our signal doesn't rely on the phosphorus. It just relies on the kind of most standard arrangement of these compounds. And how do you see them?

19:59As in what instrument on the rovers and what instrument in your lab enables you to see them? And with what sort of sensitivity? Very good question. It's something called a GCMS, which is gas chromatography mass spectrometry. Very long winded. when I first used it, it just seemed like a magic machine. You put something in and it tells you what it is. I couldn't believe it existed. It works very well for organic chemicals, especially, which because life is based on organic chemicals, are one of the main targets for astrobiology. The mass spectrometer part is probably the most intuitive to understand.

20:33We're trying to find the mass of the molecule, basically. And then from that, we can figure out what the compound is. and rovers like curiosity have got these devices aboard and therefore could go looking for these compounds that you say are indicative of a life process because if they break down so quickly if they're there something must be actively making them exactly yeah it's been used many times before the viking landers had this gcms equipment curiosity had it the exo-mars the mission that's launching in a few years time will have it as well the dragonfly mission titan will also have it so So it's well tested in space and we know it can work in those environments.

21:12And the sensitivity? We know this equipment works. We know this signal should be there if something is living. And the sensitivity should be high. We need to do more work to specifically give you a number on that sensitivity. But this equipment has been used at very high sensitivities. And you can even tune the equipment. Now we know what we're looking for. You can tune it to give you a high sensitivity if you know what you're looking for. Have you spoken to the mission teams to see if you can get this integrated into the experiments and just start sniffing around to see what's there? If you find some evidence of biology somewhere else in the solar system, I think, to my mind, that's just immediately, is it living now or is it dead?

21:49So it will become useful once we kind of reach that threshold of, OK, this looks like a biological signal. Now can we tell whether it's living or dead? And if we had a bigger programme budget, we would probably cue in a bit of music from David Bowie at that point, wouldn't we? That was Solomon Hirsch. he's at Imperial College London and his study has just come out in Nature Space Exploration. In the hunt for sustainable energy, solar power has emerged as a front-runner supplying much of the world's energy needs. Indeed, the sun sends us energy at the rate of more than 150 ,000 trillion watts and that's about 10 ,000 times the rate of what we're currently using.

22:24So we just need to become better at capturing it and using it. And if we could do that in a way that makes solar panels blend in a bit better too. What's not to like? Well, it turns out that maybe we can, and maybe we can do it with the help of three species of butterfly. We'll tingle. There can be no doubt that solar panels offer a cheap and decentralised way of generating energy, but there are always improvements to be made when it comes to getting the most power out of each panel. That's where our first two butterflies come into play. The more light you can get to hit a panel, the more energy you can produce.

23:01Thanks to work supported by UK Research and Innovation, we can take inspiration from nature to channel more light towards these solar nodules. To find out more, I've been speaking with the University of Exeter's Katie Shanks. When we think about nature, it's probably the ultimate trial and error. We wanted to make very lightweight optics and butterfly wings do that perfectly. And was there a particular species that you focused on? So I started looking at the cabbage white butterfly, which has very lightweight reflective wings. And then I also started looking at the glass wing butterfly, which has opposite properties.

23:38So it's very transparent, very anti-reflective. And so in that way, I had two blueprints to help understand and develop our own optics for solar panels. So I think I see what you're getting at with the glass wing butterflies. Obviously, as the name suggests, they have these translucent wings. And if you're saying that they can absorb in light very well. That sounds pretty useful if you're a solar panel. But why did you go for cabbage whites? The cabbage white, it actually does this very interesting behaviour in the morning where it sunbathes with its wings in a V shape. And the V shape of the cabbage white's wings helps focus light onto its body, onto its flight muscles, so it can fly quicker than other butterflies would.

24:21And so if you're increasing the amount of energy, the amount of sunlight into your solar panel, you're increasing the amount of energy out without actually having to increase the solar panel material you're using. So it's the idea then that you can have kind of the best of both worlds there. If you have an outer sort of shape of this cabbage white reflecting the light in and then this glasswing butterfly structure on the solar panel itself, you've got this almost hyper concentration of light hitting the solar panel. Exactly. Obviously the butterflies themselves produce these structures with very specialized proteins in their wings that create certain shapes that can refract or reflect the light as they desire.

25:00That's probably not an option to use. So what materials are you using to try and replicate these effects? We're looking at, for example, the cabbage white butterfly, titanium dioxide material. For the glass wing butterfly, we're actually, I'm working with the collaborators at Pittsburgh for a university who can actually etch these structures into glass. Is this something you could apply to already created solar panels, or does this have to be a fresh new solar panel that needs producing? So that's a good question. So applying it to current solar panels is feasible. I guess the question would be, would you be uninstalling and installing a solar panel?

25:39And it would come down to how old that solar panel was, and if it was worthwhile, also upgrading the solar cell technology as well. Do you foresee this being something that could be rolled out worldwide? Is it versatile? Is it durable enough, do you think? So one of the interesting properties of these nanostructures, the glass-line nanostructures, is that they also have properties such as hydrophobic. So whenever water hits them, whenever rain hits them, it rolls off easily. In terms of durability, they shouldn't be any less durable than current solar panels. And in terms of rollout and scalability, we've already analysed how this technology will perform in different areas of the world.